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Copyright of Revista Brasileira de Engenharia Agricola e Ambiental - Agriambi is the property of Revista Brasileira de Engenharia Agricola e Ambiental and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Blue honeysuckle (Lonicera caerulea L.) is a deciduous shrub with perennial rootstock found in China. The objectives of this study were to explore the drought tolerance of blue honeysuckle, determine the effect of drought stress on two photosystems, and examine the mechanism of acquired drought tolerance. In this study, blue honeysuckle under four levels of simulated field capacity (100%, 85%, 75%, and 65% RH) was grown in split-root pots for drought stress treatment, for measuring the changes in chlorophyll content, photosynthetic characteristics, and leaf chlorophyll fluorescence parameters. The chlorophyll content of each increased under mild stress and decreased under moderate and severe stress. The net photosynthetic rate, transpiration rate, intercellular carbon dioxide concentration, and stomatal conductance of blue honeysuckle decreased with the increase in water stress. However, the water utilization rate and stomatal limit system increased under mild and moderate stress and decreased under severe stress. The maximum fluorescence (Fm), maximum photochemical efficiency, and quantum efficiency of photosystem II decreased with the decrease in soil water content, and the initial fluorescence increased significantly (p < 0.01). With the decrease in soil water content, the energy allocation ratio parameters decreased under severe drought stress. The main activity of the unit reaction center parameters first increased and then decreased. ABS/CSm, TRo/CSm, ETo/CSm, and REo/CSm gradually declined. After a comprehensive analysis, the highest scores were obtained under adequate irrigation (CK). Overall, we concluded that the water irrigation system of blue honeysuckle should be considered adequate. [ABSTRACT FROM AUTHOR]

Due to the scarcity of biological resources, desert areas are unable to achieve long-term carbon sequestration. Biological crust is a pioneer organism in desert areas and plays an important role in long-term carbon sequestration. However, the development of natural biological crust is slow. Clay plays an important role in the formation and development of biological crusts, and has a strong protective effect on soil organic carbon. Therefore, this paper explores the impact and mechanism of adding kaolin on the organic carbon of soil biological crust system, aiming to provide new solutions for the long-term carbon sink in desert areas. Through testing particle size, specific surface area and pore volume, chlorophyll a, chlorophyll fluorescence, microbial community, and soil organic carbon (SOC), it has been found that the addition of kaolin changed the physicochemical properties and microbial community structure of the system, promoted the growth of biochar, and strengthened the protective effect of the system on SOC. After 112 days of cultivation, the results show that the accumulation of SOC in the kaolin-based biological crust system increases to 145% of the algae inoculation group. [ABSTRACT FROM AUTHOR]

Limited attention has been given to the persistent impacts of diverse herbicides present in soil on the growth of successive crops in agricultural production. Therefore, the objective of this experiment is to thoroughly examine atrazine residues toxic reactions in lucern (Medicago sativa L.). This experiment aims to thoroughly investigate the toxic response of atrazine in lucern. Lucern sourced from Henan Seed Company in China. The study employed the soil addition method to investigate the impacts and correlations of diverse concentrations of atrazine herbicide residues with growth indicators, photosynthetic features, chlorophyll fluorescence parameters of lucern. The results showed that with the increase of atrazine residue (0.0-2.0 mg·kg-1), the plant height (PH), root length (RL), stem dry weight (SDW) and root dry weight (RDW) decreased to 81.8%, 81.7%, 92.3% and 85.2%, respectively. SPAD value, net photosynthetic rate (Pn), stomatal conductance (GS), transpiration rate (Tr), the PSII maximum quantum yield (Fv/Fo), maximum photochemical efficiency (Fv/Fm), actual photosynthetic efficiency (Y(II)), PSII coefficient of photochemical fluorescence quenching (qP) and photosynthetic electron transport rate (ETR) decrease by 62.1%, 83.4%, 84.1%, 95.7%, 76.8%, 11.8%, 84.5%, 46.1% and 63.1%, respectively. However, the intercellular carbon dioxide concentration (Ci) and non-photochemical quenching coefficient (NPQ) increased by 46.2% and 37.5%, respectively. Ci was positively correlated with Fv/Fo, Fv/Fm, qP, Y(II) and ETR (P<0.01), SPAD, Pn and Gs were significantly negatively correlated with Tr (P<0.01), were significantly positively correlated with Tr, Fv/Fo, Fv/Fm, qP, Y(II) and ETR (P<0.01). The potential toxicity risk of atrazine residues to plants was assessed by photosynthetic characteristics and chlorophyll fluorescence parameters. Although herbicide application is essential for food production, appropriate concentration management methods must be adopted to ensure the sustainable development of agricultural ecology. [ABSTRACT FROM AUTHOR]

Abstract [Objective] The study aims to further study the leaf morphology and chlorophyll fluorescence characteristics of Actinidia arguta under greenhouse cultivation conditions, and to explore the differences of leaf photomorphogenesis between greenhouse and open field cultivation. [Methods] In this experiment, the 5-year-old plants of A . arguta varieties ‘Jialv’ and ‘Kuilv’ were used as test materials to determine the relative chlorophyll content and chlorophyll fluorescence parameters of leaves at different leaf ages under greenhouse and open field cultivation conditions. The differences in photomorphogenesis and chlorophyll fluorescence characteristics under greenhouse and open field cultivation conditions were analyzed. [Results] The photomorphogenesis of A . arguta cultivated in greenhouse and open field was between 1- 40 d leaf age, and the fluorescence characteristics of the same variety under different cultivation conditions tended to be consistent. After flowering, the fluorescence characteristics of the same variety under different cultivation conditions were quite different. The leaf area of A . arguta cultivated in greenhouse was larger and the content of chlorophyll b was higher, which was tending to shade leaf characteristics. The performance parameters such as PIabs were significantly lower than those of open field cultivation. The absorption and capture ability of light energy was stronger, but the heat dissipation was higher. The energy used for electron transfer was lower than that of open field cultivation, and the chlorophyll fluorescence parameters showed adaptive changes to the environment. [Conclusion] The photomorphogenesis time of A . arguta leaves is 1-40 days after leaf expansion, that is, before flowering. The photomorphogenesis of A . arguta leaves in greenhouse cultivation is different from open field cultivation, and the photosynthetic capacity is decreased slightly with the increase of leaf area. Greenhouse cultivation changes in the chlorophyll fluorescence characteristics of leaves to a certain extent and reduces photosynthetic performance.

Abstract [Objective] The heat tolerance of Camellia attracts more attention due to its rich flower types and colors and long flowering period. Suitable evaluation methods and indexes can provide bases for the heat-tolerance identification, the discovery of heat-tolerance germplasm, and the breeding of new cultivars of Camellia. [Methods] C. uraku and ‘Wirlinga Cascade’ were used as reference materials, and 7 new cultivars of cluster-flowering camellia were selected as test materials. They were cut in vase. After shortterm (5 h) or long-term (7 d) high-temperature (42 ℃/35 ℃) treatment, changes of morphological and photosynthetic indexes were investigated and heat tolerance was evaluated comprehensively. [Results] (1) The contents of chlorophyll, carotenoid, and chlorophyll a/b, net photosynthetic rate (Pn), and stomatal conductance (Gs) of ‘Chuizhi Fenyu’ and ‘Wirlinga Cascade’ were increased. Their maximum photochemical efficiency of PSⅡ (Fv/Fm ), potential activity of PSⅡ (Fv/Fo), and electron transport rate (ETR) were remained at a high level. Additionally, they did not show signs of heat damage after 7 days of high temperatures. Pn and Gs of ‘Jinye Fenyu’, ‘Shangzhi Huazhang’, and ‘Meigui Chun’ were decreased significantly under high temperature stress, while intercellular CO2 concentration (Ci) was increased. Among them, the Fv/Fm, Fv/Fo, and ETR of ‘Jinye Fenyu’ and ‘Shangzhi Huazhang’ were significantly reduced. After 7 days of long-term high temperature stress, these 3 cultivars showed severe heat damage or became dead. (2) 15 individual indicators were converted into 4 independent comprehensive indicators with cumulative contribution rate of 90% through principal component analysis. The comprehensive weight values of chlorophyll content, carotenoid content, and xanthophyll content were higher at 5 h under high temperature stress, and the comprehensive weight values of chlorophyll a/b, Fv/Fm, photochemical quenching coefficient (qP), and non-photochemical quenching coefficient (qN) were higher at 7 d under high temperature stress. [Conclusion] According to the comprehensive evaluation value D , ‘Chuizhi Fenyu’ is a heat-tolerance cultivar, ‘Shangzhi Yueguangqu’, ‘Shangzhi Huanlesong’, and ‘Sweet Gem’ are moderate tolerance, and ‘Meigui Chun’, ‘Shangzhi Huazhang’, and ‘Jinye Fenyu’ are the weakest among the new cultivars of cluster-flowering camellia. Chlorophyll, carotenoid, and xanthophyll contents can be used as the key indicators to analyze the short-term high temperature stress, while chlorophyll a/b, Fv/Fm, qP, and qN can be used as the key indicators to analyze the long-term high temperature stress of Camellia.

Rodents, such as those that feed on plants and nest in plant roots, can significantly affect the growth and development of desert plants. The aim of this study was to investigate the effects of Rhombomys opimus disturbance on the photosynthetic characteristics and nutrient status of Haloxylon ammodendron at different growth stages in the Gurbantunggut Desert. The effects of great gerbil disturbance on the photosynthetic characteristics of H. ammodendron at different growth stages were investigated by measuring the gas exchange parameters, instantaneous water use efficiency, and chlorophyll fluorescence parameters of H. ammodendron at different ages (young, middle, and adult) under the disturbance of great gerbils. The soil nutrients in the assimilated branches and rhizosphere of H. ammodendron at different growth stages were tracked to reveal the relationship between the H. ammodendron nutrient content and gerbil disturbance. The results showed that great gerbil disturbance decreased the organic carbon content in the rhizosphere soil of adult H. ammodendron and increased the total nitrogen content in the rhizosphere soil and the nitrogen and potassium contents in the assimilated branches at each growth stage. The net photosynthetic rate and instantaneous water use efficiency of H. ammodendron decreased at each growth stage, and the maximum photochemical efficiency and non-photochemical quenching parameters of the young H. ammodendron decreased. However, the actual photochemical efficiency and photochemical parameters of the middle H. ammodendron increased. It was concluded that the disturbance of great gerbils decreased the photosynthetic capacity of H. ammodendron and increased the content of total nitrogen in the soil and nitrogen and potassium in the plant. This study revealed that the Gurbantunggut Desert great gerbil and H. ammodendron do not have a simple predation relationship. It laid a foundation for the study of the moderate disturbance threshold and better use of the mutually beneficial relationship between the two. [ABSTRACT FROM AUTHOR]

Simple Summary: The experiment was conducted to investigate the effects of Bacillus subtilis on the growth and photosynthetic system of cucumber seedlings under different potassium levels. The pot experiment was conducted with "Xinjin 4" as the test material, and the two-factor experiment was designed. The two factors were different concentrations of potassium ion and Bacillus subtilis treatment. The effects of different treatments on growth, photosynthetic characteristics, root morphology and chlorophyll fluorescence parameters of cucumber seedlings were studied. The results showed that Bacillus subtilis had the most significant effect on cucumber seedling growth and leaf photosynthesis when the concentration of potassium ion was 0.2 g/pot. This study provided a theoretical basis for further utilizing Bacillus subtilis to make microbial fertilizer and improve the nutrient absorption efficiency of cucumber to promote the development of agriculture. Potassium deficiency is one of the important factors restricting cucumber growth and development. This experiment mainly explored the effect of Bacillus subtilis (B. subtilis) on cucumber seedling growth and the photosynthetic system under different potassium levels, and the rhizosphere bacteria (PGPR) that promote plant growth were used to solubilize potassium in soil, providing theoretical support for a further investigation of the effect of biological bacteria fertilizer on cucumber growth and potassium absorption. "Xinjin No. 4" was used as the test material for the pot experiment, and a two-factor experiment was designed. The first factor was potassium application treatment, and the second factor was bacterial application treatment. The effects of different treatments on cucumber seedling growth, photosynthetic characteristics, root morphology, and chlorophyll fluorescence parameters were studied. The results showed that potassium and B. subtilis had obvious promotion effects on the cucumber seedling growth and the photosynthesis of leaves. Compared with the blank control, the B. subtilis treatment had obvious effects on the cucumber seedling height, stem diameter, leaf area, total root length, total root surface area, total root volume, branch number, crossing number, gs, WUE, Ci, and A; the dry weight of the shoot and root increased significantly (p ≤ 0.05). Potassium application could significantly promote cucumber growth, and the effect of B. subtilis and potassium application was greater than that of potassium application alone, and the best effect was when 0.2 g/pot and B. subtilis were applied. In conclusion, potassium combined with B. subtilis could enhance the photosynthesis of cucumber leaves and promote the growth of cucumber. [ABSTRACT FROM AUTHOR]

Zinc (Zn) is an essential trace element but can lead to water contamination and ecological deterioration when present in excessive amounts. Therefore, investigating the photosynthetic response of microalgae to Zn stress is of great significance. In this study, we assessed the photosynthetic responses of neutrophilic Chlamydomonas reinhardtii and acidophilic Chlamydomonas sp. 1710 to Zn exposure for 96 h. The specific growth rate (μ), chlorophyll-a (Chl-a) content, and chlorophyll fluorescence parameters were determined. The results demonstrated that Chlamydomonas sp. 1710 was much more tolerant to Zn than C. reinhardtii, with the half-maximal inhibitory concentration (IC50) values of 225.4 mg/L and 23.4 mg/L, respectively. The μ and Chl-a content of C. reinhardtii decreased in the presence of 15 mg/L Zn, whereas those of Chlamydomonas sp. 1710 were unaffected by as high as 100 mg/L Zn. Chlorophyll fluorescence parameters indicated that the regulation of energy dissipation, including non-photochemical quenching, played a crucial role in Zn stress resistance for both Chlamydomonas strains. However, in the case of C. reinhardtii, non-photochemical quenching was inhibited by 5 mg/L Zn in the first 48 h, whereas for Chlamydomonas sp. 1710, it remained unaffected under 100 mg/L Zn. Chlamydomonas sp. 1710 also exhibited a 20 times stronger capacity for regulating the electron transfer rate than C. reinhardtii under Zn stress. The light energy utilization efficiency (a) of Chlamydomonas sp. 1710 had the most highly non-linear correlation with μ, indicating the energy utilization and regulation process of Chlamydomonas sp. 1710 was well protected under Zn stress. Collectively, our findings demonstrate that the photosystem of Chlamydomonas sp. 1710 is much more resilient and tolerant than that of C. reinhardtii under Zn stress. [ABSTRACT FROM AUTHOR]

To investigate the regulatory effects of exogenous Bacillus velezensis(B. v. ) on seed germination, seedling growth and photosynthetic system of maize, Zhengdan 958 and Jingnongke 728 were used as test materials for inoculation with B. v. . the results showed that:Compared with CK, exogenous application of B. v. significantly promoted maize seed shoot germination and effectively increased seedling height, leaf area, fresh weight, dry weight and root to crown ratio. Compared with Bacillus bacteria agent, B. v. treatment had a significant advantage in promoting maize seed germination, and the indexes related to agronomic traits such as plant height, leaf area, dry weight and fresh weight were also not significantly different from those of Bacillus bacteria agent. Compared to CK, maize seedlings under exogenous B. v. treatment showed significantly higher Pn, Tr, Gs and WUE and significantly lower Ci compared to CK. Pn, Tr and Gs under B. v. treatment were not significantly different from Bacillus bacteria agent treatment, but significantly weaker than Bacillus mycoflora in terms of Ci utilization efficiency. Compared with CK, exogenous application of B. v. helped to enhance chlorophyll content and improve fluorescence characteristics in maize seedling leaves: significantly enhanced chlorophyll a, chlorophyll b, chlorophyll a / b,the total chlorophyll content, Fm, Fv / Fm, Fv / Fo and qP, and significantly reduced Fo and NPQ. The chlorophyll content and total content of leaves under B. v. treatment were significantly higher than those under Bacillus bacteria agent treatment, and the fluorescence parameters were not significantly different from Bacillus bacteria agent treatment overall, and some indexes were even better than Bacillus bacteria agent treatment. Therefore, Bacillus velezensis has a good development prospect and application value on corn, and has the potential to be further developed into a new type of bacterial agent. [ABSTRACT FROM AUTHOR]

Foxtail millet planting has a long history and profound role in agricultural civilization. However, weeds have become one of the obstacles restricting the development of the foxtail millet industry. Penoxsulam, as an early post-emergence herbicide for controlling gramineous weeds in paddy fields, is effective for some broadleaf weeds. In this study, six different doses (CK, 0.5X, 1X, 2X, 3X, 4X) of penoxsulam were sprayed at the 3–5 leaf stage of the conventional variety Jingu 21 to study its effect on the growth and development of foxtail millet, in order to screen out the appropriate spraying concentration. The main results are as follows: Within 15 days after spraying penoxsulam, the plant height and leaf area of foxtail millet decreased with the increase in spraying dose, and gradually recovered 15–25 days after spraying, but there were still significant differences compared with CK. The photosynthetic pigment content, net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), the maximum photochemical efficiency (Fv/Fm), photosynthetic system II actual photochemical efficiency (Y(II)), and photochemical quenching coefficient (qP) of foxtail millet decreased with an increase in the penoxsulam spraying dose, while the intercellular CO2 concentration (Ci) and non-photochemical quenching coefficient (NPQ) showed an upward trend. There was almost no significant difference in each index between the spraying dose of 0.5X and 1X and CK, but the photosynthesis of foxtail millet leaves was still significantly inhibited under a spraying dose of 3X and 4X. Penoxsulam had certain growth-inhibiting effects on Echinochloa crus-galli (L.) Beauv. (E. crus-galli), Digitaria sanguinalis (L.) Scop. (D. sanguinalis), Chenopodium album L. (C. album), and Amaranthus retroflexus L. (A. retroflexus) which increased as the spraying dosage increased. Our study found that spraying dose groups of 0.5X and 1X penoxsulam were safe for foxtail millet growth and could be used to control gramineous weeds in fields. Other spraying doses are not recommended in the field due to their serious phytotoxicity to foxtail millet, which provides a new measure for weed control in foxtail millet fields. [ABSTRACT FROM AUTHOR]

[ Objective ] Salt stress leads to poor growth and development and decreased ornamental quality of Chinese rose ( Rosa chinensis Jacq. ), and seriously affects their outdoor greening applications in high salt environments or coastal areas. This study explores the effects of exogenous melatonin ( MT ) and inoc- ulation with arbuscular mycorrhizal fungi ( AMF ) on seedling growth , chlorophyll fluorescence parame- ters , and cytokinin metabolism , and analyzes their physiological and the biochemical mechanisms that pro- mote rose to adapt to salt stress , in order to enhance salt resistance and expand the application of rose. [ Methods ] The seedling of Chinese rose variety ‘ Yueyue Hong ’ was used as experimental material to con- duct indoor potting experiments. In addition , control ( CK ), 100 mol / L NaCl stress , root administration of MT , and root inoculation of AMF larvae of the genus Claroideoglomus etatunicum and their combina- tion were set to investigate the effects of each treatment on the growth of rose seedlings , chlorophyll fluo- rescence parameters , hormone metabolism , and antioxidant system. [ Results ] ( 1 ) Application of MT pro- moted AMF infestation of the roots of rose seedlings and increased the infection rate , bush growth rate , number of vesicles , and invasion points. ( 2 ) Under salt stress , the growth of rose seedlings was inhibited , and plant height , stem thickness , and biomass were decreased significantly. MT and AMF treatments in- creased the height , stem thickness , and biomass of rose seedlings , whereas AMF+MT treatment had no significant difference in plant height and stem thickness , aboveground dry weight and underground dry weight were increased by 24.1% and 37.0%. ( 3 ) Under salt stress , the chlorophyll content of rose seed- lings was decreased significantly while chlorophyll fluorescence parameters were decreased , and MT and AMF treatments could improve the chlorophyll content and chlorophyll fluorescence parameters. Under AMF+MT treatment , the total amount of chlorophyll and chlorophyll a / b was increased by 46.2% and 67.2% , respectively. PSⅡ maximum photochemical efficiency ( F v / F m ), potential activity ( F v / F o ), ac- tual photochemical efficiency ( Φ PSⅡ ), effective photochemical quantum efficiency ( F v ' / F m ' ), and photo- chemical quenching coefficient ( q P ) were increased by 4.9% , 51.0% , 175.0% , 168.7% , and 92.5% , re- spectively , whereas NPQ was decreased by 42.7%. ( 4 ) Under salt stress , zeatin ( ZT ), gibberellin ( GA ), auxin ( IAA ) content in leaves were decreased , whereas the abscisic acid ( ABA ) content was in- creased. MT and AMF contributed to the increase in ZT , GA , and IAA content and the decrease in ABA content. Under AMF+MT treatment , ZT , GA , and IAA content were increased by 146.9% , 116.9% , 35.7% , respectively , while ABA was decreased by 21.1%. ( 5 ) Under salt stress , the activity of SOD and CAT were increased , and the rate of superoxide anions ( O - · 2 ) production and H 2 O 2 accumulation was in- creased. MT and AMF treatments decreased O - · 2 production rate and H 2 O 2 content , while AMF+MT treatment activated SOD and CAT activity , and reduced the rate of O - · 2 production and H 2 O 2 accumula- tion. [ Conclusion ] Inoculation with AMF , addition of MT , or AMF+MT treatment could increase the chlorophyll content of rose seedlings under salt stress , protect the chlorophyll fluorescence system , main- tain the balance of endogenous plant hormones , activate the activity of antioxidant enzymes such as SOD and CAT , and reduce lipid peroxidation and H 2 O 2 accumulation , thereby reduce the damage caused by salt stress to rose seedlings , promote rose growth , and enhance the salt resistance of rose seedlings better with AMF+MT treatment.

To evaluate the Ca-alleviating effect on sodium salt-induced phytotoxicity, wheat (Triticum aestivum L.) cultivar Xihan 3 seedlings were treated with 150 mM NaCl, CaCl2 (0.1, 0.5, and 1 mM), Ca2+-channel blocker LaCl3, and/or Ca2+ chelator, ethylene glycol tetraacetic acid (EGTA) alone or in combination, to investigate seedling growth and photosynthetic characteristics. NaCl (150 mM) exposure alone suppressed a growth of seedling, weakened photosynthetic efficiency and chlorophyll (Chl) fluorescence parameters, reduced photosynthetic pigments, Ca2+ and calmodulin (CaM) contents, and downregulated TaCaM expression in wheat leaves. The opposite changes of these parameters were caused by 0.5 or 1 mM CaCl2 treatments alone. Moreover, 0.5 or 1 mM CaCl2 application effectively alleviated sodium salt-induced changes of these parameters, which was blocked by LaCl3 or EGTA. Therefore, exogenous Ca presence effectively promoted the growth of NaCl-stressed wheat seedlings through the enhancement of photosynthesis and Chl synthesis mediated by the Ca-CaM signal.

To reveal the impact of cadmium stress on the physiological mechanism of lettuce, simultaneous determination and correlation analyses of chlorophyll content and photosynthetic function were conducted using lettuce seedlings as the research subject. The changes in relative chlorophyll content, rapid chlorophyll fluorescence induction kinetics curve, and related chlorophyll fluorescence parameters of lettuce seedling leaves under cadmium stress were detected and analyzed. Furthermore, a model for estimating relative chlorophyll content was established. The results showed that cadmium stress at 1 mg/kg and 5 mg/kg had a promoting effect on the relative chlorophyll content, while cadmium stress at 10 mg/kg and 20 mg/kg had an inhibitory effect on the relative chlorophyll content. Moreover, with the extension of time, the inhibitory effect became more pronounced. Cadmium stress affects both the donor and acceptor sides of photosystem II in lettuce seedling leaves, damaging the electron transfer chain and reducing energy transfer in the photosynthetic system. It also inhibits water photolysis and decreases electron transfer efficiency, leading to a decline in photosynthesis. However, lettuce seedling leaves can mitigate photosystem II damage caused by cadmium stress through increased thermal dissipation. The model established based on the energy captured by a reaction center for electron transfer can effectively estimate the relative chlorophyll content of leaves. This study demonstrates that chlorophyll fluorescence techniques have great potential in elucidating the physiological mechanism of cadmium stress in lettuce, as well as in achieving synchronized determination and correlation analyses of chlorophyll content and photosynthetic function. [ABSTRACT FROM AUTHOR]

Copyright of Xinjiang Agricultural Sciences is the property of Xinjiang Agricultural Sciences Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To evaluate the Ca-alleviating effect on sodium salt-induced phytotoxicity, wheat (Triticum aestivum L.) cultivar Xihan 3 seedlings were treated with 150 mM NaCl, CaCl2 (0.1, 0.5, and 1 mM), Ca2+-channel blocker LaCl3, and/or Ca2+ chelator, ethylene glycol tetraacetic acid (EGTA) alone or in combination, to investigate seedling growth and photosynthetic characteristics. NaCl (150 mM) exposure alone suppressed a growth of seedling, weakened photosynthetic efficiency and chlorophyll (Chl) fluorescence parameters, reduced photosynthetic pigments, Ca2+ and calmodulin (CaM) contents, and downregulated TaCaM expression in wheat leaves. The opposite changes of these parameters were caused by 0.5 or 1 mM CaCl2 treatments alone. Moreover, 0.5 or 1 mM CaCl2 application effectively alleviated sodium salt-induced changes of these parameters, which was blocked by LaCl3 or EGTA. Therefore, exogenous Ca presence effectively promoted the growth of NaCl-stressed wheat seedlings through the enhancement of photosynthesis and Chl synthesis mediated by the Ca-CaM signal. [ABSTRACT FROM AUTHOR]

The objective of the study is to investigate the mechanism by which summer pruning enhances the growth of pepper plants, as indicated by growth and fruit appearance indicators, photosynthetic rate and gas exchange parameters, rapid light response and induction kinetics curves and the related chlorophyll fluorescence parameters. The results indicated that the leaf growth rate, the individual pepper fruit weight, and the fruit longitudinal and cross diameters of the pruned group were significantly higher than those of the control. The stomatal conductance (Gs), intercellular CO2 concentration (Ci) and transpiration rate (Tr) of the pruned group were significantly higher than those of the control. The initial slope of the rapid light response curve, which represents light energy utilisation efficiency (a), the maximum electron transfer rate (Jmax) and saturated light intensity (PARsat) were all higher in the summer pruning group than in the control group. The F0 of the pruned group decreased by 16.83%, Fv/F0 increased by 23.69%, PIabs increased by 58.33%, and DIo/RC decreased by 22.09% compared to the control group. In summary, summer pruning significantly improves the leaf growth rate and fruit appearance quality of pepper, effectively promotes the photosynthesis of functional leaves, and reduces the degree of stress under adverse environmental conditions. [ABSTRACT FROM AUTHOR]

Blue honeysuckle (Lonicera caerulea L.) is a deciduous shrub with perennial rootstock found in China. The objectives of this study were to explore the drought tolerance of blue honeysuckle, determine the effect of drought stress on two photosystems, and examine the mechanism of acquired drought tolerance. In this study, blue honeysuckle under four levels of simulated field capacity (100%, 85%, 75%, and 65% RH) was grown in split-root pots for drought stress treatment, for measuring the changes in chlorophyll content, photosynthetic characteristics, and leaf chlorophyll fluorescence parameters. The chlorophyll content of each increased under mild stress and decreased under moderate and severe stress. The net photosynthetic rate, transpiration rate, intercellular carbon dioxide concentration, and stomatal conductance of blue honeysuckle decreased with the increase in water stress. However, the water utilization rate and stomatal limit system increased under mild and moderate stress and decreased under severe stress. The maximum fluorescence (Fm), maximum photochemical efficiency, and quantum efficiency of photosystem II decreased with the decrease in soil water content, and the initial fluorescence increased significantly (p < 0.01). With the decrease in soil water content, the energy allocation ratio parameters decreased under severe drought stress. The main activity of the unit reaction center parameters first increased and then decreased. ABS/CSm, TRo/CSm, ETo/CSm, and REo/CSm gradually declined. After a comprehensive analysis, the highest scores were obtained under adequate irrigation (CK). Overall, we concluded that the water irrigation system of blue honeysuckle should be considered adequate.

Copyright of Xinjiang Agricultural Sciences is the property of Xinjiang Agricultural Sciences Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Agricultural Science & Technology (1008-0864) is the property of Journal of Agricultural Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Introduction: Chilling injury is one of the most common meteorological disasters affecting cucumber production. For implementing remedial measures as soon as possible to minimize production loss, a timely and precise assessment of chilling injury is crucial. Methods: To evaluate the possibility of detecting cucumber chilling injury using chlorophyll fluorescence (ChlF) technology, we investigated the continuous changes in ChlF parameters under various low-temperature conditions and created the criteria for evaluating chilling injury. The ChlF induction curves were first collected before low-temperature as unstressed samples and daily 1 to 5 days after low-temperature as chilling injury samples. Principal component analysis was employed to investigate the public information on ChlF parameters and evaluate the differences between samples with different degrees of chilling injury. The parameters (Fv/Fm, Y(NO), qP, and Fo) accounted for a large proportion in the principal components and could characterize chilling injury. Uniform manifold approximation and projection method was employed to extract new features (Feature 1, Feature 2, Feature 3, and Feature 4) from ChlF parameters for subsequent classification model. Taking four features as input, a classification model based on the Fuzzy C-means clustering algorithm was constructed in order to identify the chilling injury classes of cucumber seedlings. The cucumber seedlings with different chilling injury classes were analyzed for ChlF images, rapid light curves, and malondialdehyde content. Results and discussion: The results demonstrated that the variations in these indicators among the different chilling injury classes supported the validity of the classification model. Our findings provide a better understanding of the relationship between ChlF parameters and the impact of low-temperature treatment on cucumber seedlings. This finding offers an additional perspective that can be used to evaluate the responses and damage that plants experience under stress. [ABSTRACT FROM AUTHOR]

Rodents, such as those that feed on plants and nest in plant roots, can significantly affect the growth and development of desert plants. The aim of this study was to investigate the effects of Rhombomys opimus disturbance on the photosynthetic characteristics and nutrient status of Haloxylon ammodendron at different growth stages in the Gurbantunggut Desert. The effects of great gerbil disturbance on the photosynthetic characteristics of H. ammodendron at different growth stages were investigated by measuring the gas exchange parameters, instantaneous water use efficiency, and chlorophyll fluorescence parameters of H. ammodendron at different ages (young, middle, and adult) under the disturbance of great gerbils. The soil nutrients in the assimilated branches and rhizosphere of H. ammodendron at different growth stages were tracked to reveal the relationship between the H. ammodendron nutrient content and gerbil disturbance. The results showed that great gerbil disturbance decreased the organic carbon content in the rhizosphere soil of adult H. ammodendron and increased the total nitrogen content in the rhizosphere soil and the nitrogen and potassium contents in the assimilated branches at each growth stage. The net photosynthetic rate and instantaneous water use efficiency of H. ammodendron decreased at each growth stage, and the maximum photochemical efficiency and non-photochemical quenching parameters of the young H. ammodendron decreased. However, the actual photochemical efficiency and photochemical parameters of the middle H. ammodendron increased. It was concluded that the disturbance of great gerbils decreased the photosynthetic capacity of H. ammodendron and increased the content of total nitrogen in the soil and nitrogen and potassium in the plant. This study revealed that the Gurbantunggut Desert great gerbil and H. ammodendron do not have a simple predation relationship. It laid a foundation for the study of the moderate disturbance threshold and better use of the mutually beneficial relationship between the two.

Potassium deficiency is one of the important factors restricting cucumber growth and development. This experiment mainly explored the effect of Bacillus subtilis (B. subtilis) on cucumber seedling growth and the photosynthetic system under different potassium levels, and the rhizosphere bacteria (PGPR) that promote plant growth were used to solubilize potassium in soil, providing theoretical support for a further investigation of the effect of biological bacteria fertilizer on cucumber growth and potassium absorption. “Xinjin No. 4” was used as the test material for the pot experiment, and a two-factor experiment was designed. The first factor was potassium application treatment, and the second factor was bacterial application treatment. The effects of different treatments on cucumber seedling growth, photosynthetic characteristics, root morphology, and chlorophyll fluorescence parameters were studied. The results showed that potassium and B. subtilis had obvious promotion effects on the cucumber seedling growth and the photosynthesis of leaves. Compared with the blank control, the B. subtilis treatment had obvious effects on the cucumber seedling height, stem diameter, leaf area, total root length, total root surface area, total root volume, branch number, crossing number, gs, WUE, Ci, and A; the dry weight of the shoot and root increased significantly (p ≤ 0.05). Potassium application could significantly promote cucumber growth, and the effect of B. subtilis and potassium application was greater than that of potassium application alone, and the best effect was when 0.2 g/pot and B. subtilis were applied. In conclusion, potassium combined with B. subtilis could enhance the photosynthesis of cucumber leaves and promote the growth of cucumber.

In order to explore the responses of growth, photosynthetic characteristics and nutrient accumulation of Cunninghamia lanceolata container seedlings to different amounts of slow-release fertilizer application. In this paper, the effects of different amounts of slow-release fertilizer application treatments (0, 200, 400, 800, 1 000 and 1 200 g·m-3) on the growth of seedlings height, ground diameter, biomass, photosynthetic pigment content, chlorophyll fluorescence characteristics and nutrient content of C. lanceolata seedlings were investigated. Moreover, subordinate function value method was also employed to comprehensive evaluate the growth and physiology indexes of seedlings under different fertilization treatments, and screening suitable slow-release fertilizer levels for the growth of C. lanceolata seedlings, which providing reference for the efficiency cultivation of high quality C. lanceolata seedlings. The results were as follows: (1) Compared with the control, the slow-release fertilizer application could promote the growth of seedling height, ground diameter and the accumulation of total biomass of C. lanceolata seedlings to varying degrees. (2) The slow-release fertilizer treatments could significantly increase the contents of chlorophyll and carotenoid in leaves of C. lanceolata compared with control. In addition, slow-release fertilizer treatments also increased the values of maximum fluorescence(Fm), variable fluorescence(Fv), maximum photochemical efficiency of PS Ⅱ(Fv/Fm), potential photochemical efficiency of PS Ⅱ(Fv/Fo) and actual quantum yield(QY) to varying degrees compared with control. (3) The slow-release fertilizer treatments could promote the nutrient accumulation in seedlings of C. lanceolata to varying degrees, among which the contents of Mn, Fe and Zn were found to be changed most significantly. (4) The results of subordinate function value method showed that when the amount of slow-release fertilizer application was 1 000 g·m-3, its membership value was the largest, which indicated that the comprehensive growth of seedlings under this treatment was the best. In conclusion, the amount of 1 000 g·m-3 slow-release fertilizer application is the most suitable treatment for the cultivation of high quality seedlings of C. lanceolata in the present study, under this treatment, the growth of C. lanceolata seedlings can be improved by increasing the accumulation of nutrient elements closely related to photosynthesis, thus increasing the contents of photosynthetic pigment in leaves, which in turn enhance the PS Ⅱ photosynthetic efficiency and electron transfer rate, further enhance the efficiency of light energy capture and utilization of leaves, and ultimately improve seedling growth.

Sargassum thunbergii is distributed on reefs and rock marshes in mid- and low-tide zones, and some are periodically exposed to lengthy low tides. Dehydration is a key factor affecting the survival of S. thunbergii at low tides. In this study, using wild S. thunbergii as experimental material, the water loss rate, chlorophyll fluorescence parameters, and biochemical parameters under different stresses were determined by dehydrating the thalli in an incubator for 0, 1, 3, and 6 h. The results showed that: (1) algae of different sizes have significantly different water loss rates under different stresses. The shorter the stress time and the larger the algae, the lower the water loss rate, indicating that the water retention capacity of S. thunbergii with larger thalli is higher. Wild S. thunbergii grow in clusters on reefs. The leaves in the lower part of the branches and near the holdfast are wide. The middle and upper leaves are narrow and long, respectively. The lower broad leaves are easily blocked by the upper branches. Therefore, differences in the growth environment cause differences in the ecological structure and biochemical components of S. thunbergii. High temperature, strong light, and water loss at low tide are the main factors that cause severe environmental stress to sessile S. thunbergii in the intertidal zone. (2) Dehydration significantly reduced the chlorophyll fluorescence value of S. thunbergii, and different parts of the same individual of S. thunbergii had significantly different tolerance to dehydration, with the lowest tolerance at branch tips and the strongest tolerance at the base. The non-regulatory energy-dissipation mechanism plays a major role in the dehydration response of S. thunbergii. Under dry exposure, the light energy utilization efficiency of S. thunbergii was significantly reduced. This reduction in active light protection capacity indicates that dehydration reduces the adaptability of S. thunbergii to excessive light intensity. Dehydration can damage the tips of small individuals that cannot recover, while the base part of large individuals could return to a normal physiological state. (3) Antioxidant enzymes (ASAFR, SOD) and non-antioxidant substances (soluble sugar and proline) in the tip part responded to dehydration, and the base part mainly responded by upregulation of protein, soluble sugar, and proline content to resist stress. S. thunbergii, located in the high and middle tide zones, is more likely to be stressed by high temperatures, strong light, and dehydration, and the physiological and biochemical characteristics of different parts of the thallus are also variable due to differences in external morphology. Algae mainly reduce damage to the photosynthetic system caused by a lack of water through a non-regulatory energy dissipation mechanism. The water retention capacity of the base was better than branch tips during dry exposure, and the damage to algal cells was low. The main roles are as heat shock proteins, soluble sugars, proline, and other small molecules, which can pass stress response, osmotic regulation, and anti-oxidation resists damage to cells caused by stress. The water retention capacity of the top cells was weak, and the stress was relatively strong. Antioxidant enzymes such as ASAFR and SOD in algae and non-antioxidant enzymes such as soluble sugars and proline, work together to resist dry exposure stress, reduce cell damage and maintain cell viability. In summary, under the stress of dry exposure, the antioxidant enzymes, antioxidant substances, and non-regulatory energy dissipation mechanisms of S. thunbergii play a role in maintaining cell activity. This study provides important guidance for exploring the ecological adaptability of S. thunbergii in resisting environmental stress.

[Objectives] This paper aimed to study the expression pattern of BCGR2. 1 in non-heading Chinese cabbage under photooxidative stress, and explore the effects of BcGR2.1 overexpression or silencing on the plant resistance to photooxidative stress, so as to clarify the function of the gene. [Methods] The CDS sequence of BcGR2. 1 gene was cloned from non-heading Chinese cabbage, and the phylogenetic tree analysis and conserved domain alignment of the amino acid sequence encoded by BcGR2.1 were performed. The expression level of BcGR2. 1 under photooxidative stress was analyzed by RT-qPCR. BcGR2. 1-overexpressing Arabidopsis thaliana and BcGR2. 1-silencing plants were obtained by Agrobacterium-mediated floral dip transformation and virus- induced gene silencing (VIGS) respectively, the effects of overexpression or silencing of BcGR2. 1 on the plant resistance to photooxidative stress were also tested. [Results] BcGR2.1 gene contained a 1 626 bp open reading frame (ORF), and had the closest evolutionary relationship with Brassica rapa. The expression level of BeGR2. 1 was up-regulated and then down-regulated under photooxidative stress induced by methyl viologen (MV) treatment. The content of ascorbic acid (AsA) increased in overexpression transgenic A. thaliana and decreased in BcGR2. I-silencing plants. Under photooxidative stress, H2O2 content was significantly lower in overexpression transgenic A. thaliana than that in wild type, while H2O2 content in BcGR2. 1-silencing plants was significantly higher than that in PTY empty plants. The chlorophyll fluorescence kinetics parameters such as FY/Fm Y(II), ETR and qP were significantly higher in BcGR2.1-overexpressing A. thaliana than those in wild type. [Conclusions] BcGR2.1 had positive regulation on AsA content in A. thaliana and non-heading Chinese cabbage, inhibited the H2O2 explosion under photooxidative stress, maintained the normal state of chlorophyll fluorescence parameters, and improved the tolerance of plants to photooxidative stress. [ABSTRACT FROM AUTHOR]

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Pine wood nematode disease is a destructive disease to the ecological environment and forest resources. The disease is produced by Bursaphelenchus xylophilus, and the onset rate is extremely fast and the pathogenesis of the disease is not clear. Prevention of this disease is still important in production, so it is of great significance to explore its early diagnosis. In this study, the changes of chlorophyll fluorescence dynamic induction parameters, non-photochemical quenching parameters and organic acid content in needles of 7-year-old-infected Pinus hwangshanensis were studied by chlorophyll fluorescence technology and organic acid mass combined technology. The results showed that in the chlorophyll fluorescence dynamic induction group, Fm/Fo, Fv/Fo, Fm, Psi_o and Pi_Abs showed a significant downward trend, while Phi_Do, ABS/RC, TRO/RC and DIO/RC showed a significant uptrend. In non-photochemical quenching, Fm showed a downward trend, while Qp_L1, Qp_L2, QY_L1, QY_L2 and QY_Lss showed a significant upward trend. In the change of organic acid content, ferulic acid, syringic acid, gallic acid and jasmonic acid showed a significant increasing trend, while benzoic acid and salicylic acid showed a first increasing trend and then decreasing trend. Experimental results show that pine wood nematode had significant effects on photosynthesis and the organic acid content of pine before it showed symptoms of the disease. After comprehensive analysis, chlorophyll fluorescence dynamic induction parameters Pi_Abs, Fm, Phi_Do, TRO/RC, Psi_o, non-photochemical quenching parameters QY_L2, Qp_L1, QY_Lss, QY_L1 and organic acids ferulic acid, syringic acid, benzoic acid and gallic acid contents are ideal indicators for early diagnosis of pine wood nematodiasis. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Northwest A & F University - Natural Science Edition is the property of Editorial Department of Journal of Northwest A&F University (Natural Science Edition) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Maize (Zea mays L.) is one of the most widely grown cereals in the world. Its cultivation is affected by abiotic stress caused by climate change, in particular, drought. Zinc (Zn) supplied by foliar nutrition can increase plant resistance to water stress by enhancing physiological and enzymatic antioxidant defence mechanisms. One of the possibilities to reduce the effect of drought on plant production is also the utilization of trehalose. In order to confirm the effect of the foliar application of selected forms of Zn (0.1% w/v solution)—zinc oxide micro- (ZnO) and nanoparticles (ZnONP), zinc sulphate (ZnSO4) and zinc chelate (ZnEDTA)—a pot experiment in controlled conditions was conducted in combination with trehalose (1% w/v solution) on selected growth parameters of maize exposed to the drought stress. A significant effect of coapplication of Zn and trehalose on chlorophyll content, chlorophyll fluorescence parameters, root electrical capacity, weight of maize aboveground biomass (AGB) and Zn content in AGB was found. At the same time, the hypothesis of a positive effect of carbohydrates on increasing the uptake of foliar-applied Zn was confirmed, especially for the ZnEDTA and ZnSO4. This paper presents the first empirical evidence of the trehalose addition to sprays for zinc foliar fertilization of maize proving to be an effective way of increasing the resistance of maize grown under drought stress conditions. [ABSTRACT FROM AUTHOR]

Foxtail millet planting has a long history and profound role in agricultural civilization. However, weeds have become one of the obstacles restricting the development of the foxtail millet industry. Penoxsulam, as an early post-emergence herbicide for controlling gramineous weeds in paddy fields, is effective for some broadleaf weeds. In this study, six different doses (CK, 0.5X, 1X, 2X, 3X, 4X) of penoxsulam were sprayed at the 3–5 leaf stage of the conventional variety Jingu 21 to study its effect on the growth and development of foxtail millet, in order to screen out the appropriate spraying concentration. The main results are as follows: Within 15 days after spraying penoxsulam, the plant height and leaf area of foxtail millet decreased with the increase in spraying dose, and gradually recovered 15–25 days after spraying, but there were still significant differences compared with CK. The photosynthetic pigment content, net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), the maximum photochemical efficiency (Fv/Fm), photosynthetic system II actual photochemical efficiency (Y(II)), and photochemical quenching coefficient (qP) of foxtail millet decreased with an increase in the penoxsulam spraying dose, while the intercellular CO2 concentration (Ci) and non-photochemical quenching coefficient (NPQ) showed an upward trend. There was almost no significant difference in each index between the spraying dose of 0.5X and 1X and CK, but the photosynthesis of foxtail millet leaves was still significantly inhibited under a spraying dose of 3X and 4X. Penoxsulam had certain growth-inhibiting effects on Echinochloa crus-galli (L.) Beauv. (E. crus-galli), Digitaria sanguinalis (L.) Scop. (D. sanguinalis), Chenopodium album L. (C. album), and Amaranthus retroflexus L. (A. retroflexus) which increased as the spraying dosage increased. Our study found that spraying dose groups of 0.5X and 1X penoxsulam were safe for foxtail millet growth and could be used to control gramineous weeds in fields. Other spraying doses are not recommended in the field due to their serious phytotoxicity to foxtail millet, which provides a new measure for weed control in foxtail millet fields.

To reveal the impact of cadmium stress on the physiological mechanism of lettuce, simultaneous determination and correlation analyses of chlorophyll content and photosynthetic function were conducted using lettuce seedlings as the research subject. The changes in relative chlorophyll content, rapid chlorophyll fluorescence induction kinetics curve, and related chlorophyll fluorescence parameters of lettuce seedling leaves under cadmium stress were detected and analyzed. Furthermore, a model for estimating relative chlorophyll content was established. The results showed that cadmium stress at 1 mg/kg and 5 mg/kg had a promoting effect on the relative chlorophyll content, while cadmium stress at 10 mg/kg and 20 mg/kg had an inhibitory effect on the relative chlorophyll content. Moreover, with the extension of time, the inhibitory effect became more pronounced. Cadmium stress affects both the donor and acceptor sides of photosystem II in lettuce seedling leaves, damaging the electron transfer chain and reducing energy transfer in the photosynthetic system. It also inhibits water photolysis and decreases electron transfer efficiency, leading to a decline in photosynthesis. However, lettuce seedling leaves can mitigate photosystem II damage caused by cadmium stress through increased thermal dissipation. The model established based on the energy captured by a reaction center for electron transfer can effectively estimate the relative chlorophyll content of leaves. This study demonstrates that chlorophyll fluorescence techniques have great potential in elucidating the physiological mechanism of cadmium stress in lettuce, as well as in achieving synchronized determination and correlation analyses of chlorophyll content and photosynthetic function.

In order to explore the responses of growth, photosynthetic characteristics and nutrient accumulation of Cunninghamia lanceolata container seedlings to different amounts of slow-release fertilizer application. In this paper, the effects of different amounts of slow-release fertilizer application treatments(0, 200, 400, 800, 1 000 and 1 200 g·m-3)on the growth of seedlings height, ground diameters, biomass, photosynthetic pigment content, chlorophyll fluorescence characteristics and nutrient content of C. lanceolata seedlings were investigated. Moreover, subordinate function value method was also employed to comprehensive evaluate the growth and physiology indexes of seedlings under different fertilization treatments, and screening suitable slow-release fertilizer levels for the growth of C. lanceolata seedlings, which providing reference for the efficiency cultivation of high quality C. lanceolata seedlings. The results were as follows:(1)Compared with the control, the slow-release fertilizer application could promote the growth of seedling height, ground diameter and the accumulation of total biomass of C. lanceolata seedlings to varying degrees.(2)The slow-release fertilizer treatments could significantly increase the contents of chlorophyll and carotenoid in leaves of C. lanceolata as compared with control. In addition, slow-release fertilizer treatments also increased the values of maximum fluorescence(Fm), variable fluorescence(Fv), maximum photochemical efficiency of PS Ⅱ(Fv/Fm), potential photochemical efficiency of PS Ⅱ(Fv/Fo)and actual quantum yield(QY)to varying degrees when compared with control.(3)The slow-release fertilizer treatments could promote the nutrient accumulation in seedlings of C. lanceolata to varying degrees, among which the contents of Mn, Fe and Zn were found to be changed most significantly.(4)The results of subordinate function value method showed that when the amount of slow-release fertilizer application was 1 000 g·m-3, its membership value was the largest, which indicated that the comprehensive growth of seedlings under this treatment was the best. In conclusion, the amount of 1 000 g·m-3 slow-release fertilizer application is the most suitable treatment for the cultivation of high quality seedlings of C. lanceolata in the present study, under this treatment, the growth of C. lanceolata seedlings can be improved by increasing the accumulation of nutrient elements closely related to photosynthesis, thus increasing the contents of photosynthetic pigment in leaves, which in turn enhance the PS Ⅱ photosynthetic efficiency and electron transfer rate, further enhance the efficiency of light energy capture and utilization of leaves, and ultimately improve seedling growth. [ABSTRACT FROM AUTHOR]

Ardisia japonica is a low ornamental shrub belong to myrsinacea family. It is widely used as a ground cover in gardens because of strong shade tolerance. It is of great significance to study the growth and adaptability of A. japonica in soils with different salt concentration for popularizing its landscaping in saline-alkali soil. The effects of different salts on triennial potted A. japonica seedlings were studied, with red-yellow soil, soil-coconut bran, and black soil (with a volume ratio: 1:1:1) as the substrate. Seven treatments were set, including CK, A1 (0.30%NaCl), A2 (0.60%NaCl), B1 (0.30%Na2CO3), B2 (0.60%Na2CO3), C1 (0.15%NaCl+0.15%Na2CO3) and C2 (0.30%NaCl+0.30%Na2CO3). The plant height, MDA, soluble protein, chlorophyll content and chlorophyll fluorescence parameters were measured. With the increasing of stress degree, the plant height increment and rhizome water content of A. japonica gradually decreased. Meanwhile, the cell membrane was damaged, and the permeability changed, and MDA, the main product of membrane lipid peroxidation increased accordingly. The soluble protein of A. japonica first increased and then decreased, which indicated that the protein would degrade when the stress reached a certain degree, low concentration of salt promoted promoted effect at the early stage of the stress. During the stress, the value of Fv´/Fm´, ETR, Fv/Fm decreased. The results showed that A. japonica had a certain salt tolerance, and A. japonica could be planted in areas containing mild neutral salt and mixed saline soil, which was not suitable for planting in alkaline salt areas. [ABSTRACT FROM AUTHOR]

【Objective】The article aimed to compare the leaf traits of nine common compositae weeds in Yunnan province, and explore the adaptability of different compositae weeds. 【Method】Nine common compositae weeds in Yunnan province were used as materials to measure the leaf traits, stoichiometric characteristics and chlorophyll fluorescence parameters. 【Result】There were significant differences in leaf anatomical characteristics, stomatal density, leaf vein density, leaf area and specific leaf area among the nine compositae weeds. The phosphorus(P) content(1.61-1.82 mg/g) was higher than the national average level of land plants, the nitrogen(N) content of other seven species(25.23-63.52 mg/g) except for Sonchus oleraceus and Artemisia annua was higher than the global average level of terrestrial plants, and Fv/Fm was more than 0.7 in all species which revealed good photosynthetic characteristics, therefore indicated that compositae weeds had good adaptability to the environment of Yunnan province. Comprehensive analysis of indigenous and invasive weeds showed that the variation coefficient of leaf traits in indigenous and invasive weeds was 2.51%-61.66% and 2.44%-80.89%, respectively. Different weeds possessed different adaptation strategies to the dry environment in Yunnan province. The invasive species Parthenium hysterophorus had the thickest cuticle(13.98 μm) and palisade tissue(145.57 μm), which were helpful to reduce water loss. However, the indigenous species S.oleraceus had the thickest epidermis(65.22 μm), the largest stomatal density(331.55 N/mm²) and leaf vein density(10.32 cm/cm²), which were helpful to reduce water dissipation, as well as improve transpiration regulation and water transport capacity to cope with dry environment.【Conclusion】The nine species of compositae weeds had good adaptability to the local environment in Yunnan province, and differences in leaf traits reflected differences in adaptive strategies of different compositae species to the dry environment in Yunnan province. The results would provide reference for the study of the adaptive mechanism and the control strategies of compositae weeds in Yunnan province. [ABSTRACT FROM AUTHOR]

Benzoapyrene (B[a]P) pollution poses a threat to the environment and the food chain and consequently to human health. However, the alleviation of the harmful effects of B[a]P pollution in perennial ryegrass (Lolium perenne L.) by the application of exogenous nitric oxide (NO) has been ignored. Thus, in this paper the effects of exogenous sodium nitroprusside (SNP, a NO donor) on the growth, photosynthetic fluorescence characteristics, and antioxidant enzyme activity of ryegrass exposed to B[a]P stress are investigated. B[a]P stress induced the reduction of the aboveground and belowground dry weights, chlorophyll (a, b), the total chlorophyll contents, the carotenoid content, the net photosynthetic rate (Pn), the intercellular carbon dioxide concentration (Ci), the water use efficiency (WUE), the photosystem II (PSII) potential activity (Fv/F0), the maximum quantum yield of PSII photochemistry (Fv/Fm), the steady-state fluorescence yield (Fs), and the non-photochemical quenching (qN), while enhancement was recorded in response to the foliar spray of SNP at 200 and 300 μmol L-1 under B[a]P stress. Gray correlation and principal component analyses show that 200 μmol L-1 of SNP more drastically alleviated the damage caused by B[a]P stress than 300 μmol L-1 of SNP. The exogenous NO-mediated alleviation of B[a]P toxicity in ryegrass was associated with preserved photosynthetic characteristics and activation of antioxidant enzymes. [ABSTRACT FROM AUTHOR]

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In recent years, heavy metal hazards in the soil have seriously affected agricultural production. This study aims to examine the effects of different levels of heavy metal Zn on the growth, photosynthesis and physiological characteristics of wheat, and provide a theoretical basis for the diagnosis and control of heavy metal pollution in agricultural production. The field test method was used to explore the changes of wheat agronomic traits, photosynthetic capacity, chlorophyll fluorescence parameters, spectral characteristic curve, active oxygen metabolism system, cell ultrastructure, and yield, under different Zn levels (0, 250, 500, 750, and 1 000 mg kg–1). The results show that, low-level Zn treatments can effectively promote the synthesis of wheat chlorophyll, improve photosynthetic capacity, and increase yield. The yield of ZnL1 (250 mg kg–1) was the highest in the two-year test, which increased by 20.4% in 2018 and 13.9% in 2019 compared with CK (0 mg kg–1). However, a high Zn level had a significant stress effect on the photosystem of wheat. PIabs (reaction center performance index) and Fv/Fm (maximum photochemical efficiency) were significantly reduced, the active oxygen metabolism system was damaged, and the photosynthetic capacity was reduced, which in turn led to reduced yield. Among them, the yield of ZnL4 (1 000 mg kg–1) was the lowest in the two-year test, which was 28.1 and 16.4% lower than CK in 2018 and 2019, respectively. The green peak position of ZnL3 and ZnL4 had “red shift” to the long wave direction, while the red valley position of ZnL4 had “blue shift” to the short wave direction. Under ZnL4, some wheat leaf organelles began to decompose, vacuoles increased, cytoplasm decreased, cell walls thickened, chloroplast basal lamellae were disordered, and mitochondrial membranes disintegrated. Stepwise regression and Path analysis showed that Pn (net photosynthetic rate) played a leading role in the formation of yield. Redundancy (RDA) analysis showed that the optimal Zn level for wheat growth was about 250 mg kg–1, and wheat would be stressed when the soil Zn level exceeded 500 mg kg–1 in the test condition of this study. Findings of this study provide a theoretical basis for the diagnosis and prevention of heavy metal (Zn) pollution in the soil.

It is a great challenge to identify different cucumber diseases at early stages based on conventional methods due to complex and similar symptoms. By contrast, chlorophyll fluorescence is an early indicator of membrane changes or disturbances during plant growth. This research aimed to propose an effective method for the identification of brown spot (BS) and anthracnose (AN) in cucumbers based on chlorophyll fluorescence imaging, and to interpret the relationship between fluorescence response and different diseases coupled with active oxygen metabolism analysis. Support vector machine (SVM) and eXtreme Gradient Boosting (XGBoost) were used to classify the different disease degrees of brown spot and anthracnose in cucumber plants. XGBoost is more effective for this study, with a classification accuracy greater than 90% for diseased cucumbers. Additionally, the XGBoost classification model was validated by the different disease degrees of cucumber plants, and the five-class classification accuracies were 88.2%, 85.0%, 75.0%, 65.0% and 75.0% for Healthy, BS-slight, BS-severe, AN-slight, and AN-severe, respectively. The diseased cucumbers had a higher level of reactive oxygen species (ROS) accumulation than the healthy cucumbers, and the activity levels of the ROS-scavenging enzymes of anthracnose were higher than those of brown spot. The analysis of fluorescence parameters and the discrimination model for different diseases were well linked to the active oxygen metabolism analysis. These results demonstrate the potential of chlorophyll fluorescence imaging combined with active oxygen metabolism analysis for the detection of cucumber diseases, regarding different disease types and disease degrees. [ABSTRACT FROM AUTHOR]

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The chlorophyll fluorescence parameter Fv/Fm plays a significant role in indicating the photosynthetic function of plants. The existing technical methods used to measure Fv/Fm are often inefficient and cumbersome. To realize fast and non-destructive monitoring of Fv/Fm, this study took rice under different fertilizer treatments and measured the hyperspectral reflectance information and Fv/Fm data of rice leaves during the whole growth period. Five spectral transformation methods were used to pre-process the spectral data. Then, spectral characteristic wavelengths were extracted by the correlation coefficient method (CC) combined with the competitive adaptative reweighted sampling (CARS) algorithm. Finally, based on the combination of characteristic wavelengths extracted from different spectral transformations, back propagation neural network (BPNN) models were constructed and evaluated. The results showed that: (1) first derivative transform (FD), multiplicative scatter correction (MSC) and standardized normal variation (SNV) methods could effectively highlight the correlation between spectral data and Fv/Fm. The most sensitive bands with high correlation coefficients were concentrated in the range of 650–850 nm, and the absolute values of the highest correlation coefficients were 0.84, 0.73, and 0.72, respectively. (2) The CC-CARS algorithm could effectively screen the characteristic wavelengths sensitive to Fv/Fm. The number of sensitive bands extracted by FD, MSC, and SNV pre-treatment methods were 14, 13, and 16 which only accounted for 2.33%, 2.16%, and 2.66% of the total spectral wavelength (the number of full spectral bands is 601), respectively. (3) The BPNN models were established based on the above sensitive wavelengths, and it was found that MSC-CC-CARS-BPNN had the highest prediction accuracy, and its testing set R2, RMSE and RPD were 0.74, 1.88% and 2.46, respectively. The results can provide technical references for hyperspectral data pre-processing and rapid and non-destructive monitoring of chlorophyll fluorescence parameters. [ABSTRACT FROM AUTHOR]

Plant growth and development are strongly influenced by light quality conditions in their environment. In this study, in vitro shoot proliferation, photosynthetic pigments, leaf anatomy and photosystem II photochemistry of Gisela 6 cherry rootstock (Prunus cerasus x Prunus canescens) were investigated. The culture medium used was the MS (Murashige and Skoog) containing 4.4 μΜ 6-benzyladenine (BA), 0.05 μΜ α-naphthalene acetic acid (NAA) and 0.3 μM gibberellic acid (GA3) (30 days, 16 h photoperiod, 22 ± 2 °C). Initially, two different light wavelength absorption spectra: 400–700 nm provided by white fluorescent light lamps (mainly blue–green, BG at equal ratio 1:1; WFL-40) and, 430–690 nm provided by two Light Emitting Diodes (LED) types, differing in the spectral ratio of multiple light emitting wavelengths [LED2-40 (blue–red, BR) and LED3-40 (blue–green–yellow–orange–red, BGYOR)] were studied, under 40 μmol m−2 s−1 of light intensity. Following that, three LED intensities-20 (LED1-20), 40 (LED2-40), and 120 μmol m−2 s−1 (LED4-120) were investigated under BR spectrum. WFL-40 exhibited non-significant differences with LED2-40 (shoot number 4.25, proliferation rate 4.30, shoot height 0.91 cm). LED2-40 displayed higher fresh and dry shoot biomass, better PSII functionality, increased Chl a/b, Chl b and carotenoids content as well as decreased number of stressed explants. Leaf anatomy under LED2-40 and WFL-40 was similar. LED4-120 presented the highest rate of stressed explants, with their leaf anatomy being severely affected, as leaves had a reduced mesophyll cell density. In LED4-120, the proportion of the absorbed energy used in photochemistry (ΦPSII) was decreased whereas the increased quantum yield of non-regulated energy loss in PSII (ΦNO) could not be compensated by the increased photoprotective energy dissipation (ΦNPQ). Therefore, LED2-40 is proposed as the most beneficial for growing cherry rootstock Gisela 6 plantlets in vitro. Key Message: Higher proliferation rate, shoot biomass, photosystem II functionality, Chl a/b and carotenoids under LED2-40 (BR) [430–690 nm, mainly blue-red at a 1:3 ratio, 40 μmol m−2 s−1] whereas high light stress [LED4-120 (BR)] (120 μmol m−2 s−1) adversely affected leaf anatomy. [ABSTRACT FROM AUTHOR]

In the present study, hyperspectral imaging and remote sensing of fluorescence were integrated to monitor the nitrogen content in leaves of drip-irrigated cotton at different growth periods in northern Xinjiang, China. Based on the spectrum and chlorophyll fluorescence parameters of nitrogen content in cotton leaves of different growth periods obtained through the shuffled frog-leaping algorithm (SFLA), the successive projection algorithm (SPA), grey relational analysis (GRA), and competitive adaptive reweighted sampling (CARS), a monitoring model of nitrogen content in cotton leaves was established via on hyperspectral imaging, chlorophyll fluorescence parameters, and spectral-fluorescence data fusion. The results showed that: (1) there were significant positive correlations between the chlorophyll fluorescence parameters Fv'/Fm', Fv/Fm, Yield, Fm, NPQ, and the nitrogen content at each growth period. (2) The effectiveness of chlorophyll fluorescence parameters in inversion of nitrogen content was the highest at the budding period and the blooming period, and the coefficients of determination (R2) of the validation sets were 0.745 and 0.709, respectively. (3) In the monitoring model for cotton leaf nitrogen in the blooming period that was established based on the decisionlevel algorithm and spectral-fluorescence data fusion, the R2 value of the training set reached 0.961, and that of the validation set was 0.828. In conclusion, the findings of this study suggest that the feature-level fusion and decision-level fusion algorithms of spectral-fluorescence data can effectively improve the accuracy and reliability of cotton leaf nitrogen monitoring. [ABSTRACT FROM AUTHOR]

As the most severe forestry quarantine disease in several countries, pine wilt disease (PWD) causes substantial economic losses and poses a significant threat to the forest ecosystem. It is necessary to find a rapid and sensitive method for the early diagnosis of the disease to control the development of the disease effectively. This paper investigated the effect of Bursaphelenchus xylophilus (the pinewood nematode; PWN) on the chlorophyll fluorescence kinetic curve (OJIP curve) and the parameters of needles using four-year-old Pinus thunbergii as experimental materials and chlorophyll fluorescence analysis as a technical tool. It was shown by the results in the OJIP curve that the fluorescence intensity of the inoculated plants was significantly increased at points O and I. Additionally, the relative variable fluorescence intensity at points K and J was comparable to that of the control plants. Several chlorophyll fluorescence parameters of the treatment significantly increased or decreased with disease progression. At the same time, the control group had no significant changes in each parameter. Therefore, chlorophyll fluorescence parameters can be used as indicators for the early diagnosis of PWD, among which the DIo/RC parameter was the best. In summary, PWN invasion will produce fluorescence on the PSII of P. thunbergii, and its chlorophyll fluorescence parameters are expected to achieve early PWD diagnosis. [ABSTRACT FROM AUTHOR]

The spontaneous combustion of coal gangue dumps after reclamation causes severe harm to the ecological environment surrounding mining areas. Using remote sensing technology to determine vegetation heat stress levels is an important way to evaluate the probability of a spontaneous combustion disaster. The canopy spectra and chlorophyll fluorescence (ChlF) parameters of alfalfa were collected through pot experiments to simulate different heat stress levels. Time series analyses of three ChlF (chlorophyll fluorescence) parameters showed that the regularity of the quantum efficiency of photosystem II (PSII) in light-adapted conditions ( Fv ′ / Fm ′ ) was stronger during the monitoring period. The correlation coefficients between the three ChlF parameters and the canopy raw spectrum, first derivative spectrum, and vegetation indices were calculated, and the spectral features were found to be more correlated. Lasso regression was used to further screen spectral features, and the optimal spectral features were the raw spectral value at 741 nm (abbreviated as RS (741)) and NDVI (652, 671). To discriminate among heat stress levels accurately and automatically, we built a time convolution neural network. The classification results showed that when the sequence length is 3, the heat stress is divided into three categories, and the model obtains the highest accuracy. In combination with relevant research conclusions on the temperature distribution law of spontaneous combustion in coal gangue dumps, three heat stress levels can be used to assess the potential of spontaneous combustion in coal gangue dumps after reclamation. The research results provide an important theoretical basis and technical support for early warnings regarding spontaneous combustion disasters in reclaimed coal gangue dumps. [ABSTRACT FROM AUTHOR]

This study focused on the physiological regulation and mechanism of exogenous 5-aminolevulinic acid (5-ALA) in the late growth of P. heterophylla. In the middle of May, different concentrations of 5-ALA (0, 10, 20, 50 mg·L−1) were sprayed on the leaves. The effects of 5-ALA on tuberous root growth, antioxidant enzyme system, gas exchange, photosynthetic pigment contents and photosynthetic characteristics were measured from 23 May to 13 June. A concentration of 20 mg·L−1 of 5-ALA led to a significant increase in the yield of fresh root and biomass allocation at 38.12% and 25.07%, respectively, in comparation with the control (0 mg·L−1). The moderate concentration of 5-ALA statistically stimulated antioxidation activities. 5-ALA treatment enhanced photosynthetic activity and reduced photodamage. Compared to the control, there were increases in the chlorophyll fluorescence parameters of P. heterophylla under 5-ALA treatment. Moreover, 20 mg·L−1 of 5-ALA significantly changed the kinetic parameters of fluorescence. It enhanced the light absorption and distribution efficiency of PSII and the activities of leaves, resulting in alleviating photoinhibition by the excess excitation energy. The correlation indicated that there was a significant positive correlation between the yield of tuberous roots and biomass allocation, Pn and catalase (CAT), and a negative correlation between the yield of tuberous roots and malondialdehyde (MDA). The appropriate 5-ALA concentration in the late growth stage of P. heterophylla effectively enhanced the net photosynthetic capacity, mainly resulting from the enhancement of PSII photochemical activity to promote the increases in excitation energy absorption, capture and electron transfer efficiency of the leaves. Finally, 5-ALA treatment can increase the photochemical activity of PSII in the whole leaf and ultimately delay the senescence of P. heterophylla. [ABSTRACT FROM AUTHOR]

Soybean is an important legume food crop, and its seeds are rich in nutrients, providing humans and animals with edible oil and protein feed. However, soybean is sensitive to water requirements, and drought is an important factor limiting soybean yield and quality. This study used Heinong 84 (drought resistant variety) and Hefeng 46 (intermediate variety) as tested varieties planted in chernozem, albic, and black soils. The effects of drought stress on the activities of key enzymes in carbon metabolism and photosynthetic characteristics of soybean were studied during the flowering stage, most sensitive to water. (1) The activities of SS-1, 6PGDH, and G6PDH enzymes in soybean leaves first increased and then decreased under drought stress. The enzyme activity was the highest under moderate drought stress and weakest in the blank group. (2) Drought stress increased Phi2, PhiNO, and Fm in soybean leaves and reached the highest value under severe drought; with the increase in drought stress, PhiNPQ and Fv/Fm of soybean leaves gradually decreased, reaching the lowest under severe drought. (3) With the increase in drought stress, F0 and Fs of soybean leaves showed a single peak curve, and the maximum was at moderate drought. (4) Correlation analysis showed that F0 was greatly affected by varieties and soil types; Fs, F0, and Fm soil varieties had a great influence, and chlorophyll fluorescence parameters were affected differently under drought stress with different drought degrees. (5) Drought stress changed the agronomic traits and yield of soybean. With the increase of drought degree, plant height, node number of main stem, effective pod number, 100-seed weight and total yield decreased continuously. (6) Drought stress affected the dry matter accumulation of soybean. With the increase of drought degree, the dry matter accumulation gradually decreased. Among them, the leaf was most seriously affected by drought, and SD decreased by about 55% compared with CK. Under the condition of black soil, the dry matter accumulation of soybean was least affected by drought. [ABSTRACT FROM AUTHOR]

Treatment and recycling of high concentrations of ammonia nitrogen (NH4+–N) and tatal phosphorus (TP) is a major challenge in today's wastewater industry, while microalgae not only captures CO2, but also provide a safe and cost-effective alternative to wastewater treatment according to its growth characteristics. However, we found that excessive NH4+–N is harmful to microalgae. Significantly higher accumulation rate of the biomass and chlorophyll, as well as removal rate of ammonia nitrogen and phosphorus were observed in an acclimated strain of Chlorella vulgaris (HPN-3#) compared to those of the original strain (CK). The results of photosynthetic performance indicated that although photosystem of both strains were inhibited by the stress of high concentration of NH4+–N. The photosynthetic efficiency of HPN-3# was also higher than that of CK. The results of chlorophyll fluorescence transients and parameters suggested that HPN-3# showed better performance of energy flux regulation and electron transportation that mitigates NH4+–N inhibition, whereas the mixotrophic cultivation strategy using additional carbon source also reduced the stress and helped to maintain the accumulation of microalgae. In addition, acidified environment has a negative effect on the luxury uptake of P, and subsequently reduced its removal efficiency. [ABSTRACT FROM AUTHOR]

Soil salinization effects plant photosynthesis in a number of global ecosystems. In this study, photosynthetic and physiological parameters were used to elucidate the impacts of saline-alkaline stress on Cyperus esculentus L. (C. esculentus) seedling photosynthesis. The results demonstrate that salt stress, alkali stress and mixed salt and alkali stress treatments all have similar bell-shaped influences on photosynthesis. At low concentrations (0−100 mmol L−1), saline-alkaline stress promoted net photosynthetic rate, transpiration rate and water use efficiency in C. esculentus. However, as the treatments increased in intensity (100−200 mmol L−1), plant photosynthetic parameters began to decline. We interpreted this as the capacity of C. esculentus to improve osmoregulatory capacity in low saline-alkaline stress treatments by accumulating photosynthetic pigment, proline and malondialdehyde to counterbalance the induced stress – an adaptive mechanism that failed once concentrations reached a critical threshold (100 mmol L−1). Stomatal conductance, maximum photosynthetic rate and actual photosynthetic rate all decreased with increasing concentration of the stress treatments, and intercellular carbon dioxide showed a decreasing and then increasing trend. These results indicated that when the saline-alkaline stress concentrations were low, C. esculentus seedlings showed obvious adaptive ability, but when the concentration increased further, the physiological processes of C. esculentus seedlings were significantly affected, with an obvious decrease in photosynthetic efficiency. This study provides a new understanding of the photosynthetic adaptation strategies of C. esculentus seedlings to varying concentrations of saline-alkaline stress. • Photosynthesis in C. esculentus did not differ under saline-alkaline stress. • At low levels, C. esculentus adapted photosynthetically, showing salt tolerance. • Stomatal limitation is the dominant factor of low stress in C. esculentus seedlings. • High concentration impairs C. esculentus photosynthesis mechanisms. [ABSTRACT FROM AUTHOR]

Pine wood nematode disease is a destructive disease to the ecological environment and forest resources. The disease is produced by Bursaphelenchus xylophilus, and the onset rate is extremely fast and the pathogenesis of the disease is not clear. Prevention of this disease is still important in production, so it is of great significance to explore its early diagnosis. In this study, the changes of chlorophyll fluorescence dynamic induction parameters, non-photochemical quenching parameters and organic acid content in needles of 7-year-old-infected Pinus hwangshanensis were studied by chlorophyll fluorescence technology and organic acid mass combined technology. The results showed that in the chlorophyll fluorescence dynamic induction group, Fm/Fo, Fv/Fo, Fm, Psi_o and Pi_Abs showed a significant downward trend, while Phi_Do, ABS/RC, TRO/RC and DIO/RC showed a significant uptrend. In non-photochemical quenching, Fm showed a downward trend, while Qp_L1, Qp_L2, QY_L1, QY_L2 and QY_Lss showed a significant upward trend. In the change of organic acid content, ferulic acid, syringic acid, gallic acid and jasmonic acid showed a significant increasing trend, while benzoic acid and salicylic acid showed a first increasing trend and then decreasing trend. Experimental results show that pine wood nematode had significant effects on photosynthesis and the organic acid content of pine before it showed symptoms of the disease. After comprehensive analysis, chlorophyll fluorescence dynamic induction parameters Pi_Abs, Fm, Phi_Do, TRO/RC, Psi_o, non-photochemical quenching parameters QY_L2, Qp_L1, QY_Lss, QY_L1 and organic acids ferulic acid, syringic acid, benzoic acid and gallic acid contents are ideal indicators for early diagnosis of pine wood nematodiasis.