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Many studies have investigated the photoprotective and photosynthetic capacity of plant leaves, but few have simultaneously evaluated the dynamic changes of photoprotective capacity and photosynthetic maturation of leaves at different developmental stages. As a result, the process between the decline of photoprotective substances and the onset of photosynthetic maturation during plant leaf development are still poorly understood, and the relationship between them has not been quantitatively described. In this study, the contents of photoprotective substances, photosynthetic pigment content and photosynthetic capacity of leaves at different developmental stages from young leaves to mature leaves were determined by spatio-temporal replacement in eight dominant tree species in subtropical evergreen broadleaved forests. The correlation analysis found that the data sets of anthocyanins, flavonoids, total phenolics and total antioxidant capacity were mainly distributed on one side of the symmetry axis (y  =  x), while the data sets of flavonoids, total phenolics and total antioxidant capacity were mainly distributed on both sides of the symmetry axis (y  =  x). In addition, the content of photoprotective substances in plant leaves was significantly negatively correlated with photosynthetic pigment content and photosynthetic capacity but was significantly positively correlated with dark respiration rate (Rd). When chlorophyll accumulated to ~50% of the final value, the photoprotective substance content and Rd of plant leaves reached the lowest level, and anthocyanins disappeared completely; in contrast, the photosynthetic capacity reached the highest level. Our results suggest that anthocyanins mainly play a light-shielding role in the young leaves of most plants in subtropical forests. In addition, 50% chlorophyll accumulation in most plant leaves was the basis for judging leaf photosynthetic maturity. We also believe that 50% chlorophyll accumulation is a critical period in the transition of plant leaves from high photoprotective capacity (high metabolic capacity, low photosynthetic capacity) to low photoprotective capacity (low metabolic capacity, high photosynthetic capacity). [ABSTRACT FROM AUTHOR]

Abstract: Morphological, structural, and eco-physiological features of roots, nutrient removal, and correlation between the indices were comparatively studied for 35 emergent wetland plants in small-scale wetlands for further investigation into the hypothesis of two types of wetland plant roots (). Significant differences in root morphological, structural, and eco-physiological features were found among the 35 species. They were divided into two types: fibrous-root plants and thick-root plants. The fibrous-root plants had most or all roots of diameter (D) ≤ 1 mm. Roots of D > 1 mm also had many fine and long lateral roots of D ≤ 1 mm. The roots of these plants were long and had a thin epidermis and a low degree of lignification. The roots of the thick-root plants were almost all thicker than 1 mm, and generally had no further fine lateral roots. The roots were short, smooth, and fleshy, and had a thick epidermis. Root porosity of the fibrous-root plants was higher than that of the thick-root plants (p = 0.001). The aerenchyma of the fibrous-root plants was composed of large cavities which were formed from many small cavities, and distributed radially between the exodermis and vascular tissues. The aerenchyma of the thick-root plants had a large number of small cavities which were distributed in the mediopellis. The fibrous-root plants had a significantly larger root biomass of D ≤ 1 mm, of 1 mm < D < 3 mm, above-ground biomass, total biomass, and longer root system, but shorter root longevity than those of the thick-root plants (p = 0.003, 0.018, 0.020, 0.032, 0.042, 0.001). The fibrous-root plants also had significantly higher radial oxygen loss (ROL), root activity, photosynthetic rate, transpiration rate, and removal rates of total nitrogen and total phosphorus than the thick-root plants (p = 0.001, 0.008, 0.010, 0.004, 0.020, 0.002). The results indicate that significantly different root morphological and structural features existed among different wetland plants, and these features had a close relationship to nutrient removal capacity. [Copyright &y& Elsevier]

Abstract: The aim of this study was to compare the growth, community structure, and nutrient removal rates between monoculture and mixed wetlands, based on the hypothesis that it depends on the plant species used in the wetlands as to whether monoculture or mixed wetland is superior in plant growth and nutrient removal. Pilot-scale monoculture and mixed constructed wetlands were studied over 4 years. The monoculture wetland had a community height similar to the mixed wetland during the early years but a significantly lower height than the mixed wetland (P <0.05) during the last year. The mixed wetland also displayed a higher plant density than the monoculture wetland (P <0.05). The leaf area index in the monoculture wetland was significantly higher in the first year (P <0.05) and significantly lower in the later years (P <0.05) than that in the mixed wetland. The monoculture wetland had a similar vertical distribution of below-ground biomass over 4 years, while the mixed wetland showed a significant change in vertical distribution of below-ground biomass in the last 2 years. The monoculture wetland had a larger (P <0.05) above-ground biomass and a similar leaf biomass in the first year, and a smaller above-ground biomass (P <0.05) and a smaller leaf biomass (P <0.05) than the mixed wetland during the latter 2 years. The amount of standing dead mass was smaller in the mixed wetland than in the monoculture wetland (P <0.05). The mixed wetland exhibited a significantly lower NH4–N removal rate in the first year (P <0.05), and significantly higher NH4–N removal rate in the last year, when compared to the monoculture wetland (P <0.05). The study indicated that species competition and stubble growth resulted in significant differences between monoculture and mixed constructed wetlands in plant growth, community structure, and nutrient removal rates. [ABSTRACT FROM AUTHOR]

Differences in plant shade tolerance constitute a major mechanism driving the succession of forest communities in subtropical forests. However, the indirect effects of differences in light requirements on the growth of mid- and late-successional tree species are unclear, and this potential growth effect has not been explained at the transcriptome level. Here, a typical mid-successional dominant tree species, Schima superba Gardn. et Champ , and a typical late-successional dominant tree species, Cryptocarya concinna Hance were used as materials and planted under 100% full light (FL) and 30% FL (low light, LL) to explore the responses of tree species in different successional stages of subtropical forests to different light environments. Transcriptome sequencing was used to analyze the expression changes in genes related to growth and photoprotection under different light environments. The young leaves of S. superba accumulated more malondialdehyde (MDA) and superoxide radicals (⁠|${\mathrm{O}}_2^{{{}^{\bullet}}^{-}}$|⁠) under LL. A lower hormone content (auxin, cytokinin, gibberellin) in the young leaves, a weaker photosynthetic capacity in the mature leaves and significant downregulation of related gene expression were also found under LL, which resulted in the total biomass of S. superba under LL being lower than that under FL. The young leaves of C. concinna had less MDA and |${\mathrm{O}}_2^{{{}^{\bullet}}^{-}}$|⁠ , and a higher hormone contents under LL than those under FL. There was no significant difference in photosynthetic capacity between mature leaves in contrasting light environments. Although the biomass of C. concinna under LL was less than that under FL, the height of C. concinna under LL was higher than that under FL, indicating that C. concinna could grow well under the two light environments. Our results describing the acclimatization of light at the physiological, molecular and transcriptome levels are important for a complete understanding of successional mechanisms. [ABSTRACT FROM AUTHOR]

Photoprotection strategies that have evolved in plants to cope with high light (HL) stress provide plants with the ability to resist HL. However, it has not been clearly confirmed which photoprotection strategy is the major HL resistance mechanism. To reveal the major photoprotection mechanism against short-term high light (STHL), the physiological and biochemical responses of three Arabidopsis mutants (Col , chi and ans) under STHL were analyzed in this study. After STHL treatment, the most serious photosynthetic pigment damage was observed in chi plants. At the same time, the degrees of membrane and Rubisco damage in chi was the highest, followed by Col , and ans was the smallest. The results showed that ans with high antioxidant capacity showed higher resistance to STHL treatment than Col containing anthocyanins, while chi with no anthocyanin accumulation and small antioxidant capacity had the lowest resistance. In addition, the gene expression results showed that plants tend to synthesize anthocyanin precursor flavonoids with antioxidant capacity under STHL stress. To further determine the major mechanism of photoprotection under STHL, we also analyzed Arabidopsis lines (Col , CHS1 , CHS2 and tt4) that had the same anthocyanin content but different antioxidant capacities. It was found that CHS2 with high antioxidant capacity had higher cell viability, smaller maximal quantum yield of PSII photochemistry (F v /F m) reduction and less reactive oxygen species (ROS) accumulation under HL treatment of their mesophyll protoplasts. Therefore, the antioxidant capacity provided by antioxidant substances was the major mechanism of plant photoprotection under STHL treatment. • The antioxidant capacity was more important than light shielding effect under STHL. • Plants tend to synthesize anthocyanin precursor flavonoids with antioxidant capacity under STHL. • A higher antioxidant capacity correlated with a higher resistance index. • A higher antioxidant capacity correlated with a higher the mesophyll protoplast survival. [ABSTRACT FROM AUTHOR]

Theoretical and experimental studies have demonstrated that temperature is an important environmental factor that affects the regional distribution of plants. However, how to modify the distribution pattern of plants in different regions is a focus of current research. Obtain the information of cold tolerance genes from cold tolerance species, cloning genes with real cold tolerance effects is one of the most important ways to find the genes related to cold tolerance. In this study, we investigated whether transferring the VHA-c gene from Antarctic notothenioid fishes into Arabidopsis enhances freezing tolerance of Arabidopsis. The physiological response and molecular changes of VHA-c overexpressing pedigree and wildtype Arabidopsis were studied at −20 °C. The results showed that the malondialdehyde (MDA) and membrane leakage rates of WT plants were significantly higher than those of VHA-c8 and VHA-c11 plants, but the soluble sugar, soluble protein, proline and ATP contents of WT plants were significantly lower than those of VHA-c8 and VHA-c11 plants under −20 °C freezing treatment. The survival rate, VHA-c gene expression level and VHA-c protein contents of WT plants were significantly lower than those of VHA-c8 and VHA-c11 plants under −20 °C freezing treatment. Correlation analysis showed that ATP content was significantly negatively correlated with MDA and membrane leakage rate, and positively correlated with soluble sugar, soluble protein and proline content under −20 °C freezing treatment. These results demonstrated that overexpression of the VHA-c gene provided strong freezing tolerance to Arabidopsis by increasing the synthesis of ATP and improved the adaptability of plants in low temperature environment. • Transgenic Arabidopsis showed stronger resistance to freezing than WT. • Transgenic Arabidopsis can increase the content of ATP. • ATP content was negatively correlated with MDA and membrane leakage rate. • ATP content was positively correlated with osmoregulation substances. • VHA-c gene has potential application prospect in genetic improvement of cold tolerance. [ABSTRACT FROM AUTHOR]

Sphagneticola trilobata (L.) Pruski is one of the fast-growing malignant weeds in South China. It has severely influenced local biodiversity and native plant habitat. Photosynthesis is the material basis of plant growth and development. However, there are few reports on the photosynthetic transcriptome of S. trilobata. In this study, S. trilobata had a relatively large leaf area and biomass. The gas exchange parameters per unit area of leaves, including net photosynthetic capacity (Pn), intercellular CO2 (Ci), stomatal conductance (Gs), transpiration rate (Tr), water use efficiency (WUE), photosynthetic pigment and Rubisco protein content were higher than those of the native plant Sphagneticola calendulacea (L.) Pruski. On this basis, the differences in photosynthesis pathways between the two Sphagneticola species were analyzed by using the Illumina HiSeq platform. The sequencing results for S. trilobata and S. calendulacea revealed 159,366 and 177,069 unigenes, respectively. Functional annotation revealed 119,350 and 150,846 non-redundant protein database annotations (Nr), 96,637 and 115,711 Swiss-Prot annotations, 49,159 and 60,116 Kyoto Encyclopedia of Genes and Genomes annotations (KEGG), and 83,712 and 97,957 Gene Ontology annotations (GO) in S. trilobata and S. calendulacea, respectively. Additionally, our analysis showed that the expression of key protease genes involved in the photosynthesis pathway, particularly CP43, CP47, PsbA and PetC, had high expression levels in leaves of S. trilobata in comparison to native species. Physiological and transcriptomic analyses suggest the high expression of photosynthetic genes ensures the high photosynthetic capacity of leaves, which is one of the inherent advantages underlying the successful invasion by S. trilobata. [ABSTRACT FROM AUTHOR]

Light attenuation and antioxidation are the main mechanisms of photoprotection by anthocyanin under high light (HL) stress. Anthocyanin synthase (ANS) is the key enzyme in the downstream portion of anthocyanin synthetic pathways. To explore the role of ANS in photoprotection by anthocyanin under HL stress, homozygous ANS -deficient Arabidopsis mutants were screened from SALK_073183 and SALK_028793. Here, we obtained two deficient mutants, ans - 1 and ans - 2 , which had ANS gene expression levels equal to 5.9 and 32.9% of that of Col respectively. By analysing their physiological and biochemical responses to HL stress, we found that there were positive correlations among ANS expression level, anthocyanin content and resistance to HL. The line with the lowest ANS expression level, ans - 1 , was also the most sensitive to HL, showing the lowest anthocyanin content, chlorophyll content, F v/ F m ratio, and Rubisco content and the highest O2•− accumulation and membrane leakage rate, although it also had the highest antioxidant capacity. Experimental evidence suggests that ANS mainly regulated the light-attenuating function of anthocyanin in photoprotection under HL. Blocking excess light is an important function of anthocyanin that protects plants from HL stress, and a high antioxidant capacity cannot compensate for the absence of the light-shielding function of anthocyanin. Upon high light stress, light-shielding and antioxidation are the main mechanisms of photoprotection by anthocyanin, the final key enzyme in whose synthetic pathways is anthocyanin synthase (ANS). This investigation tackled the role of ANS in photoprotection: ANS mainly regulates the light-shielding of anthocyanin in photoprotection. Additionally, we found that light-shielding is the important function in photoprotection of anthocyanins, and high antioxidant capacity cannot compensate for the absence of the light-shielding. [ABSTRACT FROM AUTHOR]

Previous studies have suggested that high light (HL) stress causes photoinhibition in plants, while anthocyanins could protect the photosynthetic apparatus against photoinhibition. However, the photoprotection mechanism of anthocyanins is still ambiguous. We studied physiological responses and molecular changes for CHS -overexpression lines ( CHS1 , CHS2 , CHS3 ), Arabidopsis thaliana ecotype Columbia ( Col ), and T-DNA insertion lines of CHS ( tt4 ) under HL (200 μmol m −2  s −1 ) to explore the photoprotection mechanism of anthocyanins. The results showed that HL induced anthocyanin synthesis and accumulation. The leaves of CHS -overexpression lines turned reddest and the genes, including CHS, DFR, ANS, were expressed at highest levels. Thus, the CHS -overexpression lines maintained the highest photosynthetic capacity and suffered the least damage from HL of the three phenotypes. However, the CHS enzyme and anthocyanins were undetectable in tt4 during the experiment. Correspondingly, chlorophyll fluorescence parameters of tt4 declined greatly. The photosynthetic apparatus and cell membranes were also impaired dramatically. The physiological characteristics of Col were compared between CHS -overexpression lines and tt4 . Together, the results suggest that over-expression of CHS gene enhances HL resistance by synthesizing more anthocyanins, that anthocyanins enhance the adaptability of plants to HL and that they maintain photosynthetic capacity via both antioxidation and attenuation of light. [ABSTRACT FROM AUTHOR]

The successful development of photosynthetic organs is the basis of plant growth and community development. To reveal photo-acclimation to high irradiance in tree species during the course of leaf development and plant succession of subtropical forests, photosynthetic efficiency and photoprotective compounds were analyzed in young and mature leaves of three mid-successional tree species ( Castanopsis fissa , Castanopsis chinensis and Schima superba ) and three late-successional tree species ( Machilus chinensis , Cryptocarya chinensis and Cryptocarya concinna ), grown in 100% full sunlight (FL) or 30% of FL (low light, LL). Young leaves of the two species groups exhibited lower chlorophyll (Chl) content, Rubisco content, net photosynthetic rate ( P n ), carboxylation efficiency ( CE ), effective photochemical yield ( Φ PSII ), photorespiratory electron flow ( J O ), but higher dark respiration ( R d ), and ratios of carotenoids/chlorophylls (Car/Chl), anthocyanins/chlorophylls (Anth/Chl), flavonoids/chlorophylls (Flav/Chl), phenols/chlorophylls (Phen/Chl) and total antioxidant capacity/chlorophylls (TAC/Chl) than those of mature leaves, regardless of growth irradiance. Young leaves of both species groups demonstrated a higher flexibility of Anth/Chl, Flav/Chl, Phen/Chl and TAC/Chl in response to different light conditions than mature leaves. Flav/Chl in young leaves of late-successional group was remarkably higher than that of mid-successional group under the same light conditions. There was a negative correlation between antioxidant-dependent photoprotective potential and photosynthetic efficiency in young and mature leaves of the six tree species grown under either FL or LL. Our results explain partial mechanisms that lie behind the replacement of communities in subtropical forests: highly integrated photoprotective potential allows young leaves of shade-tolerant late-successional species to develop smoothly into mature organs under high irradiance. [ABSTRACT FROM AUTHOR]

The abundance of phenolic compounds (including anthocyanins) in leaves is associated with photosynthetic performance, but the regulatory mechanism is unclear. Schima superba Gardn. et Champ. and Cryptocarya concinna Hance. which exhibit distinct anthocyanin accumulation patterns, are dominant tree species in the early- and late-successional stages, respectively, of subtropical forests in China. RNA-seq and analyses of phenolic concentrations, antioxidant capacity and photosynthetic characteristics were performed on young and mature leaves of these two species under contrasting light conditions. The high-light-acclimated young leaves of S. superba and C. concinna and low-light-acclimated young leaves of C. concinna were red. These red leaves had higher ratios of electron transport rate to gross photosynthesis (ETR: P gross) and total antioxidant capacity to chlorophyll (TAC:Chl) than did the green leaves, regardless of light conditions. In addition, the red leaves had a higher expression level of the UDP-glucose:flavonoid 3-O-glucosyltransferase (UFGT) gene than did the green leaves, irrespective of light conditions. Total antioxidant capacity was positively correlated with flavonoid content in C. concinna leaves and with total phenolic content in leaves of both species under both high and low light. Consistent with the measurements of photosynthetic performance and flavonoids:Chl ratio, photosynthesis-related genes were extensively downregulated and flavonoid-pathway-related genes were extensively upregulated in young leaves relative to mature leaves. Under high and low light, both non-photochemical quenching and TAC:Chl, which serve as different types of photoprotective tools, were enhanced in young leaves of S. superba, whereas only TAC:Chl was enhanced in young leaves of C. concinna. Our results indicate that the biosynthesis of phenolic compounds in young leaves is likely enhanced by an imbalance between photosynthetic electron supply and demand and that flavonoids play a larger role in meditating photoprotection in late-successional species than in early-successional ones. [ABSTRACT FROM AUTHOR]

Differences in response patterns to spatio-temporal changes in environmental stressors mediated by seasonal climatic differences reflect the underlying adaptation strategies of plants, and can provide key information on how tree species respond to seasonal climatic changes at different successional stages. However, in forests dominated by subtropical broadleaf evergreen species, the relationship between leaf photoprotection strategies and their construction cost strategies in different seasons remains unclear. It limits the assessment of the impact of seasonal climate change on community growth and exploration of potential drivers of community succession. In this study, we measured photoprotective substances, chlorophyll fluorescence, photosynthetic pigments and leaf construction cost (CC) in leaves of three mid-successional and three late-successional tree species in a subtropical broadleaf evergreen forest in different seasons. Our data showed that the young leaves of mid-successional trees had higher photoprotection ability in summer compared to winter, and were therefore better adapted to high temperature and high light conditions in summer, but not to low temperature and high light conditions in winter. The young leaves of late-successional trees had strong and flexible photoprotection in both summer and winter, which ensured normal growth of the young leaves under high temperature and high light in summer, and under low temperature and high light in winter. In addition, the photoprotection of the leaves was positively correlated with CC, suggesting that an increase in photoprotective capacity of plants was accompanied by an increase in its investment in CC. This was a response of the plants to environmental stress and the sacrifices it needed to make to maintain its survival. The differential growth patterns of late-successional species, which could grow normally in summer and winter, and mid-successional species, which were adapted to grow in summer but not in winter, may be key clues to the gradual replacement of mid-successional species by late-successional species. • Mid-successional tree species photoprotective potential may decrease in winter. • Late-successional tree species photoprotective potential may increase in winter. • Mid- and late-successional tree species have different CC in summer and winter. • Increased photoprotection capacity of leaves is accompanied by an increase in CC. • Mid and late-successional species have different growth patterns in summer and winter. [ABSTRACT FROM AUTHOR]

To reveal effects of elevated atmospheric CO2 on tolerance to the herbicide glyphosate in the populations of goosegrass (Eleusine indica) known to have resistance to this herbicide, two biotypes of goosegrass, a resistant (R) and a susceptible (S) biotype, were analyzed after exposed to ambient (400 μmol mol-1) and elevated CO2 (800 μmol mol-1) for 25 d. The results showed that elevated CO2 had little effect on growth of both biotypes. At elevated CO2, shoot biomass of R biotype was statistically lower than of S biotype (P<0.5). The dose-response analysis showed that glyphosate tolerance was reduced by 60% in R biotype exposed to elevated Co2 while it was slightly increased in S biotype. Elevated Co2 also had more adverse effects on photosynthetic capacity of R biotype than S biotype. As a result, maximum rate of net photosynthesis (Amax) and carboxylation efficiency (CE) under elevated CO2 in R biotype were significantly lower than in S biotype (P<0.5). These results indicate that elevated atmospheric Co2 can lead to a compromise in glyphosate tolerance of R biotype associated with poor photosynthetic characteristics, and thus will affect weed management involved with herbicide resistance in prospective agricultural systems. © 2015 Friends Science Publishers [ABSTRACT FROM AUTHOR]

In order to reveal the mechanism of succession in subtropical forest along a light gradient, we investigated photosynthetic physiological responses to three light environments in five tree species including a pioneer species Pinus massoniana Lamb., two mid-successional species Schima superba Gardn. et Champ. and Castanopsis fissa (Champ. ex Benth.) Rehd. et Wils., and two late-successional species Cryptocarya concinna Hance. and Acmena acuminatissima (BI.) Merr et Perry) that were selected from Dinghu Mountain subtropical forest, South China. Results showed that,amongthe three kinds of species in all light conditions (100%,30%and 12% of full sunlight), the pioneer species had the highest photosynthetic capacity (Amax), light saturation point (LSP), carboxylation efficiency (CE) and maximum utilisation rate of triose phosphate (TPU) that characterised a strong photosynthetic capacity and high carbon dioxide uptake efficiency. However, a higher light compensation point (LCP) and dark respiration (Rd) as well as lower apparent quantum yield (AQY) indicated that the pioneer specie cannot adapt to low light conditions. Mid-successional species had photosynthetic characteristics in between pioneer and late-successional species, but had the greatest effective quantum yield of PSII (ΦPSII) and light use efficiency (LUE, expressed in terms of photosynthesis). In contrast to pioneer and mid-successional species, late-successional species had lower photosynthetic capacity and carbon uptake efficiency, but higher shade tolerance and high-light heat dissipation capacity, as characterised by higher levels of total xanthophylls cycle pigments (VAZ) and de-epoxidation state of xanthophyll cycle (DEPs). These results indicate that photosynthetic capacity decreases along the successional axis and that late-successional species have more responsive heat dissipation capability to compensate for their inferior photosynthetic capacity. [ABSTRACT FROM AUTHOR]

Chlorophyll fluorescence and antioxidative capability in detached leaves of the wild type Arabidopsis thaliana L. ecotype Landsberg erecta ( Ler) and three mutants deficient in anthocyanins biosynthesis ( tt3, tt4, and tt3tt4) were investigated during treatment with temperatures ranging 25–45 °C. In comparison with the wild type, chlorophyll fluorescence parameters Fv/Fm, ΦPSII, electron transport rate (ETR), Fv/Fo and qP in three anthocyanin-deficient mutants showed a more rapidly decreasing rate when the temperature was over 35 °C. Non-photochemical quenching (NPQ) in these mutants was almost completely lost at 44 °C, whereas the content of heat stable protein dropped and the rate of the membrane leakage increased. Fo-temperature curves were obtained by monitoring Fo levels with gradually elevated temperatures from 22 °C to 72 °C at 0.5 °C/min. The inflexion temperatures of Fo were 45.8 °C in Ler, 45.1 °C in tt3, 44.1 °C in tt4 and 42.3 °C in tt3tt4, respectively. The temperatures of maximal Fo in three mutants were 1.9–3.8 °C lower than the wild type plants. Meanwhile, three mutants had lower activities of superoxide dismutase (SOD) and ascorbate peroxidase (APX) and an inferior scavenging capability to DPPH (1.1-diphenyl-2-picrylhy.drazyl) radical under heat stress, and in particular tt3tt4 had the lowest antioxidative potential. The results of the diaminobenzidine-H2O2 histochemical staining showed that H2O2 was accumulated in the leaf vein and mesophyll cells of mutants under treatment at 40 °C, and it was significantly presented in leaf cells of tt3tt4. The sensitivity of Arabidopsis anthocyanins-deficient mutants to high temperatures has revealed that anthocyanins in normal plants might provide protection from high temperature injury, by enhancing its antioxidative capability under high temperature stress. [ABSTRACT FROM AUTHOR]

• Different photoprotection strategies for mid- and late-successional tree species. • Mid- and late-successional tree species response patterns to high-light were different. • The mid-successional tree species better tolerate high-light. • Late-successional tree species has greater restoration ability after high-light stress. Light adaptability is a major driver of succession and evolution in natural forest plant communities. However, the relationship between plants and light is contradictory; light provides energy for plant growth, but excessive light negatively affects plant growth. To reveal the pattern of plant adaptation to diurnal variation in light, photoprotection strategies were analyzed in young and mature leaves of six dominant species at two successional stages. Mature leaves of both mid- and late-successional dominant species exhibited a higher net photosynthetic rate (Pn) than young leaves. In particular, the mature leaves of the mid-successional tree species had higher high-light tolerance because of a higher Pn, water use efficiency (WUE) and electron transfer rate (ETR). In contrast, the mature leaves of the late-successional tree species had a higher restoration ability after high-light stress because of higher thermal energy dissipation and faster stomatal regulation. Young leaves of both the mid- and late-successional dominant species exhibited a higher photoprotection capability than mature leaves. The young leaves of the mid-successional tree species had higher high-light tolerance because of their highest WUE and anthocyanin/chlorophyll (Anth/Chl) and higher flavonoid/chlorophyll (Flav/Chl), total phenolics/chlorophyll (Phen/Chl) and total antioxidant capacity/chlorophyll (TAC/Chl) ratios. The young leaves of the late-successional tree species had a stronger restoration ability due to highest Flav/Chl, Phen/Chl, and TAC/Chl ratios and a higher moisture content and non-photochemical quenching coefficient (qN, NPQ). This study shows that in a high-light environment, when leaves are at the same developmental stage, mid-successional tree species better tolerate high-light, while late-successional tree species have a greater restoration ability after high-light stress. [ABSTRACT FROM AUTHOR]

The leaves of many plants are red during particular stages of their lives, but the adaptive significance of leaf colouration is not yet clearly understood. In order to reveal whether anthocyanins play a similar role (i.e. antioxidants) in different seasonal contexts, this study investigated species with red young leaves in the subtropical forest of Dinghushan biosphere reserve (South China) during summer and winter and compared group leaf characteristics between the two seasons. Of 62 total species, 33 exhibited red young leaves in summer only, 6 in winter only, and 23 in both seasons. The anthocyanins extracted from most of these species had an absorption peak at ~530 nm. Frequency distribution analysis showed that the species containing anthocyanins at levels ranging from 0.02 to 0.04 μmol cm−2 occurred most frequently in summer or winter. Based on conditional grouping of the species, no significant variation was observed in the average anthocyanin contents and antioxidant abilities between summer and winter; the flavonoid content in summer was 2-fold that in winter, whereas the anthocyanin:flavonoid ratio in summer was only half that in winter. Moreover, a positive correlation between anthocyanins and flavonoids was found in summer. Therefore, it is less likely for anthocyanins to serve as antioxidants in summer than winter, because such a function in summer leaves is readily replaced by other flavonoids. [ABSTRACT FROM AUTHOR]

Several auxin herbicides, such as 2, 4-D and dicamba, have been used to eradicate an exotic invasive weed Ipomoea cairica in subtropical China, but restraining the re-explosion of this weed is still a challenge. Since ethylene is one of the major intermediate functioning products during the eradication process, we explored the possibility, mechanism and efficiency of using ethephon which can release ethylene to control Ipomoea cairica. The results of the pot experiment showed that 7.2 g /L ethephon could totally kill Ipomoea cairica including the stems and roots. The water culture experiment indicated that ethephon released an abundance of ethylene directly in leaves and caused increases in electrolyte leakage, 1-aminocyclopropane-1-carboxylic acid (ACC), abscisic acid (ABA) and H2O2 and decreases in chlorophyll content and photosynthetic activity, finally leading to the death of Ipomoea cairica. The field experiment showed that the theoretical effective concentration of ethephon for controlling Ipomoea cairica (weed control efficacy, WCE = 98%) was 4.06 g/L and the half inhibitory concentration (I50) was 0.56 g/L. More than 50% of the accompanying species were insensitive to the phytotoxicity of ethephon. Therefore, ethephon is an excellent alternative herbicide for controlling Ipomoea cairica. [ABSTRACT FROM AUTHOR]