Search

• Background and Aims Despite the importance of growth [CO2] and water availability for tree growth and survival, little information is available on how the interplay of these two factors can shape intraspecific patterns of functional variation in tree species, particularly for conifers. The main objective of the study was to test whether the range of realized drought tolerance within the species can be affected by elevated [CO2]. • Methods Intraspecific variability in leaf gas exchange, growth rate and other leaf functional traits were studied in clones of maritime pine. A factorial experiment including water availability, growth [CO2] and four different genotypes was conducted in growth rooms. A 'water deficit' treatment was imposed by applying a cycle of progressive soil water depletion and recovery at two levels of growth [CO2]: 'ambient [CO2]' (aCO2 400 μmol mol-1) and 'elevated [CO2]' (eCO2 800 μmol mol-1). • Key Results eCO2 had a neutral effect on the impact of drought on growth and leaf gas exchange of the most drought-sensitive genotypes while it aggravated the impact of drought on the most drought-tolerant genotypes at aCO2. Thus, eCO2 attenuated genotypic differences in drought tolerance as compared with those observed at aCO2. Genotypic variation at both levels of growth [CO2] was found in specific leaf area and leaf nitrogen content but not in other physiological leaf traits such as intrinsic water use efficiency and leaf osmotic potential. eCO2 increased Δ13C but had no significant effect on δ18O. This effect did not interact with the impact of drought, which increased δ18O and decreased Δ13C. Nevertheless, correlations between Δ13C and δ18O indicated the non-stomatal component of water use efficiency in this species can be particularly sensitive to drought. • Conclusions Evidence from this study suggests elevated [CO2] can modify current ranges of drought tolerance within tree species. [ABSTRACT FROM AUTHOR]

The high-yielding indica rice variety, 'Takanari', has the high rate of leaf photosynthesis compared with the commercial japonica varieties. Among backcrossed inbred lines from a cross between 'Takanari' and a japonica variety, 'Koshihikari', two lines, BTK-a and BTK-b, showed approximately 20% higher photosynthetic rate than that of 'Takanari' for a flag leaf at full heading. This is a highest recorded rate of rice leaf photosynthesis. Here, the timing and cause of the increased leaf photosynthesis in the BTK lines were investigated by examining the photosynthesis and related parameters, as well as mesophyll cell anatomy during ontogenesis. Their photosynthetic rate was greater than that of 'Takanari' in the 13th leaf, as well as the flag leaf, but there were no differences in the 7th and 10th leaves. There were no consistent differences in the stomatal conductance, or the leaf nitrogen and Rubisco contents in the 13th and flag leaves. The total surface area of mesophyll cells per leaf area (TA) in the 13th and flag leaves increased significantly in the BTK lines due to the increased number and developed lobes of mesophyll cells compared with in 'Takanari'. The mesophyll conductance ( g ) became greater in the BTK lines compared with 'Takanari' in the flag leaves but not in the 10th leaves. A close correlation was observed between TA and g . We concluded that the increased mesophyll conductance through the development of mesophyll cells during the reproductive period is a probable cause of the greater photosynthetic rate in the BTK lines. [ABSTRACT FROM AUTHOR]

• Background and Aims Despite the importance of growth [CO2] and water availability for tree growth and survival, little information is available on how the interplay of these two factors can shape intraspecific patterns of functional variation in tree species, particularly for conifers. The main objective of the study was to test whether the range of realized drought tolerance within the species can be affected by elevated [CO2]. • Methods Intraspecific variability in leaf gas exchange, growth rate and other leaf functional traits were studied in clones of maritime pine. A factorial experiment including water availability, growth [CO2] and four different genotypes was conducted in growth rooms. A 'water deficit' treatment was imposed by applying a cycle of progressive soil water depletion and recovery at two levels of growth [CO2]: 'ambient [CO2]' (aCO2 400 μmol mol-1) and 'elevated [CO2]' (eCO2 800 μmol mol-1). • Key Results eCO2 had a neutral effect on the impact of drought on growth and leaf gas exchange of the most drought-sensitive genotypes while it aggravated the impact of drought on the most drought-tolerant genotypes at aCO2. Thus, eCO2 attenuated genotypic differences in drought tolerance as compared with those observed at aCO2. Genotypic variation at both levels of growth [CO2] was found in specific leaf area and leaf nitrogen content but not in other physiological leaf traits such as intrinsic water use efficiency and leaf osmotic potential. eCO2 increased Δ13C but had no significant effect on δ18O. This effect did not interact with the impact of drought, which increased δ18O and decreased Δ13C. Nevertheless, correlations between Δ13C and δ18O indicated the non-stomatal component of water use efficiency in this species can be particularly sensitive to drought. • Conclusions Evidence from this study suggests elevated [CO2] can modify current ranges of drought tolerance within tree species. [ABSTRACT FROM AUTHOR]

Aims Sexes of dimorphic species often differ in ecophysiological traits and display spatial segregation. These differences have been interpreted as an evolved response of the sexes to meet the specific resource demands associated with reproduction. Sexes may differ not only in the amount of resources allocated to reproduction but also in the timing of allocation to reproduction. In this study, we hypothesize that as a consequence of their specific resource demands for reproduction, the sexes of the dune plant Honckenya peploides differ in terms of temporal patterns of water use efficiency and nitrogen use and acquisition. Methods Water use efficiency, as inferred from leaf carbon isotope discrimination (Δ13C), nitrogen use, estimated by leaf nitrogen isotope composition (δ15N), and the foliar carbon and nitrogen contents were measured in males and females at three different points in time. Important Findings Females had greater water use efficiency than males, regardless of time. The ratio of N15 to N14 did not change with time in males, but significantly decreased in August for females. The total N content in the leaf tissues of females decreased as the season progressed, while in males a decrease was only found from April to June and then it remained constant from June to August. A similar pattern, but reversed, was followed by the foliar C/N ratio. Additionally, negative relationships between leaf Δ13C and N content were found at all times for males and only at the end of the season for females. Thus, our hypothesis that sex-specific patterns of nitrogen and water use efficiency will depend on time was supported. Overall, our results highlight the importance of including time in studies of sexual dimorphism, and also the role that physiological specialization plays in meeting the specific demands associated with reproduction. [ABSTRACT FROM AUTHOR]

Substrate salinity is one of the main abiotic factors limiting plant establishment, growth and distribution in coastal habitats. Nevertheless, few studies have investigated the interaction between salt concentration and duration of exposure on the physiology and growth of Carpobrotus edulis, an important invasive plant species growing in coastal dune habitats. In this study, four salinity treatment cycles of different length (three, six, twelve and twenty-four days) at salinity of 0 M, 0.1 M, 0.2 M and 0.3 M were imposed. A significant response in plant growth was elicited after 24 days of treatment. The main shoot length (MS L ) and stem biomass (SB MS ) increased by 11% and 4%, respectively at 0.1 M and by 25% and 6% at 0.2 M compared with the control. At 0.3 M MS L did not significantly differ from the control while SB MS was 18% lower. Moreover, C. edulis showed a high photoprotection mechanism efficiency resulting in a high carotenoid to chlorophyll ratio increase which was two, three and four times higher than the control at 0.1 M, 0.2 M and 0.3 M, respectively. Photochemically, the quantum yield of photosynthesis (Φ PSII ) was 17%, 50% and 52% lower than the control at 0.1 M, 0.2 M and 0.3 M. The Φ PSII decrease was associated with a low leaf nitrogen content (N L ) decrease (16%, 21% lower than the control at 0.1 M and 0.2 M, respectively). By contrast, N L had the highest decrease (41% lower than the control) at 0.3 M, which constrains the growth capacity. Overall, C. edulis was able to modulate its response to salinity. The salt stimulated shoot elongation at low or moderate salt concentrations could confer a competitive advantage making C. edulis even more efficient in establishing within the areas which it colonizes. Since the expansion of C. edulis may be enhanced by the forecasted increase in soil salinity, it will be of paramount importance to apply effective management practices in areas invaded by C. edulis to limit its expansion and preserve the native plant biodiversity. [ABSTRACT FROM AUTHOR]

Determining the photosynthetic parameters is the basis for understanding the physiological causes of water saving and yield increasing under drip irrigation modes. In this study, intrinsic photosynthetic parameters were determined during four years experiments in winter wheat field treated with six drip irrigation modes (T1 to T6, stands for treatments of lower irrigation amount with straw mulch, lower irrigation amount without straw mulch, moderate irrigation amount with straw mulch, moderate irrigation amount without straw mulch, higher irrigation amount with straw mulch, and higher irrigation amount without straw mulch, respectively). The differences in photosynthetic parameters among treatments were statistically analyzed, and the correlations between photosynthetic parameters and crop yield were analyzed. The results showed that increasing irrigation amount and straw mulch enhanced the apparent photon quantum efficiency (α), photosynthetic capacity (Amax), maximum carboxylation rate (Vcmax) and maximum electron transfer rate (Jmax), respectively. However, the interaction effects of irrigation amount and mulching on photosynthetic parameters were not significant (p > 0.1). The effect of drip irrigation on apparent quantum efficiency (α) was significant (P < 0.05) during the late periods of the heading and grain filling stages, while the effect of straw mulch on α was not significant (P > 0.1). The effect of straw mulch and drip irrigation on Amax show significant (P < 0.05) seasonal differences. The effects of drip irrigation on Vcmax and Jmax were significant (P < 0.05) during the mid-season periods of the heading and grain filling stages, while the effects of straw mulch were significant (P < 0.05) during the later periods of the heading and grain filling stages. The results of multiple comparisons showed that the photosynthetic parameters of T5 were the highest (P < 0.05). Except for the measurements in 2016, the corresponding values of T6 and T3 were slightly lower but with no significant difference from those of T5 (P > 0.1). However, the corresponding values of T2 were significantly lower (P < 0.05) than those of T5. These results suggested that, under higher irrigation amount, photosynthetic parameters were not affected significantly (P > 0.05) by mulching, but under lower irrigation amount, the parameters significantly (P < 0.05) decreased if treated with no mulching. The average values of Amax during the four years from T1 to T6 were 29.59, 26.45, 31.44, 28.68, 32.42 and 30.90 μmol/ (m2·s), respectively. The average values of Vcmax during the four years from T1 to T6 were 121.42, 107.68, 133.42, 113.55, 141.83 and 129.95 μmol/ (m2·s), respectively. From the point of view of reducing the amount of irrigation, T3 irrigation scheduling can be used as an optimal strategy for winter wheat under drip irrigation with straw mulch, indicating that 65% to 85% of the field capacity was used as the lower and upper limits of soil moisture control. The management practices of drip irrigation with straw mulch can keep the higher photosynthetic capacity of flag leaf for winter wheat. The differences in Amax and Vcmax among treatments could be explained by the leaf nitrogen content (Nmass). Grain yield for all years were also linearly related to Amax and Vcmax, respectively. Therefore, by measuring Nmass, one can estimate Amax and Vcmax, thus achieving the yield estimates of winter wheat field in this area. In addition, the photosynthetic characteristic parameters can also be applied to the crop model to improve the accuracy of model prediction under different water and mulch regimes. [ABSTRACT FROM AUTHOR]

Overgrazing has resulted in widespread decline in biodiversity and ecosystem functioning in grasslands world-wide in recent decades. However, few studies have examined the patterns and thresholds of grazing-induced changes in community structure and ecosystem functioning along a grazing gradient and based on species-level responses and plant functional traits., To identify the thresholds of grazing intensity (GI) at both species and community levels, we conducted a grazing manipulation experiment with seven levels of GI (0-9 sheep ha−1) and two topographies (flat vs. slope) in a typical steppe. Four plant functional traits were measured, including specific leaf area ( SLA), plant height, leaf nitrogen content ( LNC) and stem: leaf ratio., The threshold of GI that significantly altered community composition was at 3·75 sheep ha−1 for the flat system and 3·0 sheep ha−1 for the slope system. For both flat and slope systems, the threshold GI for changes in primary productivity was at 3·0 sheep ha−1, beyond which the productivity decreased substantially., At the species level, the abundances of common species, most of which are perennial grasses, declined at moderate grazing intensities (3·0-4·5 sheep ha−1). The abundances of most rare species, which are perennial forbs, declined at low grazing intensities (1·5-3·0 sheep ha−1). SLA and LNC are good predictors of species-level responses to grazing. Low SLA and high LNC species are negatively affected by high GI, while high SLA and low LNC species are little affected by grazing. The negative effect of GI on species' abundance was greater in the slope system than in the flat system., Synthesis and applications. Our results indicate that the structural and functioning thresholds of grazing intensity depend on plant traits and species composition, which is mediated by topographic location. These findings, integrating plant functional traits and threshold approaches, have important implications for determining sustainable grazing intensity in grassland management and biodiversity conservation in semi-arid regions. [ABSTRACT FROM AUTHOR]

Light propagation modeling in 3-dimensional virtual scenes has been successfully applied to many fields, including plant canopies. However, its application to detailed analyses on how multiple scattering affects spectral-based biochemistry assessments has never been proposed. In this article, a wheat canopy model has been built using simulation models included in the open source software platform Open-Alea. Adel-Wheat, a 3D dynamic model of the aerial growth of winter wheat, has been associated with spectra collected on wheat leaves with an ASD spectrometer, and then used as input of the Caribu light propagation model. Caribu calculates the proportion of direct and scattered light for all polygons of the 3D scene. Principal component analysis was first applied to analyze the distribution of resulting spectra in the spectral feature space. Then the influence of canopy structure on quantitative regression models has been considered. For this purpose, a typical agronomical problem, i.e. nitrogen content retrieval, was addressed, using a Partial Least Square regression model. This study exhibits some important results concerning the distribution of collected spectra in the spectral feature space due to multiple scattering, and underlines the physical interpretation of these results. In the short term, it shows that satisfactory nitrogen content prediction (error about 0.5% of dry matter) can be obtained at the plant level, when considering only the plant top leaves. Moreover, its paves the way for future researches to develop spectral analysis tools able to overcome such multiple scattering phenomena. [ABSTRACT FROM AUTHOR]

PREMISE OF THE STUDY:: Timing of budburst (DBB) may be related to the functional traits and distributions of woody species in temperate regions. Although many previous studies have investigated DBB in a number of temperate species, it has seldom been linked to multiple plant trait relationships. METHODS:: DBB and plant traits were investigated for 24 woody species for 2 years in a warm‐temperate secondary forest in Japan. Particular attention was paid to differences in trait relationships between coexisting deciduous and evergreen broad‐leaved species. KEY RESULTS:: DBB was correlated with plant traits in deciduous but not evergreen broad‐leaved species; DBB was later for deciduous species with greater leaf mass, leaf area, vessel diameter, and leaf nitrogen content per unit mass. In addition, DBB was later for species with more northern distributions in deciduous and evergreen species. CONCLUSIONS:: Clear differences in the trait relationships between deciduous and evergreen broad‐leaved species might be caused by different selection pressures on DBB; selection is expected to be more severe in deciduous species. Overall, the continuous variable of vessel diameter might be used as a simple and effective trait to predict DBB of deciduous species regardless of wood anatomy; however, no such traits were detected as effective predictors of DBB in evergreen species at this study site. In addition, DBB was earlier for the species of more southern distributions, suggesting that such species benefit more from warming. [ABSTRACT FROM AUTHOR]

In the central highlands of Madagascar, blast, a serious fungal disease of rice caused by Magnaporthe oryzae , was shown to be less severe in conservation agriculture (CA) than in conventional tillage (CT) cropping systems. To assess the effects of CA cropping systems on rice susceptibility to blast and to understand the mechanisms involved, an experiment was conducted over three growing seasons in two sites (at high and mid-altitude). Two fertilization treatments, one with mineral nitrogen (N) fertilizer, and one without, were studied in interaction with two different cropping systems (CA/CT) and two rice varieties that differ in their susceptibility to blast. The performances of the two cropping systems were assessed, and results showed that yields were no higher in the CA or were lower than in CT cropping systems. The effects of the treatments on upland rice crop growth were measured by leaf N content as an indicator of N crop status, and leaf area index (LAI) as an indicator of canopy density. In all years at both sites, leaf N content during early growth stages was higher in the CT than in the CA cropping system. The LAI was lower in the CA than in the CT cropping system at the high altitude site in all three years, and in two out of three seasons at the middle altitude site. Overall, when the level of blast was high, blast was less severe in the CA cropping system and with no N fertilizer. Leaf N content and LAI were used as intermediate explanatory variables in the statistical analyses, and one or the other or both always masked the effect of the cropping system or of N fertilization. Our results show that leaf N content during early growth stages masks the effect of the cropping system on leaf blast severity. When the LAI is strongly affected by the cropping system, it also masks the effect of the cropping system on the severity of leaf and panicle blast. Very often both variables masked the effects of the cropping system and of N fertilization. These findings should help improve disease management by modifying fertilization practices and crop nutrition in conservation agriculture cropping systems. [ABSTRACT FROM AUTHOR]

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

Nitrogen (N) deposition has been increasing globally and has arisen concerns of its impacts on terrestrial ecosystems. Ecological indicators play an important role in ecosystem monitoring, assessment and management in the context of an anthropogenic transformation of the global N cycle. By integrating species composition and leaf N stoichiometry, a new community N indicator was defined and validated in the understory plots of an N enrichment (as NH 4 NO 3 ) experiment in an old-growth boreal forest in Northeast China. Three-year N additions showed no significant effect on the understory species richness, but an obvious shift in species composition occurred. The response of leaf N content to N additions was generally positive but varied by species. Overall, the community N indicator increased significantly with higher N addition level and soil available N content, being in the shape of a non-linear saturation response curve. The results suggest that the community N indicator could be an effective tool to indicate changes in ecosystem N availability. Critical values of the community N indicator for specific vegetation type could potentially provide useful information for nature conservation managers and policy makers. [ABSTRACT FROM AUTHOR]

Increasing the rate of leaf photosynthesis is one important approach for increasing grain yield in rice (Oryza sativa). Exploiting the natural variation in CO2 assimilation rate (A) between rice cultivars using quantitative genetics is one promising means to identify genes contributing to higher photosynthesis. In this study, we determined precise location of Carbon Assimilation Rate 8 (CAR8) by crossing a high-yielding indica cultivar with a Japanese commercial cultivar. Fine mapping suggested that CAR8 encodes a putative Heme Activator Protein 3 (OsHAP3) subunit of a CCAAT-box-binding transcription factor called OsHAP3H. Sequencing analysis revealed that the indica allele of CAR8 has a 1-bp deletion at 322 bp from the start codon, resulting in a truncated protein of 125 amino acids. In addition, CAR8 is identical to DTH8/Ghd8/LHD1, which was reported to control rice flowering date. The increase of A is largely due to an increase of RuBP regeneration rate via increased leaf nitrogen content, and partially explained by reduced stomatal limitation via increased stomatal conductance relative to A. This allele also increases hydraulic conductivity, which would promote higher stomatal conductance. This indicates that CAR8 affects multiple physiological aspects relating to photosynthesis. The detailed analysis of molecular functions of CAR8 would help to understand the association between photosynthesis and flowering and demonstrate specific genetic mechanisms that can be exploited to improve photosynthesis in rice and potentially other crops. [ABSTRACT FROM AUTHOR]

Many exotic species have little apparent impact on ecosystem processes, whereas others have dramatic consequences for human and ecosystem health. There is growing evidence that invasions foster eutrophication. We need to identify species that are harmful and systems that are vulnerable to anticipate these consequences. Species' traits may provide the necessary insights., We conducted a global meta-analysis to determine whether plant leaf and litter functional traits, and particularly leaf and litter nitrogen (N) content and carbon: nitrogen (C : N) ratio, explain variation in invasive species' impacts on soil N cycling., Dissimilarity in leaf and litter traits among invaded and noninvaded plant communities control the magnitude and direction of invasion impacts on N cycling. Invasions that caused the greatest increases in soil inorganic N and mineralization rates had a much greater litter N content and lower litter C : N in the invaded than the reference community. Trait dissimilarities were better predictors than the trait values of invasive species alone., Quantifying baseline community tissue traits, in addition to those of the invasive species, is critical to understanding the impacts of invasion on soil N cycling. [ABSTRACT FROM AUTHOR]

Excessive fertilization is common in North China Plain. It is essential to determine the extent to which reduction of nitrogen application rates has little impact on yield and understand its physiological basis. Two seasons of field experiments were conducted in a winter wheat field with three nitrogen (N) fertilization treatments, i.e. N3, traditional N application rates (290 kg N hm −2 ), N2, ∼65% N application rates of N3 (190 kg N hm −2 ) and N1, ∼40% N application rates of N3 (110 kg N hm −2 ). Yield ( Y ) and water use efficiency (WUE) of N2 did not reduce significantly in both seasons despite that the instantaneous net photosynthetic rates ( A n ) and stomatal conductance ( g s ) of N2 were significantly lower than those of N3. Y and WUE of N1 treatment reduced significantly in the second season. The reduction of Y was better indicated by photosynthetic capacity ( A max ) in the grain filling stage (around 48–50 days after the irrigation of reviving stage , Dari 48–50) because the decrease of A max in this stage was proportional to Y . The A max and apparent quantum efficiency (α) of N2 measured on Dari 48–50 were not significantly lower than those of N3, which could be the reason of no significant reduction of Y for N2. Thus, the fertilization amount of N2 (190 kg N hm −2 ) can be applied in this area to keep Y steady for at least two years. Differences of the relationships between A max and biological factors among treatments and non-stomatal limitation of photosynthesis were also discussed. These results are important for understanding the mechanisms of yield reduction by reducing N application and provide scientific basis for application of fertigation. [ABSTRACT FROM AUTHOR]

Nitrogen (N) and water are key resources for leaf photosynthesis and the growth of whole plants. Within-branch leaves need different amounts of N and water to support their differing photosynthetic capacities according to light exposure. To test this scheme, we measured the within-branch investments of N and water and their effects on photosynthetic traits in two deciduous tree species Paulownia tomentosa and Broussonetia papyrifera. We found that leaf photosynthetic capacity gradually increased from branch bottom to top (i.e. from shade to sun leaves). Concomitantly, stomatal conductance (g s) and leaf N content gradually increased, owing to the symport of water and inorganic mineral from root to leaf. Variation of leaf N content led to large gradients of mesophyll conductance, maximum velocity of Rubisco for carboxylation, maximum electron transport rate and leaf mass per area (LMA). Correlation analysis indicated that the within-branch difference in photosynthetic capacity was mainly related to g s and leaf N content, with a relatively minor contribution of LMA. Furthermore, the simultaneous increases of g s and leaf N content enhanced photosynthetic N use efficiency (PNUE) but hardly affected water use efficiency. Therefore, within-branch adjustment of N and water investments is an important strategy used by plants to optimize the overall photosynthetic carbon gain and PNUE. • Within-branch photosynthetic gradients are measured in two field-grown trees. • Within-branch leaves display large variations of leaf N content, g s , g m , A N and PNUE. • Within-branch gradient of A N is related to leaf N content, g s and g m. • Leaf mass per area plays a minor role in determining mass-based A N. • Coordinated investments of N and water increase A N and PNUE of whole plant. [ABSTRACT FROM AUTHOR]

The leaf maximum rate of carboxylation (V cmax ) is a key parameter of plant photosynthetic capacity. The accurate estimation of V cmax is crucial for correctly predicting the carbon flux in the terrestrial carbon cycle. V cmax is correlated with plant traits including leaf nitrogen (N area ) and leaf photosynthetic pigments. Proxies for leaf chlorophyll (Chl area ) and carotenoid contents (Car area ) need to be explored in different ecosystems. In this study, we evaluated the relationship between leaf maximum rate of carboxylation (scaled to 25°C; V cmax25 ) and both leaf N area and photosynthetic pigments (Chl area and Car area ) in winter wheat in a farmland ecosystem. Our results showed that V cmax25 followed the same trends as leaf Chl area . However, leaf N area showed smaller dynamic changes before the flowering stage, and there were smaller seasonal variations in leaf Car area . The correlation between leaf V cmax25 and leaf Chl area was the strongest, followed by leaf Car area and leaf N area (R 2  = 0.69, R 2  = 0.47 and R 2  = 0.36, respectively). The random forest regression analysis also showed that leaf Chl area and leaf Car area were more important than leaf N area for V cmax25 . The correlation between leaf V cmax25 and N area can be weaker since nitrogen allocation is dynamic. The estimation accuracy of the V cmax25 model based on N area , Chl area , and Car area (R 2  = 0.75) was only 0.05 higher than that of the V cmax25 model based on Chl area and Car area (R 2  = 0.70). However, the estimation accuracy of the V cmax25 model based on Chl area and Car area (R 2  = 0.70) was 0.34 higher than that of the V cmax25 model based on N area (R 2  = 0.36). These results highlight that leaf photosynthetic pigments can be a predictor for estimating V cmax25 , expanding a new way to estimate spatially continuous V cmax25 on a regional scale, and to improve model simulation accuracy., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Li, Wang, Fu, Qiao, Hao and Qi.)

We measured nitrogen stable isotope values (δ15N), and total phosphorus (%P) and total nitrogen (%N) contents in leaves of the temperate mangrove (Avicennia marina sp. australasica) from three coastal ecosystems exposed to various levels of human impact (Manukau, high; Mangawhai, low; and Waitemata, intermediate) in northern New Zealand. We measured δ15N values around 10 in environments where the major terrestrial water inputs are sewage. The highest average h total nitrogen contents and δ15N values were found in the Auckland city region (Manukau Harbour) at 2.2%N and 9.9h, respectively. The lowest values were found in Mangawhai Harbour, situated about 80 km north of Auckland city, at 2.0%N and 5.2, respectively. In the Waitemata Harbour, also located in Auckland city but with less exposur h e to human derived sewage inputs, both parameters were intermediate, at 2.1%N and 6.4h. Total phosphorus contents did not vary significantly. Additionally, analysis of historical mangrove leaf herbarium samples obtained from the Auckland War Memorial Museum indicated that a reduction in both leaf total nitrogen and δ15N content has occurred over the past 100 years in Auckland's harbors. Collectively, these results suggest that anthropogenically derived nitrogen has had a significant impact on mangrove nutrient status in Auckland harbors over the last 100 years. The observed decrease in nitrogenous nutrients probably occurred due to sewage system improvements. We suggest that mangrove plant physiological response to nutrient excess could be used as an indicator of long-term eutrophication trends. Monitoring leaf nutrient status in mangroves can be used to assess environmental stress (sewage, eutrophication) on coastal ecosystems heavily impacted by human activities. Moreover, nitrogen and phosphorus leaf contents can be used to assess levels of available nutrients in the surrounding environments. [ABSTRACT FROM AUTHOR]

Nitrogen (N) content is an important factor that can affect wheat production. The non-destructive testing of wheat canopy leaf N content through multi-angle hyperspectral remote sensing is of great importance for wheat production and management. Based on a 2-year experiment for winter wheat in Lethbridge (Canada), Zhengzhou (China), and Kaifeng (China) growing under different cultivation practices, the authors studied the relationships between N content and wheat canopy spectral data in solar principal plane (SPP) and perpendicular plane (PP) at different observation angles. Modeling was conducted according to the spectrum index with the highest correlation coefficient and the corresponding observation angle. The results showed that correlation coefficient between the spectral index and canopy leaf N content at each observation angle of the SPP was significantly higher than that of the PP. Significant differences in the correlation coefficient were also observed at different observation angles of the same observation plane, and the correlation coefficients of angles of −30° and −40° were higher than others. A model fitted by a power function by using mND705 as independent variable at an angle of −40° in the SPP showed the highest accuracy. [ABSTRACT FROM AUTHOR]

The estimation of crop nitrogen status in fresh vegetation leaf using field spectroscopy is challenging due to the weak responses on leaf/canopy reflectance and the overlapping with the absorption features of other compounds. Although the spectral indices were proposed in the literature to predict leaf nitrogen content (LNC), the performance of selected spectral indices to estimate the LNC is often inconsistent. Moreover, the models for nitrogen content estimation changed with the growth stage. The goal of this study was to evaluate the performance of published indices, ratio of data difference index (RDDI) and ratio of data index (RDI) developed by band iterative-optimization algorithm in LNC estimation. The correlation analysis, linear regression and cross validation were used to analyze the relationship between spectral data and LNC and construct the best performed estimation model. The study was conducted by the data of five growing seasons of litchi from the orchards in Guangdong Province of China. Results showed that the relationship between chlorophyll (Chl) related spectral indices and LNC varied with the growth stage. Even in flower bud morphological differentiation stage and autumn shoot maturation stage, there were not significant correlations between the proposed spectral indices and LNC. Besides it is difficult to estimate the LNC by the general model across the growth stages due to the integrated effects of cultivar, biochemical, canopy structure, etc. The band iterative-optimization algorithm can improve the sensitivity of spectral data to LNC to some extent. The optimal RDDI performed better than other indices for the synthetic dataset and the dataset in each growth stage. And the sensitive bands selected in the optimal indices at each growth stage are not consistent, which are not only related to the Chl absorption but also other biochemical components, such as starch, lignin, cellulose, protein, etc. In general, the LNC can be estimated by the optimized CR-based RDDI indices in autumn shoot maturation stage, flower spike stage, fruit maturation stage, and flowering stage with the R 2 > 0.50 and RMSE < 0.14. Although there were the significant relationship between RDIs and RDDIs in flower bud morphological differentiation stage, the highest R 2 s of the model developed by RDDIs and RDIs were less than 0.50 in cross validation. This study indicated that the applicability of canopy reflectance to estimate litchi LNC was closely related to the growth stage of litchi. Growth stage-specific models will be preferred for estimating litchi LNC estimation. [ABSTRACT FROM AUTHOR]

Nitrogen (N) supply significantly influences plant growth and crop yields. To investigate the dynamic process of wheat plant responses to nitrogen management, digital infrared thermography was used to detect canopy average temperature (CAT) during different wheat growth stages in three field management experiments, including N applied rates, N application methods and cultivation approaches, which were conducted in 2013–2014 in southeast China. The CAT was reduced with increased N rates, compared to the control (0 N), applications of 300 kg N ha −1 reduced CAT by 14.0%, 10.7% and 9.2% at the tillering, heading and milking stages, respectively. The CAT was also sensitive to N application methods, in which the CAT of the farmers’ fertilizer practice (FFP) was lower and higher than that of the optimal N management (OPT) before the heading stage and after the heading stage, respectively. Considering the cultivation approaches, the effects of deep tillage (NC-DP) on the CAT was more efficient than normal cultivation (NC) in wheat production. Lower CAT was observed for higher wheat biomass and yield, as a result of the CAT being somewhat negatively correlated with leaf N content. The wheat yield could be estimated by monitoring the CAT based on the response curves of the grain yield and CAT to the N addition rate, which was associated with stomatal conductance and transpiration rate. In conclusion, our results indicated that canopy temperature may provide an effective tool for dynamical monitoring of wheat growth and yields. [ABSTRACT FROM AUTHOR]

Hyperspectral LiDAR (HSL) is a novel tool in the field of active remote sensing, which has been widely used in many domains because of its advantageous ability of spectrum-gained. Especially in the precise monitoring of nitrogen in green plants, the HSL plays a dispensable role. The exiting HSL system used for nitrogen status monitoring has a multi-channel detector, which can improve the spectral resolution and receiving range, but maybe result in data redundancy, difficulty in system integration and high cost as well. Thus, it is necessary and urgent to pick out the nitrogen-sensitive feature wavelengths among the spectral range. The present study, aiming at solving this problem, assigns a feature weighting to each centre wavelength of HSL system by using matrix coefficient analysis and divergence threshold. The feature weighting is a criterion to amend the centre wavelength of the detector to accommodate different purpose, especially the estimation of leaf nitrogen content (LNC) in rice. By this way, the wavelengths highcorrelated to the LNC can be ranked in a descending order, which are used to estimate rice LNC sequentially. In this paper, a HSL system which works based on a wide spectrum emission and a 32-channel detector is conducted to collect the reflectance spectra of rice leaf. These spectra collected by HSL cover a range of 538 nm - 910 nm with a resolution of 12 nm. These 32 wavelengths are strong absorbed by chlorophyll in green plant among this range. The relationship between the rice LNC and reflectance-based spectra is modeled using partial least squares (PLS) and support vector machines (SVMs) based on calibration and validation datasets respectively. The results indicate that I) wavelength selection method of HSL based on feature weighting is effective to choose the nitrogen-sensitive wavelengths, which can also be co-adapted with the hardware of HSL system friendly. II) The chosen wavelength has a high correlation with rice LNC which can be retrieved by using PLS and SVMs regression methods. [ABSTRACT FROM AUTHOR]

Hyperspectral LiDAR (HSL) is a novel tool in the field of active remote sensing, which has been widely used in many domains because of its advantageous ability of spectrum-gained. Especially in the precise monitoring of nitrogen in green plants, the HSL plays a dispensable role. The exiting HSL system used for nitrogen status monitoring has a multi-channel detector, which can improve the spectral resolution and receiving range, but maybe result in data redundancy, difficulty in system integration and high cost as well. Thus, it is necessary and urgent to pick out the nitrogen-sensitive feature wavelengths among the spectral range. The present study, aiming at solving this problem, assigns a feature weighting to each centre wavelength of HSL system by using matrix coefficient analysis and divergence threshold. The feature weighting is a criterion to amend the centre wavelength of the detector to accommodate different purpose, especially the estimation of leaf nitrogen content (LNC) in rice. By this way, the wavelengths high-correlated to the LNC can be ranked in a descending order, which are used to estimate rice LNC sequentially. In this paper, a HSL system which works based on a wide spectrum emission and a 32-channel detector is conducted to collect the reflectance spectra of rice leaf. These spectra collected by HSL cover a range of 538 nm - 910 nm with a resolution of 12 nm. These 32 wavelengths are strong absorbed by chlorophyll in green plant among this range. The relationship between the rice LNC and reflectance-based spectra is modeled using partial least squares (PLS) and support vector machines (SVMs) based on calibration and validation datasets respectively. The results indicate that I) wavelength selection method of HSL based on feature weighting is effective to choose the nitrogen-sensitive wavelengths, which can also be co-adapted with the hardware of HSL system friendly. II) The chosen wavelength has a high correlation with rice LNC which can be retrieved by using PLS and SVMs regression methods. [ABSTRACT FROM AUTHOR]

The nitrogen content of leaves in rice plants at various planting densities in the field and under high and low levels of nitrogen in pots were comparatively examined, and thereby the effect of the nitrogen content of leaves on the nodal positions of the last visible primary tiller on the main stem was clarified. The nodal positions of the last visible primary tiller, which determine the potential number of cumulative tillers, were negatively correlated with the planting density. However, critical nitrogen contents of leaves for tillering on a leaf-area basis (NA), and those on a dry-weight basis (NW) were estimated as 1.4-1.6 g m-2, and 3.8-4.5%, respectively, at the time when the last visible primary tiller emerged, even when the planting densities varied from 24 to197 plants m-2. The critical NA for tillering of rice plants grown under high and low levels of nitrogen fertilization was also nearly the same at the time when the primary tiller ceased to emerge. Therefore, the higher nodal position of the last visible primary tiller caused by lower plant density was attributable to the delayed canopy development and delayed competition for soil nitrogen resources. Suppression of the emergence of the primary tiller when the NA was less than 1.6 g m-2 by an insufficient supply of nitrogen was explained satisfactorily by assuming an insufficient supply of assimilates from leaves to a primary tiller bud.

We found in the previous study that the wheat plants grown under relatively low soil moisture conditions (D plot) could attain heavier dry matter than the plants watered on the basis of average local precipitation (W plot). The aim of this study was to make a detail analysis of the ecophysiological characteristics that cause the difference in dry matter production between the plants in the W and D plots under different soil moisture conditions. Soil matric potential at a depth of 30 cm was kept at about −4 kPa in the W plot. It decreased gradually after watering at about one month before heading and at heading, reaching about −80 kPa at heading stage and at the mid-ripening stage respectively, in the D plot. The plants in the D plot produced heavier dry matter and a better developed root system than the plants in the W plot. The higher net assimilation rate and larger leaf area, which accounted for the higher crop growth rate of the D plot, weredue both to avoiding suppression of the photosynthetic rate and leaf expansion owing to water stress, and to maintaining high rates of leaf photosynthesis and a large leaf area during leaf senescence. A larger amount of nitrogen was accumulatedat the flowering stage and the nitrogen content of leaves remained higher during senescence in plants in the D plot than those in the W plot. The activity of cytokinins in the xylem sap was higher in plants in the D plot. These characteristics might have contributed to the delay in the decline in the rate of photosynthesis and in leaf area during leaf senescence and seemed to be supported by the enhanced development of the root system under moisture-restricted conditions.

Six chlorophyll meters (SPAD) were compared to determine the magnitude of differences in SPAD readings on rice leaves. Correlations among the six SPAD meters were statistically significant (P

To clarify the factors responsible for the maintenance of a high rate of photosynthesis at the ripening stage in the high-yield rice cultivar Akenohoshi, as compared with that in a Japanese standard cultivar, Nipponbare, we investigated the nitrogen content of leaves, focusing on the accumulation and the partitioning of nitrogen in rice plants. The nitrogen content of leaves of plants that were grown in the field or in pots remained higher in Akenohoshi than in Nipponbare during the ripening stage, and there was a close correlation between the rate of photosynthesis and the nitrogen content irrespective of cultivar and treatment. The accumulation of nitrogen in the whole plant was greater in Akenohoshi than in Nipponbare before heading and during the ripening stage. The extent of partitioning of nitrogen to leaves was higher and that to ears was lower in Akenohoshi than in Nipponbare during the ripening stage. By application of additional nitrogen fertilizer to Nipponbare, the nitrogen content of leaves was increased as a result of the increased accumulation of nitrogen in the whole plant and the enhanced partitioning of nitrogen to leaves. Our results indicate that the higher nitrogen content of Akenohoshi leaves was due to the greater accumulation of nitrogen in the plant before heading and during the ripening stage and the more effective partitioning of nitrogen to leaves during the ripening stage, which resulted in the maintenance of a high rate of photosynthesis during ripening.

Field experiments were conducted to evaluate cotton growth and yield response to nitrogen and sulfur applications at the experimental areas of Department of Field Crops, Çukurova University, Adana, Turkey, in 2011 and 2012. Sulfur treatments of 0, 15, 30, 45, and 60 kg S ha-1 were broadcast at planting. Nitrogen treatments of 0, 60, 120, 180, and 240 kg N ha-1 were divided in to three dosage. Important increases in number of fruiting branches and open bolls per plant and seed cotton yield were measured at 30 kg S ha-1 while no significant increase was observed at 60 kg S ha-1. The highest number of open bolls per plant, seed cotton yield and boll weight were observed with the treatment consisting of 45 kg S ha-1 and 120 kg N ha-1. The seed cotton yield and boll weight tended to decrease as more N was applied however they were increased when N was applied with S. The N application had positive response on yield with S application and increasing N application in these situation positively affected on yield also. Joint effects of N and S on leaf nitrogen and sulfur content were found. It can be concluded that 120 to 180 kg ha-1 nitrogen and 45 to 60 kg ha-1 sulfur applications rates had better results than the rest of other N and S combinations. [ABSTRACT FROM AUTHOR]

Aim: The aim was to study the effects of two different cover crops (leguminous versus gramineous) on soil NO-N availability, grapevine N status, and yeast-assimilable N (YAN) and amino acid profile in the must of a cv. Tempranillo vineyard from La Rioja (Spain) over 3 years. Methods: Three treatments were established: gramineous (barley) and leguminous (Persian clover) cover crops and conventional tillage. Soil total N and extractable NH-N at bloom, soil NO-N content from budbreak to postharvest, leaf N content at bloom, and free amino acids and ammonia in must were monitored. Results: Each year, the barley cover crop treatment had lower soil NO-N than tillage, while the clover treatment showed lower soil NO-N than tillage in 2009 and showed higher values in 2010 and 2011. In 2011 leaf N content, yeast-assimilable N (YAN), and some amino acids in the grapes were lower in barley cover crop treatment thus affecting the amino acid profile. Meanwhile, the clover cover crop did not have these effects. Furthermore, relationships between leaf N content and various amino acids were also found. Conclusions: With the barley cover crop treatment, soil N availability decreased from the first year of the experiment, provoking a decrease in N grapevine status and in content of YAN and various amino acids at the third year. In contrast, clover cover crop maintained N grapevine status, YAN, and amino acid profile similar to conventional tillage. Therefore, our study shows how soil N can be managed both within a year and from year to year when two different cover crops are sown and how the grapevine N nutritional status and YAN content and amino acid profile can be modified in the must. [ABSTRACT FROM AUTHOR]

It is essential to understand the underlying physiological regulation of the effects of nitrogen fertilization to yield. Exploring the characteristics of flag leaf photosynthesis after the headed stage is of importance since the flag leaf assimilation product of this stage are the main sources of yield. In this research, winter wheat fields with sufficient drip irrigation and different nitrogen fertilization treatments were selected as the object of the study. Three nitrogen fertilization levels were designed. Net photosynthetic rate to photo active radiation (PAR) curves of different stages were measured with Li-cor 6400 portable photosynthesis system, to get the capacity of photosynthesis, i.e. the maximum photosynthetic rate (Amax) and the apparent quantum yield (α). The specific leaf mass (SLA), leaf nitrogen content per leaf mass (N-mass), leaf nitrogen content per leaf area (N-area) and 13C carbon isotope discrimination rate (Δ) were also determined by analyzing the leaf samples after photosynthesis measurements. Yield and water use efficiency were also estimated. The light curves were fit using a non-rectangular hyperbolic regression to obtain the relevant parameters for a comparison among treatments. Linear fitting was used for the light data at 0-150 μmol/(m2·s), the slope of the line was α and the intercept was the respiration rate (Rd). The results showed that the more nitrogen fertilization significantly increased the parameters of Amax and α (P=0.046), extended the duration of the better photosynthesis function, especially for the highest nitrogen treatments (N3, 221 kg/hm2). Rd and PARc showed no significant differences among treatments for the measurements on May 21st-23rd and June 2nd -3rd. The mean values of Rd of the three measurements were 1.54, 1.98 and 1.90 μmol/(m2·s), respectively. The Amax values gradually decreased over the duration of the field trial. The Amax of N3, N2 and N1 treatments on June 2nd-3rd were 14.0%, 28.9% and 39.9% lower than the Amax values measured on May 4th-5th, respectively. The Amax of the high N treatment, i.e. the N3 treatment, was kept fairly high even at the end of the milky stagy in the June 2-3 measurement. That's the reason of the highest yield of the N3 treatment. However, the evapotranspiration were not affected significantly by nitrogen treatments in this study. In this case, the water use efficiency of the N3 treatments was the highest. The yield of winter wheat for N3, N2 and N1 were 6646.5, 6 302.2 and 5810.2 kg/hm2, respectively. Y of N3 was 14.4% higher than that of N1 with significantly difference (P=0.046). The WUEa values of N3, N2 and N1 treatments were 14.34, 13.41 and 12.25 kg/(hm2·mm) respectively. The enhancement of Amax were related to the SLA, N-mass, N-area and Δ. Except that Amax was with marginally significant linear correlation with Δ (P=0.057) for N1 treatment, under all other treatments, there were significant linear relationships between Amax and SLA, Δ, N-mass and N-area. N treatments affected those relationships significantly. With the decreased N fertilization, absolute values of slopes of the regression lines were increased, suggesting that Amax is highly sensitive to the above parameters if lower N applied. In the relationships between Amax and leaf N content, the absolute value of Y-intercept of the N3 treatment was the highest and the slope was the lowest, suggesting that the Amax of N3 were higher at a given leaf N content, both at the mass and area basis. This may be interpreted as a result of changes in nitrogen partitioning in the photosynthetic apparatus. The results of this study explained the underlying photosynthetic regulation of yield enhancement by nitrogen fertilization in winter wheat fields. Moreover, the photosynthesis and leaf traits parameters determined in this study are readily to be used in some crop models to increase the accuracy of estimation under conditions of nitrogen treatments. [ABSTRACT FROM AUTHOR]

Downy mildew (caused by Plasmopara viticola) is a disease that strongly affect grapevine. To date, the use of fungicide is still the most effective way to prevent the spreading of the pathogen. However, concerns about the safety and the environmental impact of the fungicides make the search of new solutions an urgent problem. Nitrogen nutrition can be one of this. Indeed, P. viticola, that lack of some nitrogen related pathways, can take advantage of plant nitrogen. In this work, we hypothesized that P. viticola could suffer the absence of nitrogen, making the susceptible Pinot Noir cultivar less susceptible to the pathogen. Pinot noir plants were grown in hydroponic solutions with five different nitrogen concentrations (0, 0.05, 1, 2 and 5 mM) and leaf nitrogen content, photosynthetic performance, P. viticola sporulation and gene expression of four nitrogen-related genes (VvLBDIc3, VvLBDIf5, VvLBDIIa3 and VvLBDIIb2) were estimated at three different time points. Leaf nitrogen content, photosynthetic performance and disease severity were reduced at the 0 mM treatment. Nitrogen treatments modulated the expression of genes analysed. VvLBDIc3, VvLBDIf5 and VvLBDIIa3 were overexpressed at low nitrogen concentrations, suggesting a role during nitrogen starvation. While, VvLBDIIb2 was underexpressed at low nitrogen concentrations. A correlation between disease severity and gene espression has been highlighted. These data demonstrated that decrease in nitrogen content can have a positive impact on the incidence of downy mildew, stressing the importance to manage the vineyard nitrogen nutritional status and suggesting an appropriate use of fertilizers, with a beneficial impact for environment and human health. [ABSTRACT FROM AUTHOR]

Nitrogen is an essential nutrient element in crop photosynthesis and yield improvement. Thus, it is urgent and important to accurately estimate the leaf nitrogen contents (LNC) of crops for precision nitrogen management. Based on the correlation between LNC and reflectance spectra, the hyperspectral LiDAR (HSL) system can determine three-dimensional structural parameters and biochemical changes of crops. Thereby, HSL technology has been widely used to monitor the LNC of crops at leaf and canopy levels. In addition, the laser-induced fluorescence (LIF) of chlorophyll, related to the histological structure and physiological conditions of green plants, can also be utilized to detect nutrient stress in crops. In this study, four regression algorithms, support vector machines (SVMs), partial least squares (PLS) and two artificial neural networks (ANNs), back propagation NNs (BP-NNs) and radial basic function NNs (RBF-NNs), were selected to estimate rice LNC in booting and heading stages based on reflectance and LIF spectra. These four regression algorithms were used for 36 input variables, including the reflectance spectral variables on 32 wavelengths and four peaks of the LIF spectra. A feature weight algorithm was proposed to select different band combinations for the LNC retrieval models. The determination coefficient (R2) and the root mean square error (RMSE) of the retrieval models were utilized to compare their abilities of estimating the rice LNC. The experimental results demonstrate that (I) these four regression methods are useful for estimating rice LNC in the order of RBF-NNs > SVMs > BP-NNs > PLS; (II) The LIF data in two forms, including peaks and indices, display potential in rice LNC retrieval, especially when using the PLS regression (PLSR) model for the relationship of rice LNC with spectral variables. The feature weighting algorithm is an effective and necessary method to determine appropriate band combinations for rice LNC estimation.

Hyperspectral sensing techniques can be effective for rapid, non-destructive detecting of the nitrogen (N) status in crop plants; however, their accuracy is often affected by the soil background. Under different fractions of soil background, the canopy spectra and leaf nitrogen content (LNC) in winter wheat ( Triticum aestivum L.) were obtained from field experiments with different N rates and planting densities over 3 growing seasons. Five types of vegetation index (VIs: normalized difference vegetation index (NDVI), ratio vegetation index (RVI), soil adjusted vegetation index (SAVI), optimize soil adjusted vegetation index (OSAVI), and perpendicular vegetation index (PVI)) were constructed based on three types of spectral information: (1) the original and the first derivative (FD) spectrum, (2) the spectrum adjusted with the vegetation coverage (FV cover ), and (3) the pure spectrum extracted by a linear mixed model. Comprehensive relationships of above five types of VI with LNC were quantified for LNC detecting under different soil backgrounds. The results indicated that all five types of VI were significantly affected by the soil background, with R 2 values of around 0.55 for LNC detecting, with the OSAVI ( R 514 , R 469 ) L =0.04 producing the best performance of all five indices. However, based on the FV cover , the coverage adjusted spectral index (CASI = NDVI( R 513 , R 481 )/(1 + FV cover )) produced the higher R 2 value of 0.62 and the lower RRMSE of 13%, and was less sensitive to the leaf area index (LAI), leaf dry weight (LDW), FV cover , and leaf nitrogen accumulation (LNA). The results demonstrate that the newly developed CASI could improve the performance of LNC estimation under different soil backgrounds. [ABSTRACT FROM AUTHOR]

In a global context,increasing of nitrogen and phosphorus are affecting the ecosystem biogeochemical cycles,which may have an impact on nutrient retention properties of plants. We studied the potential effects of nutrients additions on foliar nutrient and photosynthetic traits of Potentilla fruiticosa in a sub-alpine meadow,and the relationships between these leaf traits. The treatments involved additions of 5,10 and 15 g·m-2 nitrogen(N),phosphorus(P)alone and combined,respectively,and a control(no nutrient added). The results showed,at the treatment level,N or P addition alone increased N:P ratio(N:P)significantly of P. fruiticosa,but nutrients addition treatments had no significant effect on foliar nitrogen content(Nmass),phosphorus content(Pmass),leaf mass per area(LMA),net photosynthetic rate(Pn)and photosynthetic nitrogen use efficiency(PNUE). Nutrient levels had significant effect on foliar Nmass,N:P,Pn and PNUE in each treatment,except Pmass and LMA in P addition alone,and there was a decreasing but insignificant trend of LMA with increasing nutrients levels. Across the study,the Nmass was positively correlated with the Pmass(R2=0.347,P<0.001)and the N:P(R2=0.018,P<0.05),while the Pmass was significantly negatively correlated with the N:P(R2=0.505,P<0.001). The LMA had a significantly negative relationship with the Pn(R2=0.02,P<0.05),but a significantly positively one with the PNUE(R2=0.077,P<0.001). In general,these results suggested moderate environmental change would change nutrient retention,photosynthetic capacity and nutritional use strategy of P. fruiticosa. [ABSTRACT FROM AUTHOR]

Assessing family- and species-level variation in physiological responses to global change across geologic time is critical for understanding factors that underlie changes in species distributions and community composition. Here, we used stable carbon isotopes, leaf nitrogen content and stomatal measurements to assess changes in leaf-level physiology in a mixed conifer community that underwent significant changes in composition since the last glacial maximum (LGM) (21 kyr BP). Our results indicate that most plant taxa decreased stomatal conductance and/or maximum photosynthetic capacity in response to changing conditions since the LGM. However, plant families and species differed in the timing and magnitude of these physiological responses, and responses were more similar within families than within co-occurring species assemblages. This suggests that adaptation at the level of leaf physiology may not be the main determinant of shifts in community composition, and that plant evolutionary history may drive physiological adaptation to global change over recent geologic time. [ABSTRACT FROM AUTHOR]

Increases in rates of individual leaf photosynthesis (P n) are critical for future increases of rice yields. A previous study, using introgression lines derived from a cross between indica cultivar Habataki, with one of the highest recorded values of P n, and the Japanese elite cultivar Koshihikari, identified four QTLs (qCAR4, qCAR5, qCAR8, and qCAR11) that affect P n. The present study examined the combined effect of qCAR4 and qCAR8 on P n in the genetic background of Koshihikari. The pyramided near-isogenic line NIL(qCAR4+qCAR8) showed higher P n than both NIL(qCAR4) and NIL(qCAR8), equivalent to that of Habataki despite being due to only two out of the four QTLs. The high P n of NIL(qCAR4+qCAR8) may be attributable to the high leaf nitrogen content, which may have been inherited from NIL(qCAR4), to the large hydraulic conductance due to the large root surface area from NIL(qCAR4), and to the high hydraulic conductivity from NIL(qCAR8). It might be also attributable to high mesophyll conductance, which may have been inherited from NIL(qCAR4). The induction of mesophyll conductance and the high leaf nitrogen content and high hydraulic conductivity could not be explained in isolation from the Koshihikari background. These results suggest that QTL pyramiding is a useful approach in rice breeding aimed at increasing P n. [ABSTRACT FROM PUBLISHER]

Leaf nitrogen concentration (LNC) is a critical indicator of crop nutrient status. In this study, the feasibility of using visible and near-infrared spectroscopy combined with deep learning to estimate LNC in cotton leaves was explored. The samples were collected from cotton's whole growth cycle, and the spectra were from different measurement environments. The random frog (RF), weighted partial least squares regression (WPLS), and saliency map were used for characteristic wavelength selection. Qualitative models (partial least squares discriminant analysis (PLS-DA), support vector machine for classification (SVC), convolutional neural network classification (CNNC) and quantitative models (partial least squares regression (PLSR), support vector machine for regression (SVR), convolutional neural network regression (CNNR)) were established based on the full spectra and characteristic wavelengths. Satisfactory results were obtained by models based on CNN. The classification accuracy of leaves in three different LNC ranges was up to 83.34%, and the root mean square error of prediction (RMSEP) of quantitative prediction models of cotton leaves was as low as 3.36. In addition, the identification of cotton leaves based on the predicted LNC also achieved good results. These results indicated that the nitrogen content of cotton leaves could be effectively detected by deep learning and visible and near-infrared spectroscopy, which has great potential for real-world application., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Xiao, Wu, Tang, Zhang, Feng, Zhou, Shen, Zhang, Gao and He.)

Background: The nitrogen (N) and protein concentrations in plant tissues exposed to elevated CO 2 (eCO 2 ) generally decline , such declines in forage grass composition are expected to have negative implications for the nutritional and economic value of grass. Plants require N for the production of a photosynthetically active canopy and storage proteins in the tissues, whose functionality will strongly influence productivity and quality. The objective of this study was to investigate whether eCO 2 plus N-fertilization increases growth and N nutrition of Agropyron mongolicum , and the dependence of this improvement on the coordination between root and leaf development., Methods: We analyzed A. mongolicum from field-grown within the open-top chambers (OTCs) facility under two atmospheric CO 2 (ambient, 400 ± 20 µmol mol -1 , aCO 2 , and elevated, 800 ± 20 µmol mol -1 , eCO 2 ) and three N-fertigation treatments (control, low N-fertigation , and high N-fertigation) for two months., Results: Elevated CO 2 plus N-fertigation strongly increased shoot and root biomass, and the nitrogen and protein concentrations of A. mongolicum compared to those plants at aCO 2 levels. Increased N content in leaves and reduced specific leaf area (SLA) at a high N supply could alleviate photosynthetic acclimation to eCO 2 and drive the production of greater shoot biomass with the potential for higher photosynthesis, productivity, and nutritional quality. The increased root length (RL), the ratio of total aboveground N taken up per RL (TN/RL), stomatal conductance (Gs), and transpiration rate (Tr) contribute to the transpiration-driven mass flow of N, consequently increasing N uptake by roots. In addition, a smaller percentage of N remained as unassimilated nitrate ( NO 3 - ) under eCO 2 , indicating that assimilation of NO 3 - into proteins was not inhibited by eCO 2 . These findings imply that grass productivity and quality will enhance under anticipated elevated CO 2 concentration when effective management measures of N-fertilization are employed., Competing Interests: The authors declare there are no competing interests., (©2022 Xu et al.)