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Elevated atmospheric CO 2 and nitrogen are major environmental factors affecting shoot growth. The objectives of this study are to determine the interactive effects of elevated CO 2 and nitrogen on leaf growth in tall fescue ( Festuca arundinacea) and to identify major proteins and associated metabolic pathways underlying CO 2 -regulation of leaf growth under insufficient and sufficient nitrate conditions using proteomic analysis. Plants of tall fescue treated with low nitrate level (0.25 mM, LN), moderate nitrate level (4 mM, MN) and high nitrate level (32 mM, HN) were exposed to ambient (400 μmol mol -1 ) and elevated (800 μmol mol -1 ) CO 2 concentrations in environment-controlled growth chambers. Increased atmospheric CO 2 concentration increased leaf length and shoot biomass, which corresponded to increased content of indo-acetic acid, gibberellic acid, cytokinins and reduced content of abscisic acid under sufficient nitrate conditions (MN and HN conditions). Low nitrate supply limited shoot growth and hormonal responses to elevated CO 2 . Proteomic analysis of plants exposed to elevated CO 2 under LN and MN conditions demonstrated the increases in the abundance of many proteins due to elevated CO 2 under MN condition involved with cell cycle and proliferation, transcription and translation, photosynthesis (ribosomal and chlorophyll a/b-binding proteins), amino acids synthesis, sucrose and starch metabolism, as well as ABA signaling pathways (ABA-induced proteins). Our results revealed major proteins and associated metabolic pathways associated with the interactive effects of elevated CO 2 and nitrate regulating leaf growth in a perennial grass species.

One-month-old lettuce seedlings were planted in the field with and without prior hairy vetch (Vicia villosa L.) incorporation (HV and Fallow, respectively). The periods between hairy vetch incorporation and lettuce planting were 1 day, 8 days and 15 days. The inorganic nitrogen concentration in the soil was higher after hairy vetch incorporation, as well as the nitrogen concentration in the lettuce leaves from the HV plot compared to the Fallow plot, at any planting period. When lettuce seedlings were planted 8 days after hairy vetch incorporation, the leaf dry weight in the HV plots was 11% lower than that in the Fallow plots 4 days after planting; however, leaf growth recovered and the dry weight was 24% higher 12 days after planting, which could be due to enhanced leaf growth as the result of additional accumulated nitrogen provided by the hairy vetch. In the incubation experiment, it was suggested that the inhibitory effect of hairy vetch decomposition was not due to allelopathic substances. Therefore, in the hairy-vetch-incorporated field, growth suppression in the lettuce plants occurred early and continued for a short period after hairy vetch incorporation, but the damage due to the growth suppression effect was minor. More importantly, nitrogen supplied from the hairy vetch promoted lettuce growth after the inhibition period. [ABSTRACT FROM AUTHOR]

In this paper, hyperspectral imaging technology, combined with chemometrics methods, was used to detect the nitrogen content of soybean leaves, and to achieve the rapid, non-destructive and in situ detection of the nitrogen content in soybean leaves. Soybean leaves under different fertilization treatments were used as the research object, and the hyperspectral imaging data and the corresponding nitrogen content data of soybean leaves at different growth stages were obtained. Seven spectral preprocessing methods, such as Savitzky–Golay smoothing (SG), first derivative (1-Der), and direct orthogonal signal correction (DOSC), were used to establish the quantitative prediction models for soybean leaf nitrogen content, and the quantitative prediction models of different spectral preprocessing methods for soybean leaf nitrogen content were analyzed and compared. On this basis, successive projections algorithm (SPA), genetic algorithm (GA) and random frog (RF) were employed to select the characteristic wavelengths and compress the spectral data. The results showed the following: (1) The full-spectrum prediction model of soybean leaf nitrogen content based on DOSC pretreatment was the best. (2) The PLS model of soybean leaf nitrogen content based on the five characteristic wavelengths had the best prediction performance. (3) The spatial distribution map of soybean leaf nitrogen content was generated in a pixel manner using the extracted five characteristic wavelengths and the DOSC-RF-PLS model. The nitrogen content level of soybean leaves can be quantified in a simple way; this provides a foundation for rapid in situ non-destructive detection and the spatial distribution difference detection of soybean leaf nitrogen. (4) The overall results illustrated that hyperspectral imaging technology was a powerful tool for the spatial prediction of the nitrogen content in soybean leaves, which provided a new method for the spatial distribution of the soybean nutrient status and the dynamic monitoring of the growth status. [ABSTRACT FROM AUTHOR]

Determining the effects of organic fertilizer and foliar application of mallow leaf extract on the growth and yield of eggplant was the aim of this latest study held in spring 2021 in the Al-Najaf Province, Iraq. The treatments comprising adding decomposed palm waste to the soil at three levels (0, 16, and 32 mg ha-1), foliar application of mallow leaf extract at three concentrations (0, 0.2, and 0.4 gm.l-1), and their interactions incurred probing in eggplants. The experiment began in a randomized complete blocks design (RCBD) with factorial arrangement and three replications. The results obtained through the analysis of variance continued to further evaluation through the least significant difference test to compare and separate the various means. The results showed that organic fertilization with decomposing palm residues at 32 mg ha-1 significantly outperformed the other treatments for plant height, total leaves, dry weight of vegetative growth, fruits per plant, yield per plant, total yield, nitrogen (%), and total chlorophyll content in the leaves. [ABSTRACT FROM AUTHOR]

In this study, we are identifying differences in the UV/VIS/NIR (ultraviolet/visible/near-infrared) spectral signatures of maize leaves according to a range of fertilization rates from 0 to 240 kg/ha. By utilizing a FieldSpec spectrometer, it was determined that the spectral response displayed significant differences (p-value = 0.05) under the influence of nitrogen fertilization within the following ranges: near ultraviolet: 355 nm (±5 nm), visible light (green): 550 nm (±15 nm, wide band); 555 nm (±5 nm, narrow band), red edge: 720 nm (±20 nm), infrared: 1075 nm (±50 nm); 1380 nm (±20 nm). Based on the estimated differences, two remote sensing indicators for maize during the 5–6 leaf growth stage and nitrogen fertilization were developed: (NIR-RED_EDGE)/(NIR+RED_EDGE) and (NIR-GREEN)/(NIR+GREEN) where NIR is 1075 nm band, RED_EDGE is 720 nm band and GREEN is 550 nm band. These indicators determined the level of fertilization with a coefficient of determination R2 value greater than 0.85. [ABSTRACT FROM AUTHOR]

In this study, leaf nutrient contents, resorption efficiency (RE) and resorption proficiency (RP) values were examined in three sympatric woody species—P. tremula, Q. maranthera subsp. syspirensis and L. caucasica subsp. orientalis during two years in Northern Black Sea Region (Turkiye). According to the data obtained the highest N, P, K, Mg, Ca, Fe and Cu concentrations in green leaves were found in L. caucasica in both two years. However, the highest Zn concentrations in green leaves were found in P. tremula whereas the highest Mn concentrations were found in Q. macranthera. PRE was found to be higher than NRE and for all other elements in the study area. On the other hand, all studied species demonstrated similar RE values for macronutrients in general. Negative RE values were found with respect to Cu, Fe, Ca and MnRE in P. tremula, and with respect to CaRE in L. caucasica. However, all elements were resorbed in Q. macranthera. Our data indicate that species specificity plays an important role in resorption of microelements in the studied species. P. tremula and Q. macranthera were N and P-proficient only in first year whereas L. caucasica was not N and P-proficient in the present study. Nitrogen and phosphorus limitations varied due to plant species and leaf growth stages with respect to N/P ratios in the study area. [ABSTRACT FROM AUTHOR]

Triose phosphate utilization (TPU) is a biochemical process indicating carbon sink–source (im)balance within leaves. When TPU limits leaf photosynthesis, photorespiration-associated amino acid exports probably provide an additional carbon outlet and increase leaf CO2 uptake. However, whether TPU is modulated by whole-plant sink–source relations and nitrogen (N) budgets remains unclear. We address this question by model analyses of gas-exchange data measured on leaves at three growth stages of rice plants grown at two N levels. Sink–source ratio was manipulated by panicle pruning, by using yellower-leaf variant genotypes, and by measuring photosynthesis on adaxial and abaxial leaf sides. Across all these treatments, higher leaf N content resulted in the occurrence of TPU limitation at lower intercellular CO2 concentrations. Photorespiration-associated amino acid export was greater in high-N leaves, but was smaller in yellower-leaf genotypes, panicle-pruned plants, and for abaxial measurement. The feedback inhibition of panicle pruning on rates of TPU was not always observed, presumably because panicle pruning blocked N remobilization from leaves to grains and the increased leaf N content masked feedback inhibition. The leaf-level TPU limitation was thus modulated by whole-plant sink–source relations and N budgets during rice grain filling, suggesting a close link between within-leaf and whole-plant sink limitations. [ABSTRACT FROM AUTHOR]

Nitrogen (N) is an essential macronutrient for plants, and its remobilization is key for adaptation to deficiency stress. However, there is limited understanding of the regulatory mechanisms of N remobilization in the important crop species Brassica napus (oilseed rape). Here, we report the identification of a transcription factor, BnaA9.WRKY47 , that is induced by N starvation in a canola variety. At the seedling stage, BnaA9.WRKY47 -overexpressing (OE) lines displayed earlier senescence of older leaves and preferential growth of juvenile leaves compared to the wild type under N starvation. At the field scale, the seed yield was significantly increased in the BnaA9.WRKY47 -OE lines compared with the wild type when grown under N deficiency conditions and, conversely, it was reduced in BnaA9.WRKY47 -knockout mutants. Biochemical analyses demonstrated that BnaA9.WRKY47 directly activates BnaC7.SGR1 to accelerate senescence of older leaves. In line with leaf senescence, the concentration of amino acids in the older leaves of the OE lines was elevated, and the proportion of plant N that they contained was reduced. This was associated with BnaA9.WRKY47 activating the amino acid permease BnaA9.AAP1 and the nitrate transporter BnaA2.NRT1.7. Thus, the expression of BnaA9.WRKY47 efficiently facilitated N remobilization from older to younger leaves or to seeds. Taken together, our results demonstrate that BnaA9.WRKY47 up-regulates the expression of BnaC7.SGR1 , BnaA2.NRT1.7 , and BnaA9AAP1 , thus promoting the remobilization of N in B. napus under starvation conditions. [ABSTRACT FROM AUTHOR]

The nutrient filter function is an important ecosystem service of seagrass meadows that mitigates the consequences of coastal eutrophication. In northeast Hainan in China, large seagrass areas were lost due to chronic eutrophication induced by untreated pond aquaculture effluents. However, in adjacent areas, seagrasses could survive due to seasonal exposure (i.e., not chronic) to eutrophication only. In a way, the conditions in these areas represent a transitional environment which allows investigating the effect of eutrophication on seagrass performance and their nitrogen uptake capacity. We tested how a 4‐week in situ nutrient enrichment affected inorganic nitrogen uptake rates of a multispecies seagrass meadow in eutrophic and non‐eutrophic seasons, in light and in darkness. All species maintained nitrogen uptake in the dark and preferred ammonium over nitrate. In the eutrophic season, the seagrass leaf biomass and growth were lower resulting in a lower nitrogen filter capacity. Among the species present, Cymodocea rotundata and Cymodocea serrulata covered 48% and 45%, respectively, of their daily nitrogen demand for leaf growth through leaf uptake from the water column, while it was only 30% for Thalassia hemprichii, the last remaining species in meadows degraded by eutrophication, as deduced from previous studies. It indicates that a multispecies seagrass meadow has a higher nitrogen filter capacity than a monospecific T. hemprichii meadow. By reducing seagrass diversity and, hence, the nitrogen filter function, eutrophication triggers a self‐reinforcing process. Once the nitrogen filtering capacity of a seagrass meadow is exhausted, further eutrophication and seagrass loss are expected. [ABSTRACT FROM AUTHOR]

In order to investigate the possibility of improvement of yield, yield components and the concentration of some nutrients in rice leaves (Tarom variety) by using rice straw and its biochar, a factorial experiment was conducted in the form of a randomized complete block design in nine treatments and three replications in the farm of Sari Agricultural Sciences and Natural Resources University, Sari, north of Iran, in 2021. The first factor was rice straw (S) at three levels of zero, 2 and 4 tons/ha and the second factor was rice straw biochar (B) at three levels of zero, 1 and 2 tons/ha. The maximum concentration of potassium (1.22%), nitrogen (4.73%) and iron (208 mg/kg) in the flag leaf was observed when rice was grown in the high levels of rice straw and particularly its biochar. Also, the concentration of silicon, manganese and zinc in the flag leaf increased with the increase in the levels of rice straw and its biochar. By increasing the use of rice straw and its biochar, the number of tillers, plant height, panicle length, weight of 1000 seeds and the number of filled seeds increased significantly. The combined use of rice straw and its biochar increased the rice grain yield, indicating a 1.78 times increase in the treatment of 2 tons/ha of rice straw biochar + 4 tons/ha of rice straw (S2B2) compared to the control. Therefore, it can be concluded that the application of 2 tons/ha of biochar and 4 tons/ha of rice straw can lead to the maximum grain yield by increasing the concentration of nutrients in the flag leaf and improving the growth and yield components of rice. [ABSTRACT FROM AUTHOR]

Salt stress is a major adverse environmental factor limiting plant growth. Nitrogen (N) application is an effective strategy to alleviate the negative effects of salt stress on plants. To improve the knowledge of the mechanism of N application on alleviating salt stress on rapeseed seedlings, a pot experiment was conducted with four N application treatments (0, 0.1, 0.2, and 0.3 g N kg-1 soil, referred to as N0, N1, N2, and N3, respectively) and exposed to non-salt stress (0 g NaCl kg-1 soil, referred to as S0) and salt stress (3 g NaCl kg-1 soil, referred to as S1) conditions. The results indicated that in comparison with non-salt stress, salt stress increased the Na content (236.53%) and reactive oxygen species (ROS) production such as hydrogen peroxide (H2O2) (30.26%), resulting in cell membrane lipid peroxidation characterized by an increased content of malondialdehyde (MDA) (122.32%) and suppressed photosynthetic rate (15.59%), finally leading to inhibited plant growth such as shorter plant height, thinner root neck, lower leaf area, and decreased dry weight. N application improved the plant growth, and the improvement by N application under salt stress was stronger than that under non-salt stress, suggesting that rapeseed seedlings exposed to salt stress are more sensitive to N application and require N to support their growth. Moreover, seedlings exposed to salt stress under N application showed lower ROS accumulation; increased photosynthesis; higher antioxidants such as catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), and ascorbic acid (AsA); and greater accumulation of osmotic substances including soluble protein, soluble sugar, and proline, as compared with seedlings without N application. In particular, the best improvement by N application under salt stress occurred at the N2 level, while too high N application could weaken the improvement due to inhibited N metabolism. In summary, this study suggests that moderate N application can improve photosynthesis, antioxidants, and osmoregulation to alleviate the adverse effects of salt stress in rapeseed seedlings. [ABSTRACT FROM AUTHOR]

Coffee (Coffea arabica L.) plants have been assorted as highly suitable to growth at elevated [CO2] (eCa), although such suitability is hypothesized to decrease under severe shade. We herein examined how the combination of eCa and contrasting irradiance affects growth and photosynthetic performance. Coffee plants were grown in open-top chambers under relatively high light (HL) or low light (LL) (9 or 1 mol photons m−2 day−1, respectively), and aCa or eCa (437 or 705 μmol mol–1, respectively). Most traits were affected by light and CO2, and by their interaction. Relative to aCa, our main findings were (i) a greater stomatal conductance (gs) (only at HL) with decreased diffusive limitations to photosynthesis, (ii) greater gs during HL-to-LL transitions, whereas gs was unresponsive to the LL-to-HL transitions irrespective of [CO2], (iii) greater leaf nitrogen pools (only at HL) and higher photosynthetic nitrogen-use efficiency irrespective of light, (iv) lack of photosynthetic acclimation, and (v) greater biomass partitioning to roots and earlier branching. In summary, eCa improved plant growth and photosynthetic performance. Our novel and timely findings suggest that coffee plants are highly suited for a changing climate characterized by a progressive elevation of [CO2], especially if the light is nonlimiting. [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]

SUMMARY: Ammonium (NH4+)‐based fertilization efficiently mitigates the adverse effects of nitrogen fertilization on the environment. However, high concentrations of soil NH4+ provoke growth inhibition, partly caused by the reduction of cell enlargement and associated with modifications of cell composition, such as an increase of sugars and a decrease in organic acids. Cell expansion depends largely on the osmotic‐driven enlargement of the vacuole. However, the involvement of subcellular compartmentation in the adaptation of plants to ammonium nutrition has received little attention, until now. To investigate this, tomato (Solanum lycopersicum) plants were cultivated under nitrate and ammonium nutrition and the fourth leaf was harvested at seven developmental stages. The vacuolar expansion was monitored and metabolites and inorganic ion contents, together with intracellular pH, were determined. A data‐constrained model was constructed to estimate subcellular concentrations of major metabolites and ions. It was first validated at the three latter developmental stages by comparison with subcellular concentrations obtained experimentally using non‐aqueous fractionation. Then, the model was used to estimate the subcellular concentrations at the seven developmental stages and the net vacuolar uptake of solutes along the developmental series. Our results showed ammonium nutrition provokes an acidification of the vacuole and a reduction in the flux of solutes into the vacuoles. Overall, analysis of the subcellular compartmentation reveals a mechanism behind leaf growth inhibition under ammonium stress linked to the higher energy cost of vacuole expansion, as a result of alterations in pH, the inhibition of glycolysis routes and the depletion of organic acids. Significance Statement: Ammonium nutrition provoked tomato growth inhibition, partly caused by the reduction of cell enlargement. Combining in vivo pH measurement, non‐aqueous fractionation and mathematical modeling, we report that the decrease in vacuolar pH and organic acid concentrations incurred an increase in the energy cost of solute accumulation in the vacuole, and thus limited cell growth under ammonium nutrition. [ABSTRACT FROM AUTHOR]

During Populus euphratica ontogeny, the morphological changes of stems and leaves, nutrient and endogenous hormone contents were significantly different, but the relationship between these changes and the number of flower buds was not clear. We counted the number of P. euphratica flower buds, and measured the morphological of the stems and leaves nutrient and endogenous hormone contents at different ontogeny to clarify the change trends in the morphology and nutrient and endogenous hormone contents of stems and leaves and mutual relationships in the flower bud number throughout the ontogeny. The results showed that in diameter 4, flower buds and broad-ovate leaves appeared meanwhile, indicating that P. euphratica had entered the reproductive growth stage. Between diameter 4 to 12, stem length, leaf number and leaf C/N gradually decreased, and leaf area, leaf nitrogen, organic carbon, and ZR contents gradually increased, indicating diameters 4-12 represent the stage during which vegetative growth and reproductive growth cooccur in P. euphratica. In diameter 14, flower bud number increased significantly, while leaf shape index and stem diameter decreased. P. euphratica began to enter the vigorous reproductive growth stage. In addition, correlations were found between leaf and stem nitrogen, phosphorus, organic carbon, GA3, ABA, IAA contents, leaf C/N and leave and stem morphology was closely related to the ontogeny; the change in coordination significantly affected the flower bud number. The synergistic changes in the nutrient and endogenous hormone contents in P. euphratica stems and leaves regulate the morphology of stems and leaves and flower bud number and directly or indirectly affect the transition from vegetative growth to reproductive growth. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Henan Agricultural Sciences is the property of Editorial Board of Journal of Henan Agricultural Sciences 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.)

Annual rotations of paddy rice with upland crops has become more popular in recent years under the increasing pressure to ensure food security. Five representative paddy-upland rotations (PURs), i.e., garlic-rice (GR), wheat-rice (WR), broad bean-rice (BR), rapeseed-rice (RR), and potato-rice (PR) under two nitrogen (N) treatments were assessed from 2014 to 2017 to investigate the effects of PURs on paddy productivity and the regulatory effects of N fertilizer. Results showed that different PURs influenced the growth of tillers and leaves in the vegetative growth stage, leading to differences in effective tiller number, heading-stage canopy structure, and dry matter accumulation, resulting in significant differences in rice yield. With N application (NA), rice yields of GR and PR with straw mulching were higher than those of RR and WR rotations. Without N application (CK), rice yield in PR was only lower than that in the BR rotation. Compared with the other four PURs, rice yields under WR were the lowest, with decreases of 3.7% and 12.5% under NA and CK conditions, respectively. In conclusion, preceding crop and N application significantly affect paddy productivity by influencing rice vegetative growth. The WR rotation does not seem conducive to sustainable paddy productivity under traditional cultivation methods, whereas, the PR cropping system shows potential for sustainable crop production. Particular attention should be paid to upland crop selection and crop management practice, especially regarding C and N inputs, to ensure ssustainable production of paddy rice. [ABSTRACT FROM AUTHOR]

The effect of nitrogen (N) nutrition on grapevine carbon (C) dynamics has been well studied at the annual scale, but poorly addressed at a pluriannual timescale. The aim of this study was to quantify, in an integrated conceptual framework, the effect of N nutrition on potted grapevine growth and storage over 2 consecutive years. The consequences of using destructive measurements were investigated using a hierarchical Bayesian model. The rate and duration of leaf growth were both positively impacted by the chlorophyll content of the leaves, but they were negatively impacted by the initial carbohydrate measurements, raising a distortion in the estimation of initial reserves. The C production per unit of global radiation depended on the leaf area dynamics. The allocation of dry matter mainly relied on the phenological stage. The present study highlights the importance of using appropriate statistical methods to overcome uncertainties due to destructive measurements. The genericity of the statistical approach presented may encourage its implementation in other agronomy studies. Based on our results, a simple conceptual framework of grapevine pluriannual growth under various N supplies was built. This provides a relevant basis for a future model of C and N balance and responses to N fertilization in grapevine. [ABSTRACT FROM AUTHOR]

A quantitative estimation of nitrogen content in rice leaves has been one of the most critical steps to realize precision fertilization and variety breeding in modern agriculture. Optical remote sensing technology has been emerging in recent years. The multi- and hyper-spectral remote sensing data can be utilized to rapidly obtain the physical and chemical parameters, such as the rice nutritional status, pest stress, and phenotypic information. Therefore, it is very necessary to implement the high-throughput acquisition of breeding phenotypes in the rice digital production using spectral technology. In this study, a rapid and accurate inversion of nitrogen content was realized to detect the spectral characteristics and variation in the rice leaves using the character transfer vegetation index in the spectral technology. The results showed that there were all the same changes in the spectral curves of rice leaves in the key growth periods, indicating the extremely significant characteristics of "two valleys and one peak" in each period. The spectral characteristic curve varied significantly in the visible and near-infrared regions in the period of rice growth. Specifically, the spectral curve changed greatly in the near-infrared region from the tillering to the heading stage, whereas, the hyperspectral reflectance increased gradually in each growth period. The characteristic bands of the rice nitrogen content were extracted from the continuous hyperspectral reflectance with lots of redundant information. The vegetation index of nitrogen content inversion was then constructed for the rice leaves. Since the continuous projection was a forward band selection, the projection of each cycle was calculated in the remaining band starting from a band variable, and then the band corresponding to the maximum value of the projection vector was introduced into the band combination, while ensuring the lowest correlation between the selected and previous band, finally to repeat the above steps until the selected number of bands were fully met the given requirements. Therefore, the continuous projection was used to screen the characteristic bands of rice hyperspectral in the band of 400-1000 nm, where the correction set was utilized to conduct the internal cross validation of the selected bands. Six hyperspectral characteristic bands of nitrogen content in rice leaves were screened, i.e., 500, 555, 662, 690, 729, and 800 nm, according to the Root Mean Square Error of Cross Validation (RMSECV) values in the validation. Once the form of vegetation index was determined, the current vegetation index of rice nitrogen content was mostly constructed to change the bands for a new one. The mature form of vegetation index was normally used to determine the optimal band, according to the different inversion parameters. Nevertheless, there was still lacking of relationship between nitrogen content and spectral characteristics. Therefore, the multiple characteristic bands were first converted into three bands for the nitrogen characteristic transfer index, according to the band characteristic transfer. A linear regression model was established to verify the inversion model of nitrogen content in rice leaves. Taking Nitrogen Characteristic Transfer Index (NCTI) as the input, the inversion model of rice nitrogen content was constructed by linear regression. The determination coefficient of the model was 0.774, and the root mean square error was 0.379 mg/g. The inversion performed better, compared with the traditional vegetation indexes, such as NDVI (Normalized Difference Vegetation Index) and EVI (Ratio Vegetation Index). Consequently, the NCTI can be widely expected to serve as a hyperspectral vegetation index for the rapid inversion of nitrogen content in rice leaves in practical application. The finding can provide promising data support and strong reference for the spectral detection of nitrogen content in rice leaves. [ABSTRACT FROM AUTHOR]

Cultivation of blackberry has gradually expanded in Brazil, due to their rusticity and low production cost; thus, it stands out as an excellent option for product diversification. There is a need to improve technical information on the management of this crop, especially mineral nutrition. Knowledge of the visual symptoms of nutritional deficiency and foliar contents of the nutrients allows helps farmers to choose the most adequate fertilization for plants. This study aimed at evaluating nutritional aspects and effects of nutrient omission on the growth of BRS Xingu blackberry. Treatments consisted of complete solutions and individual omission of the following nutrients: nitrogen (N), phosphorus (P), potassium (K), calcium (C), magnesium (Mg), boron (B), manganese (Mn), zinc (Zn) and iron (Fe). The following variables were evaluated: leaf dry matter, root dry matter, total dry mass, macro- and micronutrients contents in leaves and visual symptoms of nutrient deficiency. Macronutrient and B deficiencies limit growth of blackberry omission led to the highest decrease in plant growth, besides leaf wrinkling, a fact that shows that BRS Xingu is susceptible to its deficiency. Correlation was found between N and Ca, N and P and B and Ca leaf contents. Low leaf contents of N, K, Ca and B were observed when these nutrients were omitted from the solution. [ABSTRACT FROM AUTHOR]

To investigate the function of melatonin (MT) on nitrogen uptake and metabolism in soybean, six groups of treatments, with and without 100 µM melatonin were conducted at low, normal, and high nitrogen levels (1.5, 7.5, and 15 mM, respectively). The related indexes of nitrogen metabolism and the antioxidant system of seedlings were measured and analysed. Results indicated that MT could enhance the level of nitrogen metabolism by upregulating the coding genes of enzymes related to nitrogen metabolism and increasing total nitrogen content, especially under low nitrogen levels. Under high nitrogen conditions, the addition of MT not only accelerated ammonium assimilation and utilisation by enhancing the activity of glutamine synthetase involved in ammonium assimilation, but also reduced the extent of membrane lipid peroxidation to alleviate the degree of damage by improving the activity of antioxidant enzymes. In addition, MT enhanced soybean growth with positive effects in morphological changes at different nitrogen levels, including significantly increased stem diameter, total leaf area, and root nodule number, and biomass accumulation. Finally, biomass accumulation increased under low, normal, and high nitrogen levels by 9.80%, 14.06%, and 11.44%, respectively. The results suggested that MT could enhance the soybean tolerance to low and excessive N treatments. [ABSTRACT FROM AUTHOR]

The application and use of image analysis to assess the plant nitrogen (N) status has gained importance especially in precision agriculture for cereal plants using aerial remote sensing or even ground-based commercial N sensors. The objective of this work was to propose the plant growth stage and leaf parts possible to be used in sweet corn plant for N diagnosis using the SPAD chlorophyll meter and a table scanner images. A field experiment was carried out at the Federal University of Viçosa. A randomized block design was used, in a 4x3x5 factorial scheme (growth stages x leaf parts x N doses), with five replications. SPAD reading and scanner images were obtained for Red, Green and Blue (RGB) were obtained using the ImageJ® software. The data were submitted to analysis of variance and Pearson's correlation analysis at a 5% probability. Reading position on the middle part of the leaf at V10 and at R1 growth stages are suitable for assessing sweet corn N status using SPAD with 51.40 and 45.09 as an optimal reference value, respectively. RGB values determined with the scanner also was suitable for assessing the N status of sweet corn. The technique does not require special expertise for its application. It is proposed table containing optimal reference values of SPAD and RGB colors in the medial part of the sweet corn leaf at V10 and R1 development stages of corn plant. [ABSTRACT FROM AUTHOR]

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Accurate acquisition of plant phenotypic information has raised long-standing concerns in support of crop breeding programs. Different methods have been developed for high throughput plant phenotyping, while they mainly focused on the canopy level without considering the spatiotemporal heterogeneity at different canopy layers and growth stages. This study aims to phenotype spatiotemporal heterogeneity of chlorophyll (Chl) content and fluorescence response within rice leaves and canopies. Multipoint Chl content and high time-resolved Chl a fluorescence (ChlF) transient (OJIP transient) of rice plants were measured at different nitrogen levels and growth stages. Results showed that the Chl content within the upper leaves exhibited an increasing trend from the basal to the top portions but a decreasing pattern within the lower leaves at the most growth stages. Leaf Chl content within the rice canopy was higher in the lower leaves in the vegetative phase, while from the initial heading stage the pattern gradually reversed with the highest Chl content appearing in the upper leaves. Nitrogen supply mainly affects the occurrence time of the reverse vertical pattern. This could be the result of different nutritional demands of leaves transforming from sinks to sources, and it was further confirmed by the fall of the JI phase of OJIP transient in the vegetative phase and the rise in the reproductive phase. We further deduced that the vertical distribution of Chl content could have a defined pattern at a specific growth stage. Furthermore, the reduction of end acceptors at photosystem I (PSI) electron acceptor side per cross section (RE0/CS) was found to be a potential sensitive predictor for identifying the vertical heterogeneity of leaf Chl content. These findings provide prior knowledge on the vertical profiles of crop physiological traits, which explore the opportunity to develop more efficient plant phenotyping tools for crop breeding. [ABSTRACT FROM AUTHOR]

Destructive methods for crop nutrition estimation are accurate and standardized but costly and limited by spatial scale. Non-destructive techniques such as the use of digital imaging provide fast and reliable results in situ; however, there is limited information on these non-destructive techniques in leafy vegetable crops. During the study it was estimated the concentration of nitrogen (N) and chlorophyll (Chl) in romaine lettuce using spectral indices derived from the RGB (red, green and blue) digital images. The lettuce crop was grown in plastic tunnels and irrigated with five N levels: 0, 4, 8, 12, and 16 mEq L-1 NO3-N (corresponding to 0, 248, 496 and 744 mg L-1, respectively) based on a modified Steiner solution. The treatment of 16 mEq L-1 NO3-N showed the highest growth at 42 days after transplanting (DAT). Digital images of the plants were acquired weekly with a RGB camera and processed to obtain scale mosaics and twelve spectral vegetation indices. Correlation analysis of the spectral indices indicated that normalized green-red difference index (NGRDI), excess green (ExG) and green channel (g) indices showed a positive linear correlation with the concentration of N (r > 0.93) and Chl (r > 0.93). Besides, an exponential correlation with leaf area (r > 0.86) was founded, which was stronger in the last 21 DAT due to the acceleration in leaf growth during the vegetative stage of the crop. These results show that RGB digital images are a low cost, non-destructive, reliable and accurate method to estimate N and Chl concentration and leaf area in romaine lettuce during production. Therefore, this technique could be an affordable alternative that combined with portable meters (i.e. SPAD) provides real-time monitoring of the nutritional status of the lettuce crop, especially in crop factories. [ABSTRACT FROM AUTHOR]

Shoot architecture is a key component of the interactions between plants and their environment. We present a novel model of grass, which fully integrates shoot morphogenesis and the metabolism of carbon (C) and nitrogen (N) at organ scale, within a three-dimensional representation of plant architecture. Plant morphogenesis is seen as a self-regulated system driven by two main mechanisms. First, the rate of organ extension and the establishment of architectural traits are regulated by concentrations of C and N metabolites in the growth zones and the temperature. Second, the timing of extension is regulated by rules coordinating successive phytomers instead of a thermal time schedule. Local concentrations are calculated from a model of C and N metabolism at organ scale. The three-dimensional representation allows the accurate calculation of light and temperature distribution within the architecture. The model was calibrated for wheat (Triticum aestivum) and evaluated for early vegetative stages. This approach allowed the simulation of realistic patterns of leaf dimensions, extension dynamics, and organ mass and composition. The model simulated, as emergent properties, plant and agronomic traits. Metabolic activities of growing leaves were investigated in relation to whole-plant functioning and environmental conditions. The current model is an important step towards a better understanding of the plasticity of plant phenotype in different environments. [ABSTRACT FROM AUTHOR]

The aim of the study was to evaluate the nitrogen removal and its effects on the plant's growth and leaves morphology. using two subsurface vertical flow (VF bed), with different depths (0.24 m2 × 0.70 m; 0.24 m2 × 0.35 m) and nitrogen load increments. The VF bed were planted with Vetiveria zizanioides, filled with light expanded clay aggregates (Leca®NR 10/20) and fed in parallel mode with synthetic wastewater. High ammonium nitrogen concentration ([NH4+–N] from 68 ± 3 to 290 ± 8 mg L−1) was used without toxicity symptoms in plants, although the effects of ammonium nitrogen load were stopped the growth of the plants. Significant differences between ammonium nitrogen removed in each VF bed obtained for total nitrogen (TNinfl.) ≥ 27 ± 0.8 g m−2 d−1. The nitrification was contributed to ammonium nitrogen removal because was found higher values of nitrate and nitrite in the effluent. These values were more higher in VF bed 1 than in the VF bed 2, since ammonium nitrogen removal were also more higher in VF bed 1 than in the VF bed 2. Total nitrogen mass balance was carried out and the results show that the nitrification/denitrification process occurred with nitrogen plants uptake. It was observed that the VF bed depth has an influence on all nitrogen removal processes. As higher the depth root system it is seemed to favour the creation of zones with different oxidations conditions that allow the nitrogen compounds to be removed intensively. [ABSTRACT FROM AUTHOR]

By modifying two genes involved in lipid biosynthesis and storage [cysteine oleosin (cys-OLE)/diacylglycerol O -acyltransferase (DGAT)], the accumulation of stable lipid droplets in perennial ryegrass (Lolium perenne) leaves was achieved. Growth, biomass allocation, leaf structure, gas exchange parameters, fatty acids, and water-soluble carbohydrates were quantified for a high-expressing cys-OLE/DGAT ryegrass transformant (HL) and a wild-type (WT) control grown under controlled conditions with 1–10 mM nitrogen (N) supply at ambient and elevated atmospheric CO2. A dramatic shift in leaf carbon (C) storage occurred in HL leaves, away from readily mobilizable carbohydrates and towards stable lipid droplets. HL exhibited an increased growth rate, mainly in non-photosynthetic organs, leading to a decreased leaf mass fraction. HL leaves, however, displayed an increased specific leaf area and photosynthetic rate per unit leaf area, delivering greater overall C capture and leaf growth at high N supply. HL also exhibited a greater photosynthesis response to elevated atmospheric CO2. We speculate that by behaving as uniquely stable microsinks for C, cys-OLE-encapsulated lipid droplets can reduce feedback inhibition of photosynthesis and drive greater C capture. Manipulation of many genes and gene combinations has been used to increase non-seed lipid content. However, the cys-OLE/DGAT technology remains the only reported case that increases plant biomass. We contrast cys-OLE/DGAT with other lipid accumulation strategies and discuss the implications of introducing lipid sinks into non-seed organs for plant energy homeostasis and growth. [ABSTRACT FROM AUTHOR]

By modifying two genes involved in lipid biosynthesis and storage [cysteine oleosin (cys-OLE)/diacylglycerol O -acyltransferase (DGAT)], the accumulation of stable lipid droplets in perennial ryegrass (Lolium perenne) leaves was achieved. Growth, biomass allocation, leaf structure, gas exchange parameters, fatty acids, and water-soluble carbohydrates were quantified for a high-expressing cys-OLE/DGAT ryegrass transformant (HL) and a wild-type (WT) control grown under controlled conditions with 1–10 mM nitrogen (N) supply at ambient and elevated atmospheric CO2. A dramatic shift in leaf carbon (C) storage occurred in HL leaves, away from readily mobilizable carbohydrates and towards stable lipid droplets. HL exhibited an increased growth rate, mainly in non-photosynthetic organs, leading to a decreased leaf mass fraction. HL leaves, however, displayed an increased specific leaf area and photosynthetic rate per unit leaf area, delivering greater overall C capture and leaf growth at high N supply. HL also exhibited a greater photosynthesis response to elevated atmospheric CO2. We speculate that by behaving as uniquely stable microsinks for C, cys-OLE-encapsulated lipid droplets can reduce feedback inhibition of photosynthesis and drive greater C capture. Manipulation of many genes and gene combinations has been used to increase non-seed lipid content. However, the cys-OLE/DGAT technology remains the only reported case that increases plant biomass. We contrast cys-OLE/DGAT with other lipid accumulation strategies and discuss the implications of introducing lipid sinks into non-seed organs for plant energy homeostasis and growth. [ABSTRACT FROM AUTHOR]

Human‐induced disturbances, including grazing and clipping, that cause defoliation are common in natural grasslands. Plant functional type differences in the ability to compensate for this tissue loss may influence interspecific competition.To explore the effects of different intensities of clipping and nitrogen (N) addition on compensatory growth and interspecific competition, we measured accumulated aboveground biomass (AGB), belowground biomass (BGB), tiller number, non‐structural carbohydrates concentrations and leaf gas exchange parameters in two locally co‐occurring species (the C3 grass Leymus chinensis and the C4 grass Hemarthria altissima) growing in monoculture and in mixture.For both grasses, the clipping treatment had significant impacts on the accumulated AGB, and the 40% clipping treatment had the largest effect. BGB gradually decreased with increasing defoliation intensity. Severe defoliation caused a significant increase in tiller number. Stored carbohydrates in the belowground biomass were mobilised and transported aboveground for the growth of new leaves to compensate for clipping‐induced injury. The net CO2 assimilation rate (A) of the remaining leaves increased with clipping intensity and peaked under clipping intensities of 20% or 40%. Nitrogen addition, at a rate of 10 g·N·m−2·year−1, enhanced A of the remaining leaves and non‐structural carbohydrate concentrations, which benefited plant compensatory growth, especially for the C3 grass. Under the mixed planting conditions, the clipping and N addition treatments lowered the competitive advantage of the C4 grass.The results suggest that a combination of defoliation and N deposition have the potential to benefit the coexistence of C3 and C4 grasses. [ABSTRACT FROM AUTHOR]

A field experiment was conducted at the summer season of 2017, and then repeated at the summer season of 2018 in Agricultural Research Station. Faculty of Agric., Zigzag Univ., Sharkia Governorate, Egypt. The study investigated the impact of eleven nitrogen and five phosphorus fertilization regimes on some leaf traits 70 days after sowing (DAS) of maize cultivar single hybrid 168. Results showed that, 120kg N/fad., from different sources i.e., chemical fertilizer, compost and biofertilizers were effectless on number of leaves/plant at 70 days after sowing (DAS) of both seasons and their combined analysis. Number of leaves either under or above the ear of mono eared maize plant were not affected due to applying different nitrogen fertilization regimes studied. Leaf area/maize plant was significantly affected in the first season only. The largest leaf erea/plant (4254.22 cm2/plant) was obtained in the first season, with the appliance of the integrated N fertilization regime (90 kg N from chemical fertilizer +30 kg N from compost). Area of leaves under ear resulted from the integrated fertilization regime (cerealine + 60 kg chemical N+ 60 kg N from compost) was larger than that in the control treatment by 30.94% based on combined results. Regarding to the area of leaves above the ear, results of the 1st season displayed that area of leaves above the ear were at par in treatments N2, N3, N4, N5 and N6. Application of either 120kg chemical fertilizer (N2) or 90 kg chemical N +30 kg N from compost (N3) was conjucated with larger values of leaf area index comparably with other regimes. According to combined analysis, ear leaf area ranged from 481.87 cm2 in control treatment to 625.89 cm2 in the integrated nitrogen fertilization regimes comprised of cerealine + 60 kg chemical N/fad. + 60 kgN from compost. From the results of combined analysis, it could be noted that tassel leaf area ranged between 150.99 to 217.87 cm2 under biofertilization (N11) and the integrated fertilization regimes (N8) in the same order. Insignificant phosphorus fertilization effect under study on maize leaf traits studied at 70DAS, was recorded in both seasons and the combined analysis. [ABSTRACT FROM AUTHOR]

Steviol glycosides (SGs) in Stevia (Stevia rebaudiana Bertoni) leaves are important due to their high sweetness and low calorific value. The yield of SGs is dependent on fertilization regimes, but the relationship between nitrogen (N) administration and SGs synthesis is still unclear. In this study, we investigate the effects of N rates on SGs production through hydroponic and plot experiments. The SGs yield was not significantly changed by N fertilization, but leaf SGs concentrations were significantly reduced due to the "dilution effect". Additionally, N addition decreased leaf carbon (C)/N ratio and soluble sugar concentration, accompanied with the inhibited phosphoenolpyruvate carboxylase and L-phenylalanine ammonia_lyase activities. A significant positive correlation between leaf SGs concentrations, C/N ratio and soluble sugar concentration was observed. Overall, we suggest that N-driven Stevia growth negatively affects SGs concentrations. The leaf C/N ratio and soluble sugar changes indicated the occurrence of metabolic reprogramming. Image 1 • N-promoted Stevia growth "diluted" leaf steviol glycosides and soluble sugar concentrations. • The key genes in stevioside synthesis and sugar metabolism were down-regulated by nitrogen. • Leaf sugar metabolism plays crucial roles in the N-steviol glycosides relations. [ABSTRACT FROM AUTHOR]

Respiration processes are well recognized as fundamental for the plant carbon balance, but little attention has been paid to the relationships among respiration rates, environment and genetic variability. This can be of particular interest to understand the differences in net carbon balances in crops as grapevines. Night respiration (Rn) and its associated growth (Rg) and maintenance (Rm) components were evaluated during leaf expansion in two grapevine cultivars (Tempranillo cv. and Garnacha cv.) that differ in their plant growth pattern and carbon balance. Simultaneously, leaf traits as leaf mass area, nitrogen (N) and carbon (C) content were evaluated in order to relate to the respiratory processes and the leaf growth. The results showed the differences in respiration rates associated with the leaf expansion pattern. Tempranillo developed leaves with higher leaf area and lower dry weight per leaf unit than Garnacha. Although differences between cultivars were observed in terms of growth costs in expanding leaves, the maintenance costs were similar for both cultivars. Also, a significant linear regression was found between respiration rates and N content in expanding and mature leaves. The results indicate that differences in structure and nitrogen content of expanding leaves may lead to respiratory differences between cultivars. These results also demonstrate the importance of respiratory cost components in carbon balance calculations in grapevines. [ABSTRACT FROM AUTHOR]

One strategy for plants to adapt to low nitrogen is to reduce shoot growth and allocate more nitrogen and carbon for root growth. The mechanism underlying the response of leaf growth to low-nitrogen remains unknown. In this study, we investigated cell division and elongation in maize leaf growth in response to low-nitrogen by using an integrated approach. Kinematic analysis revealed that low-nitrogen inhibited leaf elongation mainly by shortening length of division zone, reducing cell flux and elemental growth rate. Hormone analysis revealed that changes of gibberellins caused by low-nitrogen correlate with the observed changes in division zone size and elemental growth rate in response to low-nitrogen, suggesting role of gibberellin in low-nitrogen induced inhibition of leaf elongation. RNA-Seq identified that GA20ox4 (GRMZM2G060940), a key enzyme for synthesis of gibberellins, was down-regulated in both division and elongation zone of leaf under low-nitrogen supply. Furthermore, exogenous GA 3 application on low-nitrogen plants restored leaf growth. However, application of gibberellin biosynthesis inhibitor reduced leaf growth. It is concluded that low-nitrogen reduces cell flux and elemental growth rate in maize leaf via reducing gibberellin synthesis. As a result, leaf elongation rate was slower and leaf area was smaller, freeing nitrogen for export to roots. [ABSTRACT FROM AUTHOR]

Genotypic difference in nitrogen responsiveness of maize grain yield has gained considerable attention, however, the underlying physiological mechanism is less understood. Leaf area and plant type are important factors determining biomass production, and both of them are regulated by nitrogen supply. The current research aims to assess whether high nitrogen responsiveness is related to leaf growth and plant type. A 2-year field experiment was conducted with three maize cultivars (BMY, ZD2 and ZD958) differing in nitrogen responsiveness under a wide range of nitrogen supply (0, 60, 120, 180 and 240 kg N ha-1). The links between grain yield, leaf area dynamics, leaf angle and orientation value, and radiation use efficiency were investigated. Nitrogen responsiveness, defined as yield increment per unit of increased nitrogen supply, was 8.3–29.1% higher in ZD958 compared with the other cultivars. The maximum grain yield of ZD958 was 21.4–74.6% higher than that of the other cultivars. With increasing nitrogen supply, the increments in maximum leaf area and linear growth rate of leaf area were greater in ZD958, which was positively correlated with grain yield. The interaction effect between cultivar and nitrogen supply was significant on leaf length, but not on leaf width. Across the combinations between cultivar and nitrogen supply, the variation in grain yield was explained by leaf length rather than leaf width. High nitrogen supply increased leaf angle and reduced leaf orientation value, so as to make the leaf more horizontally distributed. However, this change was less significant in ZD958, indicating that the plant type was more compact under high nitrogen supply in maize cultivars with high nitrogen responsiveness. Radiation use efficiency, defined as the slope of the linear relationship between above-ground biomass produced and cumulated intercepted photosynthetic active radiation (PAR) was 5.2–13.2% higher in ZD958 than that of BMY. In conclusion, with increasing nitrogen supply, the cultivars with fast leaf growth and compact plant type have higher conversion efficiency of intercepted PAR into the above-ground biomass and get higher grain yield. • Nitrogen increased leaf area to a larger extent in the maize cultivar with high N responsiveness. • A compact plant type contributed to high N responsiveness under high N supply. • Grain yield increased via gains in radiation use efficiency under high N supply. [ABSTRACT FROM AUTHOR]

The approach to select new growing media, has been focused on selecting materials only from the physical point of view. The objective of this study was to describe the physiological mechanisms involved in I. wallerana growth when cropped on a broad range of growing media created from alternative components. Results showed a close relationship between I. wallerana growth and fine particle size at the beginning of the experiments. Shoot fresh weight was determined mainly by the root system size. There were small differences in the relative growth rate (RGR) between the control substrate and the thirty alternative substrates tested. The lower RGR values resulted from a decrease in the net assimilation rate and the leaf area ratio. The mechanism involved would be associated with a change in photosynthate partitioning, which favored root growth. A close relationship between growth (as total dry weight) and nitrogen content was found as well. [ABSTRACT FROM AUTHOR]

Glutamine synthetase (GS; EC 6.3.1.2) plays a crucial role in the assimilation and re-assimilation of ammonia derived from a wide variety of metabolic processes during plant growth and development. Here, three developmentally regulated isoforms of GS holoenzyme in the leaf of wheat (Triticum aestivum L.) seedlings are described using native-PAGE with a transferase activity assay. The isoforms showed different mobilities in gels, with GSII>GSIII>GSI. The cytosolic GSI was composed of three subunits, GS1, GSr1, and GSr2, with the same molecular weight (39.2 kDa), but different pI values. GSI appeared at leaf emergence and was active throughout the leaf lifespan. GSII and GSIII, both located in the chloroplast, were each composed of a single 42.1 kDa subunit with different pI values. GSII was active mainly in green leaves, while GSIII showed brief but higher activity in green leaves grown under field conditions. LC-MS/MS experiments revealed that GSII and GSIII have the same amino acid sequence, but GSII has more modification sites. With a modified blue native electrophoresis (BNE) technique and in-gel catalytic activity analysis, only two GS isoforms were observed: one cytosolic and one chloroplastic. Mass calibrations on BNE gels showed that the cytosolic GSI holoenzyme was ~490 kDa and likely a dodecamer, and the chloroplastic GS2 holoenzyme was ~240 kDa and likely a hexamer. Our experimental data suggest that the activity of GS isoforms in wheat is regulated by subcellular localization, assembly, and modification to achieve their roles during plant development. [ABSTRACT FROM AUTHOR]

Variations in leaf mass per unit area (Ma) and foliar concentrations of N, P, C, K, Mg and Ca were determined for 365 trees growing in 23 plots along a West African precipitation gradient ranging from 0.29 to 1.62 m a-1. Contrary to previous studies, no marked increase in Ma with declining precipitation was observed, but savanna tree foliar [N] tended to be higher at the drier sites (mass basis). Generally, Ma was slightly higher and [N] slightly lower for forest vs savanna trees with most of this difference attributable to differences in soil chemistry. No systematic variations in [P], [Mg] and [Ca] with precipitation or between trees of forest vs savanna stands were observed. We did, however, find a marked increase in foliar [K] of savanna trees as precipitation declined, with savanna trees also having a significantly lower [K] than those of nearby forest. These differences were not related to differences in soil nutrient status and were accompanied by systematic changes in [C] of opposite sign. We suggest an important but as yet unidentified role for K in the adaption of savanna species to periods of limited water availability; with foliar [K] being also an important factor differentiating tree species adapted to forest vs savanna soils within the 'zone of transition' of Western Africa. Plants are generally assumed to become more sclerophyllous as precipitation declines - but not in West Africa where leaf mass per unit area actually declines with decreasing rainfall. Foliar potassium concentrations increase dramatically with increasing aridity, also differentiating ecotonal forest and savanna species. This suggests an important but as yet unidentified role for K as a modulator of tropical vegetation structure and function. [ABSTRACT FROM AUTHOR]

Growth control in eukaryotes depends on the TOR kinase, which integrates energy and nutrient signals. In this issue of Developmental Cell , Liu et al. demonstrate that, in plants, inorganic nitrogen and amino acids activate TOR via the GTPase ROP2 to promote cell proliferation and leaf growth in the shoot. [ABSTRACT FROM AUTHOR]

Abstract: After intense debate it is now accepted that nutrients (a bottom-up process) and herbivores (a top-down process) are both important controls of plant productivity in many systems. Besides their direct effects, herbivores may also have profound positive or negative indirect effects that can be modulated by nutrients and time. The interactive relationships between time, nutrient availability and herbivore impacts (direct and indirect) on plant growth dynamics are an emerging research topic that merits further effort. Here we did several experiments in a SW Atlantic marsh to contribute towards that gap by focusing on the dominant plant, Spartina densiflora, and one of the dominant herbivores, the crab Neohelice (Chasmagnathus) granulata, in the marsh. Herbivory by the crab was highly seasonal, with most of the consumption occurring in fall. Even though crabs preferred nutrient enriched leaves, nitrogen content was not the driver of these seasonal variations. Crab herbivory had markedly indirect negative impacts on S. densiflora leaves, reducing their growth rates and increasing their senescence. These deleterious impacts may partially explain the seasonal decline in leaf growth and a net loss in leaf biomass observed in the fall. Fertilization did not seem to alter these processes. Adding nutrients increased leaf growth in the spring, where ambient herbivory was low, but it also increased herbivory in the fall, resulting in similar patterns as the ones observed under non-fertilized conditions. Herbivory by the crab also greatly affected the dynamics of S. densiflora stems. Increases in stem density in relation to initial conditions were larger in non-grazed than in grazed plots regardless of whether nutrients were added or not. Together, these results indicate that, in Southwestern marshes populated by S. densiflora and N. granulata, herbivory by the crab represents an important direct and indirect control of plant growth. Our results also emphasize the importance of considering impacts on growth rates and not only on biomass because not considering reduced growth after herbivory may lead to improper calculations of nutrient cycling or detritus production. [Copyright &y& Elsevier]

The objective of the study was to identify specific plant traits determining adaptation of grass species to defoliation and N availability, and thus having a major impact on species dynamics, primary productivity, and on nutrient cycling in grassland ecosystems. It was specifically examined whether the response of species to defoliation is related to their plasticity in leaf growth and in leaf growth zone components, and whether the response of species to nitrogen is related to their plasticity in root morphology and subsequent N acquisition, and to N losses through leaf senescence. The study was conducted on L. perenne and D. glomerata, two grazing tolerant species from fertile habitats, and on F. arundinacea and F. rubra, two less grazing tolerant species from less fertile habitats. Plants were subjected to repeated defoliation at three cutting heights under both high N and low N supply. Biomass allocation, leaf elongation, characteristics of the leaf growth zone (height and relative growth rate), and root morphology, N uptake and N losses through leaf senescence were evaluated. Under high N supply, L. perenne and D. glomerata showed the greatest tolerance to defoliation, due to a large plasticity in the height of the leaf growth zone and due to compensatory growth, either within the leaf growth zone or between growing leaves. Under low N supply, F. rubra was the only species with the ability to develop a more branched root system and a greater length of tertiary roots than under high N. As a consequence, under low N supply F. rubra had a higher specific N uptake and a higher growth rate than the other species. This slow growing species also showed a higher nitrogen allocation to dead leaves and subsequently a higher potential N loss to leaf litter. [ABSTRACT FROM AUTHOR]

The article discusses a study which investigated the physiological responses of Arabidopsis thaliana to the interaction of iron (Fe) deficiency and nitrogen (N) form. The study utilized 30 three-day-old seedlings that were treated for seven days. Leaf growth and chlorophyll content were highest in NO3-fed seedlings. Meanwhile, root acidification capacity and iron-chelate reductase (FCR) activity were found to be dependent on N form. Study authors concluded that N form and Fe level induce antioxidant responses in rosette leaves.

Background and Aims: Nitrogen availability varies greatly over short time scales. This requires that a well-adapted plant modify its phenotype by an appropriate amount and at a certain speed in order to maximize growth and fitness. To determine how plastic ontogenetic changes in each trait interact and whether or not these changes are likely to maximize growth, ontogenetic changes in relative growth rate (RGR), net assimilation rate (NAR), specific leaf area (SLA) and root weight ratio (RWR), before and after a decrease in nitrogen supply, were studied in 14 herbaceous species. [ABSTRACT FROM PUBLISHER]

Caterpillars and spider mites are herbivores with different feeding mechanisms. Spider mites feed on the cell content via stylets, while caterpillars, as chewing herbivores, remove larger amounts of photosynthetically active tissue. We investigated local and systemic effects of short-term caterpillar and spider mite herbivory on cotton in terms of primary metabolism and growth processes. After short-term caterpillar feeding, leaf growth and water content were decreased in damaged leaves. The glutamate/glutamine ratio increased and other free amino acids were also affected. In contrast, mild spider mite infestation did not affect leaf growth or amino acid composition, but led to an increase in total nitrogen and sucrose concentrations. Both herbivores induced locally increased dark respiration, suggesting an increased mobilization of storage compounds potentially available for synthesis of defensive substances, but did not affect assimilation and transpiration. Systemically induced leaves were not significantly affected by the treatments performed in this study. The results show that cotton plants do not compensate the loss of photosynthetic tissue with higher photosynthetic efficiency of the remaining tissue. However, early plant responses to different herbivores leave their signature in primary metabolism, affecting leaf growth. Changes in amino acid concentrations, total nitrogen and sucrose content may affect subsequent herbivore performance. [ABSTRACT FROM AUTHOR]

Legume–grass interactions have a great influence on grassland primary production and it was recently shown how defoliation of a legume can increase the transfer of fixed N to a neighbouring grass. It has also been shown that defoliation of a plant can increase soil microbial activity and lead to better soil N availability in the rhizosphere of the defoliated plant. We combined these two perspectives and tested whether defoliation of a legume ( Lotus corniculatus) can enhance N nutrition of the neighbouring grass ( Holcus lanatus) by increasing growth of soil decomposer biota and the availability of soil organic matter N for grass uptake. We grew mixtures of L. corniculatus and H. lanatus in grassland soil that included 15N-labelled L. corniculatus litter. In half of the systems, we subjected L. corniculatus to a defoliation treatment mimicking insect larvae feeding. At destructive harvests 1, 3, 9 and 30 days after the last defoliation event, we determined how L. corniculatus defoliation affected decomposer microbes, protozoa and nematodes and whether these changes among decomposers created a feedback on the growth and 15N uptake of the neighbouring H. lanatus. Defoliation reduced the growth and litter-N uptake, but increased shoot N concentration of L. corniculatus. Of the soil variables measured, defoliation doubled the number of bacterial-feeding protozoa, but did not affect the abundance of decomposer microbes and bacterial- and fungal-feeding nematodes. Defoliation did not have statistically significant effects on H. lanatus shoot growth, shoot N concentration or litter-N uptake. Our results demonstrate how defoliation-induced changes in legume ecophysiology can affect the growth of decomposers in soil. However, these effects did not appear to lead to a significant change in the availability of soil organic N to the neighbouring grass. It seems that when positive effects of legume defoliation on grass N nutrition are found in grassland ecosystems, these are more likely to be explained by direct transfer of fixed N rather than changes in the availability of soil organic matter N. [ABSTRACT FROM AUTHOR]

Abstract: The seasonal changes in throughfall (TF) and stemflow (SF) chemistry and the canopy interactions of K+ and N compounds were studied in a Japanese cedar forest near the Sea of Japan. The fluxes of most ions, including non-sea-salt SO4 2−, from TF, SF, and rainfall showed distinct seasonal trends, increasing from autumn to winter, owing to the seasonal west wind, while the fluxes of NH4 + and K+ ions from TF+SF might have a large effect of canopy interactions. The contact angle (CA) of water droplets on leaves decreased with leaf aging, suggesting that surface wettability increases with leaf age. The K+ concentration in TF was negatively correlated with the CA of 1-year-old leaves, while the NH4 + concentration was positively correlated with the CA. The net fluxes of NH4 + and NO3 − from TF were positively correlated with the CA. The increase in wettability may accelerate leaching of K+ or uptake of NH4 +. [Copyright &y& Elsevier]

The extent of nitrogen (N) resorption and the degradability of different protein pools were examined in senescing leaves of an annual herb, Chenopodium album L., grown in two light and N conditions. Both N resorption efficiency (REFF; the proportion of green-leaf N resorbed) and proficiency (RPROF; the level to which leaf N content is reduced by resorption) varied among different growth conditions. During leaf senescence, the majority of soluble and membrane proteins was degraded in all growth conditions. Structural proteins were also highly degradable, implying that no particular protein pool constitutes a non-retranslocatable N pool in the leaf. Leaf carbon/N ratio affected the timing and duration of senescing processes, but it did not regulate the extent of protein degradation or N resorption. Sink?source relationships for N in the plant exerted a more direct influence, depressing N resorption when N sink strength was weakened in the low-light and high-N condition. N resorption was, however, not enhanced in high-light and low-N plants with the strongest N sinks, possibly because it reached an upper limit at some point. We conclude that a combination of several physiological factors determines the extent of N resorption in different growth conditions. [ABSTRACT FROM AUTHOR]

Leaf expansion and xylem cytokinin concentration ([X-CK]) decrease in response to nitrogen (N) deprivation. Debate continues over cause, effect, and correlation. Supporting studies provide, at best, correlative evidence that [X-CK] controls leaf growth in response to N-deprivation, while dissenting studies indicate that leaf growth responses to N can be independent of changes in X-CK supply to leaves. A model is proposed to evaluate the physiological significance to leaf growth of changes in plant and environment N concentrations, and plant CK concentrations. [ABSTRACT FROM PUBLISHER]

Abstract: Leaf area growth and nitrogen concentration per unit leaf area, Na (gm−2 N) are two options plants can use to adapt to nitrogen limitation. Previous work indicated that potato (Solanum tuberosum L.) adapts the size of leaves to maintain Na and photosynthetic capacity per unit leaf area. This paper reports on the effect of N limitation on leaf area production and photosynthetic capacity in maize, a C4 cereal. Maize was grown in two experiments in pots in glasshouses with three (0.84–6.0gNpot−1) and five rates (0.5–6.0gpot−1) of N. Leaf tip and ligule appearance were monitored and final individual leaf area was determined. Changes with leaf age in leaf area, leaf N content and light-saturated photosynthetic capacity, P max, were measured on two leaves per plant in each experiment. The final area of the largest leaf and total plant leaf area differed by 16 and 29% from the lowest to highest N supply, but leaf appearance rate and the duration of leaf expansion were unaffected. The N concentration of expanding leaves (Na or %N in dry matter) differed by at least a factor 2 from the lowest to highest N supply. A hyperbolic function described the relation between P max and Na. The results confirm the ‘maize strategy’: leaf N content, photosynthetic capacity, and ultimately radiation use efficiency is more sensitive to nitrogen limitation than are leaf area expansion and light interception. The generality of the findings is discussed and it is suggested that at canopy level species showing the ‘potato strategy’ can be recognized from little effect of nitrogen supply on radiation use efficiency, while the reverse is true for species showing the ‘maize strategy’ for adaptation to N limitation. [Copyright &y& Elsevier]