Photosynthetic Nitrogen Use Research Articles

Low foliar construction cost and strong investment in root biomass in Calotropis procera, an invasive species under drought and recovery

The relationship between uptake and use of resources has always been highlighted among functional traits to explain the performance of invasive and native species. However, previous studies have shown that, under resource limitation, the species of both groups tend to have similar functional behavior. We measured a group of resource-use traits under controlled drought stress in Cenostigma microphyllum native to Caatinga of Brazil and the invasive species Calotropis procera that has a large occurrence in semiarid regions. The results showed that invasive well-watered plants always had higher CO2 assimilation rates and lower leaf construction costs than native plants, while stomatal conductance was similar. On the other hand, under water deficit conditions, the invasive plants tolerated more days of drought and showed higher root/shoot biomass ratio, leaf relative water content, lower leaf construction costs and payback time than the native species. Moreover, seven days after stress, the invasive plants displayed higher CO2 assimilation, photosynthetic nitrogen use efficiency, instantaneous efficiency of energy use and lower leaf construction costs compared with the native species. The ability to acquire and distribute resources among the different plant tissues at the right time seems to be a fundamental combination for the plants used in the experiment. Thus, a more acquisitive strategy is fundamental for having enough carbon to invest in the root biomass in C. procera under drought, which could contribute to maintain higher leaf water status for longer time compared with C. microphyllum.

Silicon dioxide nanofertilizers improve photosynthetic capacity of two Criollo cocoa clones (Theobroma cacao L.)

SummaryStudies on the effect of nanofertilizers (NF) in physiological performance of plants is scarce, especially that related to substances encapsulated into silicon dioxide (SiO2) nanoparticles in cocoa plants. The effect of foliar application of SiO2-NF on nutrient contents, gas exchange, photochemical activity, photosynthetic pigments, total soluble protein (TSP), photosynthetic nitrogen use efficiency (PNUE), and growth in seedlings of two cocoa clones (OC-61 and BR-05) in a greenhouse was assessed. Spraying with SiO2-NF increased net photosynthetic rate (A) by 16 and 60% and electron transport rate (J) by 52 and 162% in clones OC-61 and BR-05, respectively, without changes in photosynthetic pigment concentration in either clone. The SiO2-NF caused a decrease of 37 and 22% in stomatal conductance in OC-61 and BR-05, respectively; a similar trend was observed in transpiration rate, causing an increase of 42 and 100% in water use efficiency in OC-61 and BR-05, respectively. In both clones, diameter of graft increased on average 28% with SiO2-NF. Higher photosynthetic capacity was related to an increase in leaf N, P, and TSP. A significant reduction in PNUE (A/N ratio) was found in OC-61, whereas in BR-05 PNUE increased after spraying with SiO2-NF. Overall, spraying with SiO2-NF had a positive effect on photosynthetic processes in both cocoa clones, associated with an increase in nutrients content, which translated into improved growth. A differential physiological response to spraying with SiO2-NF between clones was also found, with BR-05 being the clone with a better physiological response during the establishment and development stages.

Changes in Leaf-Level Nitrogen Partitioning and Mesophyll Conductance Deliver Increased Photosynthesis for Lolium perenne Leaves Engineered to Accumulate Lipid Carbon Sinks.

Diacylglycerol acyl-transferase (DGAT) and cysteine oleosin (CO) expression confers a novel carbon sink (of encapsulated lipid droplets) in leaves of Lolium perenne and has been shown to increase photosynthesis and biomass. However, the physiological mechanism by which DGAT + CO increases photosynthesis remains unresolved. To evaluate the relationship between sink strength and photosynthesis, we examined fatty acids (FA), water-soluble carbohydrates (WSC), gas exchange parameters and leaf nitrogen for multiple DGAT + CO lines varying in transgene accumulation. To identify the physiological traits which deliver increased photosynthesis, we assessed two important determinants of photosynthetic efficiency, CO2 conductance from atmosphere to chloroplast, and nitrogen partitioning between different photosynthetic and non-photosynthetic pools. We found that DGAT + CO accumulation increased FA at the expense of WSC in leaves of L. perenne and for those lines with a significant reduction in WSC, we also observed an increase in photosynthesis and photosynthetic nitrogen use efficiency. DGAT + CO L. perenne displayed no change in rubisco content or Vcmax but did exhibit a significant increase in specific leaf area (SLA), stomatal and mesophyll conductance, and leaf nitrogen allocated to photosynthetic electron transport. Collectively, we showed that increased carbon demand via DGAT+CO lipid sink accumulation can induce leaf-level changes in L. perenne which deliver increased rates of photosynthesis and growth. Carbon sinks engineered within photosynthetic cells provide a promising new strategy for increasing photosynthesis and crop productivity.

Effects of water-nitrogen coupling on photosynthetic characteristics, yield, water and nitrogen use efficiency for mountain apple trees under surge-root irrigation in Northern Shaanxi area of China.

Taking 7-year-old apple trees (Hanfu) as the test material, an experiment with three irrigation levels including high water (W1, 85%-100%θf, θf was the field water holding capacity), medium water (W2, 70%-85%θf) and low water (W3, 55%-70%θf), and three nitrogen application levels, high (N1, 600 kg·hm-2), medium (N2, 400 kg·hm-2) and low (N3, 200 kg·hm-2), was conducted to investigate the effects of water and nitrogen coupling on photosynthetic characteristics, yield and water and nitrogen utilization of apple trees in mountainous areas under surge-root irrigation (SRI). The results showed that the net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (gs), intercellular CO2 concentration (Ci), leaf instantaneous water use efficiency (WUEi) of apple trees leaves decreased with decreasing nitrogen application rates under the same irrigation amount, but Ci increased. Under the same nitrogen application rate, foliar Pn, Tr, gs and WUEi decreased with decreasing irrigation amount, but Ci increased. The daily average values of Pn and Tr under W1N1 treatment were the largest, while W2N2 treatment had the largest WUEi. Apple yield, irrigation water use efficiency (IWUE) and nitrogen partial productivity (NPFP) were significantly affected by irrigation and nitrogen application. The W2N2 treatment had the highest yield (26761 kg·hm-2). IWUE increased significantly with the decreasing irrigation and the increasing nitrogen application, while NPFP increased significantly with the increases of irrigation and the decreases of nitrogen application. Results of the regression analysis showed that the combination of irrigation and nitrogen application was closest to W2N2 treatment when yield and IWUE got the optimal solution. Therefore, W2N2 treatment was the best combination mode of water and nitrogen application for apple under SRI in Northern Shaanxi mountain area.

Nitric Oxide Enhances Photosynthetic Nitrogen and Sulfur-Use Efficiency and Activity of Ascorbate-Glutathione Cycle to Reduce High Temperature Stress-Induced Oxidative Stress in Rice (Oryza sativa L.) Plants.

The effects of nitric oxide (NO) as 100 µM sodium nitroprusside (SNP, NO donor) on photosynthetic-nitrogen use efficiency (NUE), photosynthetic-sulfur use efficiency (SUE), photosynthesis, growth and agronomic traits of rice (Oryza sativa L.) cultivars, Taipie-309 (high photosynthetic-N and SUE) and Rasi (low photosynthetic-N and SUE) were investigated under high temperature stress (40 °C for 6 h). Plants exposed to high temperature stress caused significant reduction in photosynthetic activity, use efficiency of N and S, and increment in H2O2 and thiobarbituric acid reactive substance (TBARS) content. The drastic effects of high temperature stress were more pronounced in cultivar Rasi than Taipie-309. However, foliar spray of SNP decreased the high temperature induced H2O2 and TBARS content and increased accumulation of proline and activity of ascorbate–glutathione cycle that collectively improved tolerance to high temperature stress more effectively in Taipie-309. Exogenously applied SNP alleviated the high temperature induced decrease in photosynthesis through maintaining higher photosynthetic-NUE and photosynthetic-SUE, activity of ribulose 1,5 bisphosphate carboxylase/oxygenase (Rubisco), and synthesis of reduced glutathione (GSH). The use of 2-4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxy-3-oxide (cPTIO, NO scavenger) substantiated the study that in the absence of NO oxidative stress increased, while NO increased photosynthetic-NUE and photosynthetic-SUE, net photosynthesis and plant dry mass. Taken together, the present investigation reveals that NO increased heat stress tolerance and minimized high temperature stress adversaries more effectively in cultivar Taipie-309 than Rasi by enhancing photosynthetic-NUE and SUE and strengthening the antioxidant defense system.

Anatomically induced changes in rice leaf mesophyll conductance explain the variation in photosynthetic nitrogen use efficiency under contrasting nitrogen supply

BackgroundThe ratio of CO2 mesophyll conductance (gm) to Ribulose-1, 5-bisphosphate carboxylase/oxygenase (Rubisco) content has been suggested to positively affect photosynthetic nitrogen use efficiency (PNUE). The anatomical basis of gm has been quantified, but information on the relationship between cell-level anatomies and PNUE is less advanced. Here, hydroponic experiments were conducted in rice plants supplied with ammonium (NH4+) and nitrate (NO3−) under three N levels (low, 0.71 mM; intermediate, 2.86 mM; high, 7.14 mM) to investigate the gas exchange parameters, leaf anatomical structure and PNUE.ResultsThe results showed a lower PNUE in plants supplied with high nitrogen and NH4+, which was positively correlated with the gm/Rubisco ratio. A one-dimensional within-leaf model revealed that the resistance to CO2 diffusion in the liquid phase (rliq) dominated the overall mesophyll resistance (rm), in which CO2 transfer resistance in the cell wall, cytoplasm and stroma were significantly affected by nitrogen supply. The chloroplast surface area exposed to intercellular space (Sc) per Rubisco rather than the gm/Sc ratio was positively correlated with PNUE and was thus considered a key component influencing PNUE.ConclusionIn conclusion, our study emphasized that Sc was the most important anatomical trait in coordinating gm and PNUE with contrasting N supply.

Overlapping Water and Nutrient Use Efficiencies and Carbon Assimilation between Coexisting Simple- and Compound-Leaved Trees from a Valley Savanna

Identifying differences in ecophysiology between simple and compound leaves can help understand the adaptive significance of the compound leaf form and its response to climate change. However, we still know surprisingly little about differences in water and nutrient use, and photosynthetic capacity between co-occurring compound-leaved and simple-leaved tree species, especially in savanna ecosystems with dry-hot climate conditions. From July to September in 2015, we investigated 16 functional traits associated with water use, nutrients, and photosynthesis of six deciduous tree species (three simple-leaved and three compound-leaved species) coexisting in a valley-savanna in Southwest China. Our major objective was to test the variation in these functional traits between these two leaf forms. Overall, overlapping leaf mass per area (LMA), photosynthesis, as well as leaf nitrogen and phosphorus concentrations were found between these coexisting valley-savanna simple- and compound-leaved tree species. We didn’t find significant differences in water and photosynthetic nitrogen or phosphorus use efficiency between simple and compound leaves. Across these simple- and compound-leaved tree species, photosynthetic phosphorus use efficiencies were positively related to LMA and negatively correlated with phosphorus concentration per mass or area. Water use efficiency (intrinsic water use efficiency or stable carbon isotopic composition) was independent of all leaf traits. Similar ecophysiology strategies among these coexisting valley-savanna simple- and compound-leaved species suggested a convergence in ecological adaptation to the hot and dry environment. The overlap in traits related to water use, carbon assimilation, and stress tolerance (e.g., LMA) also suggests a similar response of these two leaf forms to a hotter and drier future due to the climate change.

Estimation of leaf nitrogen content and photosynthetic nitrogen use efficiency in wheat using sun-induced chlorophyll fluorescence at the leaf and canopy scales

Leaf nitrogen content (LNC), an indicator for the amount of photosynthetic proteins, plays an important role to understand plant function and status. In previous studies, vegetation indices (VIs) have been demonstrated to monitor LNC non-destructively, but which is influenced by backgrounds, and lacks specificity for nitrogen stress. In this study, sun-induced chlorophyll fluorescence (SIF), a novel technique related to plant physiology state, was proposed to estimate area-based and mass-based LNC at both leaf and canopy scales. In addition, SIF indices were evaluated to retrieve photosynthesis nitrogen use efficiency (PNUE), an important trait of leaf economics and physiology, based on the relationships between SIF, photosynthesis, and LNC.This study was conducted on two field experiments of winter wheat with different nitrogen regimes in Rugao, Jiangsu Province, China during 2016-2017 and 2017-2018 growing seasons. We took measurements of SIF, reflectance, biochemical and growth structural parameters at the leaf and canopy scales. The SIF signal was collected using ASD (Analytical Spectral Devices, Boulder, CO, USA) and QEpro (Ocean Optics, Dunedin, FL, USA) spectrometers at the two observational scales, with a full width at half maximum (FWHM) of 1.4 nm and 0.13 nm, respectively. SIF indices were calculated based on the SIF signal extracted at two oxygen absorption bands. Our results demonstrated that area-based LNC was better related to SIF indices and VIs than mass-based LNC. SIF ratio index (SIFR) and normalized SIF index (SIFN), defined as SIF761/SIF687 and (SIF761-SIF687)/(SIF761+SIF687) separately, performed better in monitoring area-based LNC at the two observation scales than CIred edge, which performed best in VIs group. Compared with CIred edge, the best estimation accuracy of SIF indices for area-based LNC increased by 0.08 and 0.02 at the leaf and canopy scales, separately. And when using SIFR and SIFN to monitor area-based LNC, there is no saturation phenomenon, which occurs using traditional VIs. From the whole range of data, area-based LNC was closely related to several plant traits (leaf: area-based leaf chlorophyll content (LCC) (LCCarea), leaf mass per area (LMA); canopy: area-based canopy LCC (CCCarea), leaf area index (LAI), leaf dry weight (LDW) per unit soil area, and LMA), which was consistent with previous studies. However, in specific group with fixed area-based LCC value, although area-based LNC almost wasn’t significantly correlated with these traits, SIFR and SIFN were instead always highly correlated with area-based LNC in each small datasets on two observation scales (leaf scale: R2>0.50, R2>0.46; canopy scale: R2>0.41, R2>0.42). Thus, the contribution of SIFR and SIFN to estimate area-based LNC wasn’t only the plant traits listed, but also other internal characters, like nitrogen allocation and proportion. Moreover, SIFR and SIFN were proved to be potential detectors to retrieve PNUE. These findings would provide us a new perspective for understanding plant nitrogen status from remote sensing observations, detecting plant function and managing precise agriculture.

Differences in carbon and nitrogen metabolism between male and female Populus cathayana in response to deficient nitrogen.

Sexual dimorphism occurs regarding carbon and nitrogen metabolic processes in response to nitrogen supply. Differences in fixation and remobilization of carbon and allocation and assimilation of nitrogen between sexes may differ under severe defoliation. The dioecious species Populus cathayana was studied after two defoliation treatments with two N levels. Males had a higher capacity of carbon fixation because of higher gas exchange and fluorescence traits of leaves after severe long-term defoliation under deficient N. Males had higher leaf abscisic acid, stomatal conductance and leaf sucrose phosphate synthase activity increasing transport of sucrose to sinks. Males had a higher carbon sink than females, because under N-deficient conditions, males accumulated >131.10% and 90.65% root starch than males in the control, whereas females accumulated >40.55% and 52.81%, respectively, than females in the control group. Males allocated less non-protein N (NNon-p) to leaves, having higher nitrogen use efficiency (photosynthetic nitrogen use efficiency), higher glutamate dehydrogenase (GDH) and higher leaf GDH expression, even after long-term severe defoliation under deficient N. Females had higher leaf jasmonic acid concentration and NNon-p. The present study suggested that females allocated more carbon and nitrogen to defense chemicals than males after long-term severe defoliation under deficient N.

Comparisons of irradiance utilization efficiency by invasive Chromolaena odorata and its three co-occurring species in one planted understory

High irradiance utilization efficiency is one important character for some invasive plants. Chromolaena odorata is one noxious invasive species originating from Latin America, which had spread widely in most tropical and subtropical areas. To explore why C. odorata perform better than native plants in the understory of planted forests, we compared the irradiance utilization efficiency between invasive C. odorata and three co-occurring species (Merremia vitifolia, Pueraria phaseoloides, and Litsea monopetala). We found that C. odorata had lower leaf thickness but higher specific leaf area, net photosynthetic rate per leaf thickness and photosynthetic nitrogen use efficiency than the three native species. The photosynthetic resistance to irradiance damage was stronger for C. odorata than for the three native species. These traits may have contributed to the higher performance of C. odorata than native plants, which may in turn facilitate its invasion in the understory.

Competitive ability and plasticity of Wedelia trilobata (L.) under wetland hydrological variations

Growth behavior of different species under different habitats can be studied by comparing the production of biomass, plasticity index and relative competitive interaction. However, these functional traits of invasive species received rare consideration for determining the invasion success of invasive species at wetlands. Here, we examined the effect of water depth at 5 cm and 15 cm (static and fluctuated) with different nutrient concentrations (full-strength (n1), 1/4-strength (n2) and 1/8-strength (n3) Hoagland solution) on functional traits of invasive Wedelia trilobata and its congener native Wedelia chinensis under mono and mixed culture. Water depth of 5 cm with any of the nutrient treatments (n1, n2 and n3) significantly restrained the photosynthesis, leaf nitrogen and photosynthetic nitrogen use efficiency (PNUE) of both W. trilobata and W. chinensis. While, increase in the water depth to 15 cm with low nutrient treatment (n3) reduced more of biomass of W. chinensis under mixed culture. However, relative competition interaction (RCI) was recorded positive for W. trilobata and seemingly W. trilobata benefited more from RCI under high-fluctuated water depth at 15 cm in mixed culture. Therefore, higher PNUE, more competitive ability and higher plasticity may contribute to the invasiveness of W. trilobata in wetlands.

Nitrogen Use Efficiency for Growth of Fagus crenata Seedlings Under Elevated Ozone and Different Soil Nutrient Conditions

Ozone is a phytotoxic gaseous air pollutant and its negative effects on forest production are a major concern. To understand the effects of ozone on forest production, it is important to clarify the nitrogen use efficiency (NUE) for tree growth under elevated ozone conditions, because nitrogen is a primal limiting factor of forest production in many cool-temperate forests. Soil nutrient conditions are considered factors affecting ozone susceptibility of tree growth. Therefore, in the present study, we investigated the effects of ozone on NUE for the growth of Siebold’s beech (Fagus crenata Blume) seedlings grown under different soil nutrient conditions. Seedlings of Siebold’s beech were grown under three gas treatments (charcoal-filtered air or ozone at 1.0 or 1.5 times the ambient concentration) in combination with three soil nutrient conditions (non-fertilised, low-fertilised or high-fertilised) for two growing seasons. Based on the dry mass and nitrogen concentration in each plant organ, we calculated NUE and its components, including nitrogen productivity (NP) and the mean residence time of nitrogen (MRT) during the second growing season. Ozone did not decrease the NUE of the seedlings during the second growing season, whereas leaf level photosynthetic nitrogen use efficiency (PNUE), a component of NP, was decreased by ozone. On the other hand, the soil nutrient supply decreased the NUE of the seedlings. Reductions in both NP and MRT were attributed to the decrease in NUE because of soil nutrient supply, whereas PNUE did not respond to soil nutrient supply. There was no significant interaction of ozone and soil nutrient supply on the NUE, or its components, of the seedlings. Our results indicated that there is a difference in the response between the NUE for individual growth and that of leaf level PNUE of Siebold’s beech seedlings to ozone and soil nutrient supply.

Responses of an old and a modern Indian wheat cultivar to future O3 level: Physiological, yield and grain quality parameters

A field study was conducted to understand the physiological responses, yield and grain quality of an old (HUW234) and a modern (HD3118) wheat cultivar exposed to elevated ozone (O3). The cultivars were grown under ambient O3 (NF) and ambient +20 ppb O3 (NF+) conditions using open-top chambers (OTCs). The comparative study of an old and a modern cultivar showed variable physiological responses under elevated O3 exposure. Elevated O3 in old cultivar caused high reductions in Rubisco activity (Vcmax) and electron transport rate (J) compared to modern cultivar with simultaneous reductions in the rate of photosynthesis and chlorophyll fluorescence. In modern cultivar, high stomatal density and conductance caused higher O3 uptake thereby triggering more damage to the adjacent stomatal cells and photosynthetic pigments coupled with reductions in photosynthetic rate and photosynthetic nitrogen use efficiency (PNUE). Modern cultivar also showed relatively high reduction in grain yield compared to old one under NF + treatment. Furthermore, grain quality traits (such as starch, protein and amino acids) of modern cultivar were better than old cultivar under ambient O3, but showed more deterioration under NF + treatment. Results thus indicated that modern cultivar is relatively more susceptible to O3 and showed more negative impacts on plant performance, yield and quality of grains compared to old cultivar.

干旱胁迫对群众杨光合特性与器官干物质分配的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 干旱胁迫对群众杨光合特性与器官干物质分配的影响 DOI: 10.5846/stxb201901270203 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31400527，31700534）；山西省应用基础研究项目（201701D221190）；山西农业大学引进人才博士科研启动项目（2013YJ18） Effects of water stress on leaf gas exchange and biomass allocation of Populus×popularis ‘35-44’ cuttings Author: Affiliation: Fund Project: National Natural Science Foundation of China (NSFC)、Shanxi applied basic research project、Shanxi agricultural university introduction of doctoral research projects 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:土壤干旱是北方地区杨树人工林生长和生态效益的重要限制因子。以群众杨（Populus×popularis'35-44’）扦插苗为研究材料，采用盆栽称重法控制土壤水分，设置正常供水、中度干旱、重度干旱3种水分梯度。分别于2016年9月与2017年9月测定叶片气体交换参数、各器官干重、根冠比、叶经济性状等指标，研究了持续2年干旱胁迫下群众杨扦插苗光合特性与器官干物质分配的变化规律，分析了土壤干旱程度、树龄在"小老树"形成中的作用过程。2016年与2017年中度、重度干旱胁迫下功能叶净光合速率（Pn）受到非气孔限制，与正常供水相比分别降低了36.08%、56.42%；18.47%、5.13%。第一年干旱胁迫下群众杨气孔导度（Gs）和蒸腾速率（Tr）显著降低；第二年干旱胁迫下Gs与正常供水无显著差异，而Tr显著提高，有利于叶片C、N元素的运输分配进而维持较高的Pn。第一年随干旱胁迫程度加剧，群众杨叶片C/N显著提高，光合产物分配趋向于叶器官。第二年中度干旱胁迫下叶片C/N与正常供水相比无显著差异，各器官干重下降幅度均低于2016年，而根冠比显著增加，表明其光合产物主要用于地下部构建以适应中度干旱环境；持续重度干旱则光合产物向茎中的分配比例提高。干旱胁迫导致群众杨功能叶水分利用效率（WUE，Water use efficiency）与光合氮利用效率（PNUE，Photosynthetic nitrogen use efficiency）显著降低，整株氮利用效率（NUE，Whole plant nitrogen use efficiency）显著提高。严重土壤干旱下叶片耗水增强、PNUE下降以及茎木质部碳投资增加可能是群众杨小老树形成的重要原因。 Abstract:Soil water content is a key limiting factor to development and ecological function of artificial poplar plantations in semi-arid area of northern China. To examine the effects of soil drought on a poplar variety Populus×popularis ‘35-44’, 3 soil water levels, i.e., normal (75%±5% of field capacity), moderate drought (50%±5%) and severe drought (25%±5%), were set up using 1 year old cutting seedlings grown in pots. We measured leaf gas exchange parameters, organ dry mass and leaf economic traits both in September 2016 and September 2017 to analyze interannual changes in leaf gas exchange and biomass allocation in an attempt to elucidate the effects of soil water stress and ageing in formation of the "old dwarf trees" phenomenon. Compared with seedlings grown at the normal soil water level, leaf net photosynthetic rates (Pn) of seedlings grown at moderate and severe soil drought levels were reduced by 36.08% and 56.42% in 2016 respectively and also 18.47% and 5.13% in 2017 respectively, mainly due to non-stoma limitation. In first year of soil water drought treatment, stomatal conductance (Gs) and transpiration rate (Tr) of seedlings grown at both soil drought levels decreased significantly. However, no significant decrease of Gs at both soil drought levels were found in second year, while Tr increased at both drought levels significantly, which could be beneficial to transportation of C and N to leaves and therefore maintenance of Pn. In first year of treatment, with increasing severity of soil drought, leaf C/N ratio increased significantly and more biomass was allocated to foliage. However, no significant differences were found in leaf C/N ratio between normal soil water level and moderate soil drought level in second year of treatment, while the decreases of all component biomass at moderate soil drought level in 2017 were less than those in 2016 with a significantly higher root-shoot ratio, indicating that more dry matter were allocated to underground for root construction in acclimation to moderate soil drought. In comparison, more dry matter were allocated to stem at severe soil drought level. After two years of soil drought treatment, water use efficiency (WUE) and photosynthetic nitrogen use efficiency (PNUE) of functional leaves of seedlings decreased significantly, but nitrogen use efficiency at whole plant level (NUE) increased significantly. Increased leaf water consumption, decreased PNUE and increased stem xylem C input of Populus×popularis ‘35-44’ seedlings at severe soil drought level may be the main drivers of "old dwarf trees" phenomenon. 参考文献 相似文献 引证文献

Experiments for in silico evaluation of Optimality of Photosynthetic Nitrogen Distribution and Partitioning in the Canopy: an Example Using Greenhouse Cucumber Plants.

Acclimation of leaf traits to fluctuating environments is a key mechanism to maximize fitness. One of the most important strategies in acclimation to changing light is to maintain efficient utilization of nitrogen in the photosynthetic apparatus by continuous modifications of between-leaf distribution along the canopy depth and within-leaf partitioning between photosynthetic functions according to local light availability. Between-leaf nitrogen distribution has been intensively studied over the last three decades, where proportional coordination between nitrogen concentration and light gradient was considered optimal in terms of maximizing canopy photosynthesis, without taking other canopy structural and physiological factors into account. We proposed a mechanistic model of protein turnover dynamics in different photosynthetic functions, which can be parameterized using leaves grown under different levels of constant light. By integrating this dynamic model into a multi-layer canopy model, constructed using data collected from a greenhouse experiment, it allowed us to test in silico the degree of optimality in photosynthetic nitrogen use for maximizing canopy carbon assimilation under given light environments.

Physiological Basis of Heterosis for Nitrogen Use Efficiency of Maize

Efficient use of nitrogen inputs for concurrent improvements in grain yield and nitrogen use efficiency (NUE) has been recognized as a viable strategy for sustainable agriculture development. Yet, there is little research on the possible physiological basis of maize hybrid heterosis for NUE and measurable traits that are corresponding to the NUE heterosis. A field study was conducted for two years to evaluate the heterosis for NUE and determine the relationship between NUE and its physiological components. Two commercial hybrids, ‘Xianyu335’ and ‘Zhengdan958’, and their parental inbred lines, were grown at 0 (0 N) and 150 kg N ha−1 (150 N), in a randomized complete block design with four replications each year. Compared to their parental lines, both hybrids displayed a significant heterosis, up to 466%, for NUE. N internal efficiency (NIE) accounted for 52% of the variation in heterosis for NUE, while there was generally negligible heterosis for nitrogen recovery efficiency (NRE). Heterosis for NIE and thereby for NUE in maize was ascribed to (i) an earlier establishment of pre-anthesis source for N accumulation, which phenotypically exhibited as a faster leaf appearance rate with higher maximum LAI and photosynthetic nitrogen use efficiency; (ii) a larger amount of N being remobilized from the vegetative tissues, especially from leaves, during the grain filling. Phenotypically, there was notably a rapid reduction in post-anthesis specific weights of leaf and stalk, but with maintained functionally stay-green ear leaves; and (iii) a higher productive efficiency per unit grain N, which was characterized by a reduced grain N concentration and enhanced sink strength.

Ecological variations of woody species along an altitudinal gradient in the Qinling Mountains of Central China: area-based versus mass-based expression of leaf traits

Leaf trait-based research has become the preferred method to understand the ecological strategies of plants. However, there is still a debate on whether area-based or mass-based traits provide different insights into environmental adaptations and responses. In this study, seven key leaf traits (maximum net photosynthetic rate, dark respiration rate, nitrogen content, photosynthetic nitrogen use efficiency, leaf mass per area, leaf dry matter contents and leaf area) of 43 woody species were quantified on the basis of both area and mass along an altitudinal gradient (1100–2700 m) in the Qinling Mountains of China. Differences in leaf traits and bivariate correlations between the two expressions were compared. By considering different expressions, the strengths and directions of the responses of leaf traits to the altitudinal gradient were determined. Leaf traits showed large variations; interspecific variations contributed more to total variance than intraspecific variations. Bivariate correlations between photosynthetic traits and structural traits (mass per area, dry matter content, and area) were weaker on a mass basis than those on an area basis. Most traits exhibited quadratic trends along the altitudinal gradient, and these patterns were more noticeable for area-based than mass-based traits. Area-based traits were more sensitive to changes in temperature and precipitation associated with altitude. These results provide evidence that mass- versus area-based traits show different ecological responses to environmental conditions associated with altitude, even if they do not contain very broad spatial scales. Our results also indicate distinction of photosynthetic acclimation among the two expressions along an altitudinal gradient, reflecting trade-offs among leaf structure and physiological traits.

Ecophysiological traits of invasive alien Acacia cyclops compared to co‐occuring native species in Strandveld vegetation of the Cape Floristic Region

AbstractTree invasions of Mediterranean‐climate ecosystems pose a significant threat to both biodiversity and functioning, by excluding native species, altering soil nutrient status and depleting water resources. In order to attain greater relative biomass associated with successful invasion in these characteristically resource‐poor environments, invasive species must have novel traits that enable better acquisition (e.g. deep roots) or exploitation of different resources (e.g. N2 fixation) and/or more efficient use of available resources than native species. We compared the ecophysiological and morphological traits of three abundant native species to those of the invasive Australian tree species, Acacia cyclops. This species is widely invasive in the Mediterranean‐climate coastal vegetation of South Africa that includes the Strandveld vegetation type. A. cyclops had 30–50% greater foliar N concentrations (P < 0.001) in comparison with the native species and lower foliar δ15N values that may indicate N2 fixation. Additionally, A. cyclops maintained higher photosynthetic rates over the dry summer season (ca. 15 μmol m−2 s−1) than the native species. These higher photosynthetic rates may result from sustained access to water due to deeper rooting abilities as indicated by the more negative δD values (P < 0.001) of A. cyclops (−43‰) in comparison with the some native species (−29 to −37‰). Acacia cyclops did not, however, exhibit greater water use efficiencies or photosynthetic nitrogen use efficiencies (P > 0.05) compared to native species. Invasiveness of A. cyclops into this resource‐limited Mediterranean‐climate ecosystem appears to be supported by greater resource acquisition, possibly partially through N2 fixation and greater rooting depth, rather than greater resource use efficiency or conservation.

Nitrogen Addition Increases the Sensitivity of Photosynthesis to Drought and Re-watering Differentially in C3 Versus C4 Grass Species.

Global change factors, such as variation in precipitation regimes and nitrogen (N) deposition, are likely to occur simultaneously and may have profound impacts on the relative abundance of grasses differing in functional traits, such as C3 and C4 species. We conducted an extreme drought and re-watering experiment to understand differences in the resistance and recovery abilities of C3 and C4 grasses under different N deposition scenarios. A C3 perennial grass (Leymus chinensis) and two C4 grasses (annual species Chloris virgata and perennial species Hemarthria altissima) that co-occur in Northeast China were selected as experimental plants. For both C3 and C4 grasses, N addition caused a strong increase in biomass and resulted in more severe drought stress, leading to a change in the dominant photosynthetic limitation during the drought periods. Although N addition increased antioxidant enzyme activities and protective solute concentrations, the carbon fixing capacity did not fully recover to pre-drought levels by the end of the re-watering period. N addition resulted in lower resilience under the drought conditions and lower resistance at the end of the re-watering. However, N addition led to faster recovery of photosynthesis, especially in the C3 grass, which indicate that the effect of N addition on photosynthesis during drought was asymmetric, especially in the plants with different photosynthetic nitrogen use efficiency (PNUE). These findings demonstrated that nitrogen deposition may significant alter the susceptibility of C3 and C4 grass species to drought stress and re-watering, highlighting the asymmetry between resistance and resilience and to improve our understanding about plant responses to climate change.

Growth and Physiology Vary Little Among North American, an Asian, and a North American x Asian Hybrid Ash in a Common Garden in Ohio, U.S.A

The emerald ash borer (EAB) (Agrilus planipennis Fairmaire) invasion of North America has increased interest in ash (Fraxinus, Oleaceae) phylogeny, ecology, and physiology. In a common garden in central Ohio, we compared the performance of three North American ash cultivars that are highly susceptible to EAB (F. pennsylvanica ‘Patmore,’ F. americana ‘Autumn Purple,’ and F. nigra ‘Fall Gold’), one North American species that is less susceptible to EAB (F. quadrangulata), and two taxa that are resistant to EAB (F. mandshurica and F. mandshurica × F. nigra ‘Northern Treasure’). During the 2015 growing season, we measured diameter growth, foliar N concentration, specific leaf area, and on four dates (two with adequate and two with low precipitation) we measured CO2 assimilation rate (A), stomatal conductance (gs), intercellular CO2 concentration (Ci), photosynthetic nitrogen use efficiency (PNUE), variable fluorescence (Fv’/Fm’: efficiency of energy harvested by open photosystem II reaction centers), and the fraction of photons absorbed by photosystem II that were used for photosynthesis (ɸPSII). F. pennsylvanica grew fastest and on most sampling dates was superior in physiological performance (A, gs, and ɸPSII). Generally, however, there was little interspecific variation in growth and physiology among the different ash taxa tested, as all performed well. This suggests that the EAB-resistant F. mandshurica and F. mandshurica × F. nigra hybrid, as well as the moderately resistant blue ash, are as physiologically well-suited to growing conditions in the Midwestern United States as green and white ash cultivars that had been widely planted prior to the EAB invasion.