Maximum Net Photosynthetic Rate Research Articles

Responses of photosynthetic characteristics of Phragmites australis to simulated warming in salt marshes of the Yellow Sea and Bohai Sea, China.

Coastal wetlands are highly efficient in blue carbon sequestration. The impacts of climate warming on photosynthetic rates and light response characteristics of wetland plants would change the magnitude of carbon sequestration in coastal wetlands. We constructed warming observation stations in Phragmites australis (Phragmites) wetlands located in the Yellow River Delta in Dongying with dry climate, and in Yancheng by the Yellow Sea with wet climate. By using a Li-6800 photosynthesis system, we investigated the responses of simulated warming on photosynthetic characteristics of Phragmites in both wetlands, and compared the difference between months (June and August) in Dongying wetland. The results showed the photosynthetic rates of Phragmites were higher in June than in August. Warming increased net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (gs) and intercellular carbon dioxide concentration (Ci) in the two months, but the variability of Pn to warming was lower in August. The Pn and water use efficiency (WUE) of Phragmites in the Yancheng wetland were higher than Dongying wetland, and the maximum net photosynthetic rate (Pn max), light saturation point (LSP), apparent quantum efficiency (AQY), and dark respiration rate (Rd) of the former responded more positively to warming. The values of AQY, LSP and Pn max of Phragmites in the Yancheng wetlands were increased by 16.7%, 53.6% and 30.3%, respectively, in the warming plots. Our results suggested that warming could improve the utilization efficiency of weak light, the adaptability to strong light and photosynthetic potential of Phragmites under rainy and humid conditions. This study is of importance for accurately quantifying carbon sequestration of coastal wetlands at the regional and seasonal scales in the context of climate warming.

Effect of nitrogen application on enhancing high-temperature stress tolerance of tomato plants during the flowering and fruiting stage.

This study was conducted to investigate the effects of nitrogen application on growth, photosynthetic performance, nitrogen metabolism activities, and fruit quality of tomato plants under high-temperature (HT) stress. Three levels of daily minimum/daily maximum temperature were adopted during the flowering and fruiting stage, namely control (CK; 18°C/28°C), sub-high temperature (SHT; 25°C/35°C), and high-temperature (HT; 30°C/40°C) stress. The levels of nitrogen (urea, 46% N) were set as 0 (N1), 125 (N2), 187.5 (N3), 250 (N4), and 312.5 (N5) kg hm2, respectively, and the duration lasted for 5 days (short-term). HT stress inhibited the growth, yield, and fruit quality of tomato plants. Interestingly, short-term SHT stress improved growth and yield via higher photosynthetic efficiency and nitrogen metabolism whereas fruit quality was reduced. Appropriate nitrogen application can enhance the high-temperature stress tolerance of tomato plants. The maximum net photosynthetic rate (P Nmax), stomatal conductance (g s), stomatal limit value (LS), water-use efficiency (WUE), nitrate reductase (NR), glutamine synthetase (GS), soluble protein, and free amino acids were the highest in N3, N3, and N2, respectively, for CK, SHT, and HT stress, whereas carbon dioxide concentration (C i), was the lowest. In addition, maximum SPAD value, plant morphology, yield, Vitamin C, soluble sugar, lycopene, and soluble solids occurred at N3-N4, N3-N4, and N2-N3, respectively, for CK, SHT, and HT stress. Based on the principal component analysis and comprehensive evaluation, we found that the optimum nitrogen application for tomato growth, yield, and fruit quality was 230.23kg hm2 (N3-N4), 230.02kg hm2 (N3-N4), and 115.32kg hm2 (N2), respectively, at CK, SHT, and HT stress. Results revealed that the high yield and good fruit quality of tomato plants at high temperatures can be maintained by higher photosynthesis, nitrogen efficiency, and nutrients with moderate nitrogen.

Trade-offs between leaf stoichiometric characteristics and photosynthetic traits of Larix gmelinii and its differences among provenances.

Variations and trade-offs between leaf stoichiometric characteristics and photosynthetic traits are indicative of ecological adaptation strategies of plants and their responses to environment changes. In a common garden of Maoershan, we measured leaf stoichiometric characteristics (carbon content (C), nitrogen content (N), phosphorus content (P), C/N, C/P, N/P) and photosynthetic traits (maximum net photosynthetic rate (Amax), maximum electron transport rate (Jmax), maximum carboxylation rate (Vmax)) of Larix gmelinii from 17 geographical provenances. We examined the provenance differences in stoichiometric characteristics and photosynthetic traits, and analyzed their trade-offs and influencing factors. The results showed leaf stoichiometric characteristics and photosynthetic traits significantly differed among provenances. The climatic factors of seed-source sites explained 54.8% and 67.2% of the variation in stoichiometric characteristics and photosynthetic traits, respectively. Aridity index (AI) of seed-source sites was positively correlated with C, N, P, Amax, Jmax, Vmax, but negatively with C/N, C/P, and N/P. Results of redundancy analysis showed that stoichiometric characteristics accounted for 75.0% of the variation in photosynthetic traits. Amax, Jmax, Vmax were positively correlated with C, N, P, and negatively correlated with C/N, C/P, N/P. The provenance differences in stoichiometric characteristics, photosynthetic traits, and their synergistic relationship suggested the long-term adaptation of trees to the climate of seed-source sites. These findings were of great significance for understanding ecological adaptation strategies of trees in response to climate change.

Mitigation of Elevated CO2 Concentration on Warming-Induced Changes in Wheat Is Limited under Extreme Temperature during the Grain Filling Period

Elevated CO2 concentration (eCO2) generally increases plant growth by improving photosynthesis, but it is unclear whether eCO2 can alleviate the negative effects of elevated temperatures, especially in high-temperature years. Manipulative experiments with elevated [CO2] and temperature were conducted in North China to understand the effect of elevated CO2 concentration and temperature on wheat. The photosynthesis, An–PAR and A–Ci curve parameters, growth period, biomass, yield component, and yield of wheat were investigated under different [CO2] (around 400 and 600 ppm) and temperatures (ambient temperature and ambient temperature +2 °C) for 3 years by using controlled chambers. Results showed that elevated temperature significantly shortened the growth period and decreased the yield and biomass of wheat. Elevated [CO2] significantly increased the maximum net photosynthetic rate (Anmax) but reduced the maximum carboxylation rate (Vcmax) and the maximum electron transport rate (Jmax). The extremely high temperature during the grain filling period in 2019 exerted a serious negative impact on wheat production. Elevated [CO2] stimulated photosynthesis, increased kernel number per spike, and extended the duration of the grain filling period, which consequently increased biomass and grain yield under elevated temperatures in normal years (2018 and 2020). Although the combination of CO2 and temperature reduced photosynthesis and biomass, it also alleviated the negative impact of elevated temperatures on grain yield to some extent under extremely high temperature during the grain filling period in 2019. The mitigative effect of eCO2 under extreme high temperature is limited, and planting early-maturing cultivars or increasing the genotypes of kernel number per spike help to escape the extreme high temperature of the critical growth period.

Photosynthesis prediction and light spectra optimization of greenhouse tomato based on response of red–blue ratio

Light is a key environmental variable regulating the growth and development of vegetables in controlled environment agriculture, and the red–blue ratio (R:B) plays an important role in photosynthesis, where the red and blue regions are considered as the main energy sources for photosynthetic CO2 assimilation. The photosynthesis response to the R:B of greenhouse tomatoes was investigated through the photosynthesis data corresponding to the R:B of 0.5, 1, 3, 5, 7, 9, pure blue, and pure red at various CO2 concentrations. The light response curves of the R:B were studied using the exponential model to identify the photosynthetic parameters of different R:B. The photosynthesis prediction model with light spectra based on incremental constructive extreme learning machine optimized by the sparrow search algorithm was established and used with evolutionary computation to obtain the R:B response curves and optimal R:B. Experimental results show that the determination coefficient of the prediction model in the testing set is 0.986, and the root mean square error is 0.833. At 25 °C, the R:B with the maximum net photosynthetic rate at 400, 700, and 1000 μmol CO2·mol−1 are 5.6, 5.8, and 6.6, respectively. The optimization of light spectra could improve the photosynthetic activity in plants, and the optimal light spectra could reduce the greenhouse energy consumption and light supplement in the environment.

The photosynthetic eco-physiological adaptability of the endangered plant Tetracentron sinense to different habitats and altitudes

Tetracentron sinense Oliv, the only tall deciduous tree in the family Tetracentraceae, is listed as a national second-grade key protected plant in China. To reveal the effect of associated species, irradiance, and altitudes on photosynthetic capacity of T. sinense, photosynthetic physiological characteristics of T. sinense and its associated species Acer pictum and Pterocarya stenoptera were measured by a Li-6400 portable photosynthetic meter. The light saturation point (LSP), the maximum net photosynthetic rate of the PN-PAR (PNmax), carboxylation efficiency (CE), the maximum net photosynthetic rate of the PN-CO2 (P*Nmax), carbon dioxide compensation point (CCP) and light respiration rate (Rp) of T. sinense in forest gap (FG) were higher than those in forest edge (FE) and understory (US). In FE, the net photosynthetic rate (PN), light compensation point (LCP), LSP, P*Nmax of T. sinense were lower than those of Pterocarya stenoptera, while the LSP, PNmax, and saturation point of carbon dioxide (Ciast) of T. sinense in US were lower than those of Acer pictum and Pterocarya stenoptera. The specific leaf area (SLA) of T. sinense decreased with reduction in the irradiance. With increasing altitude, the PNmax, LSP, and SLA of young individuals of T. sinense (YT) increased; the LCP of YT or the LSP of mature individuals of T. sinense (MT) increased first and then decreased. The results showed that 1) the photosynthetic capacity and adaptability of T. sinense were better in FG than that in FE and US; 2) the photosynthetic capacity of T. sinense in FE and US was weaker than that of its associated species, and its ecological range of light adaptation was also narrower than that of its associated species, placing T. sinense at a competitive disadvantage, which may be one of the important reasons for its poor regeneration; and 3) the environmental conditions at higher altitude can contribute to the growth and survival of T. sinense. Therefore, active artificial intervention should be undertaken to expand area of forest gap for T. sinense and transplant its seedlings to higher altitude to promote growth and population regeneration of T. sinense.

Cultivation model and deficit irrigation strategy for reducing leakage of bundle sheath cells to CO2, improve 13C carbon isotope, photosynthesis and soybean yield in semi-arid areas

A better understanding of the photosynthesis and soil water storage regulation of soybean production will be helpful to develop a water conservation strategy under a rain-fed farming system. Reducing the leakage of CO2 bundle sheath cells and improving the photosynthesis capacity and gas exchange characteristics of soybean leaves will contribute to increase yield under the dryland agricultural system and provide a scientific basis. Therefore, during 2019 and 2020, soybean exposed to different cultivation modes to analyze the response curves of photosynthesis and CO2 under different deficit irrigation strategies. In this study, we used two cultivation models: RB: ridge covered with biodegradable film and furrow area not covered; CF: conventional flat land planting under four deficit irrigation modes (R: rainwater irrigation; IB: branch stage irrigation (220 mm); IP: Irrigation during podding (220 mm); IBP: branch stage irrigation (110 mm), podding stage irrigation (110 mm). Compared with CF-IBP treatment, RB-IBP had significant effects on rainwater collection, SWS, and soybean yield. Photo-response curve analysis showed that RB-IBP treatment a significant increase in Pn, Gs, Ci, Tr, leaf WUE, and chlorophyll ab content. Under different irrigation strategies, maximum net photosynthetic rate (Pnmax), light saturation point (LSP), and apparent quantum efficiency under RB-IBP treatment (α), Pn under respiration rate and CO2 response curve were significantly higher than that under CF cultivation mode. Compared with RB culture mode under different irrigation strategies, CF cultivation mode significantly increases Δ13C and CO2 sheath cell leakage (Փ); it also led to a significant decline in the ratio of Ci/Ca concentration. This study shows that RB-IBP treatment is the best water-saving strategy because it means reducing the leakage of CO2 from the bundle sheath, thus significantly increasing soil water storage, photosynthetic capacity, and soybean yield.

Shading affects the starch structure and digestibility of wheat by regulating the photosynthetic light response of flag leaves

Heavy haze-induced decreases in solar radiation represent an important factor that affects the structural properties of starch macromolecules. However, the relationship between the photosynthetic light response of flag leaves and the structural properties of starch remains unclear. In this study, we investigated the impact of light deprivation (60 %) during the vegetative-growth or grain-filling stage on the leaf light response, starch structure, and biscuit-baking quality of four wheat cultivars with contrasting shade tolerance. Shading decreased the apparent quantum yield and maximum net photosynthetic rate of flag leaves, resulting in a lower grain-filling rate and starch content and higher protein content. Shading decreased the starch, amylose, and small starch granule amount and swelling power but increased the larger starch granule amount. Under shade stress, the lower amylose content decreased the resistant starch content while increasing the starch digestibility and estimated glycemic index. Shading during the vegetative-growth stage increased starch crystallinity, 1045/1022 cm−1 ratio, starch viscosity, and the biscuit spread ratio, while shading during the grain-filling stage decreased these values. Overall, this study indicated that low light affects the starch structure and biscuit spread ratio by regulating the photosynthetic light response of flag leaves.

Phytostimulator Application after Cold Stress for Better Maize (Zea mays L.) Plant Recovery

Phytostimulators are attracting considerable attention for replacing mineral fertilizers, which are of environmental concern, being especially forbidden in organic farming. The benefit of applying such products based on microorganisms (e.g., algae extract) or minerals of nano-meter-sized particle (e.g., nanofertilizers) is that plants can uptake them faster than soil fertilizers, targeting plant growth by regulating their phytohormones, as well as improving plant tolerance to unfavorable environmental conditions (e.g., cold stress). The aim of this study was to test and evaluate the effects of three commercial phytostimulators, called biostimulants (a seaweed-based extract—Kelpak®, mineral nanoparticles—Nano Active®, zinc nanoparticles—Dynamic Cresco®) on yield, chlorophyll content, level of CO2 assimilation and the effectiveness of PSII under cold stress. The values of all chlorophyll fluorescence and photosynthetic parameters significantly decreased under cold, which indicated a strong inhibition of light-phase photosynthesis in maize leaves. Predicted by the regression analysis minimum, 20 days was enough for maize plants to recover from the inhibition caused by stress damages in their photosynthetic apparatus. At the final measurement in maize growth stage BBCH 65, all the tested phytostimulators showed significant effects in increased values of effective quantum yield of photosystem II, maximum photosynthetic efficiency of PSII and electron transport rate. At this stage, Dynamic Cresco® and Nano Active® treatment significantly increased the value of maximum net photosynthetic rate (15.37% and 18.85%, respectively) and leaf chlorophyll content (7.8% and 8.7%, respectively). The application of Dynamic Cresco® significantly promoted total dry weight by 43.4% in comparison to control under stress growth conditions with cold. These phytostimulators can be used to enhance yield and physiological status of plants after abiotic stress (such as cold) to improve crop productivity, especially in organic farming.

Responses of the Growth Characteristics of Spinach to Different Moisture Contents in Soil under Irrigation with Magnetoelectric Water

Spinach (Spinacia oleracea L.) is a worldwide vegetable crop with rich nutritional value, and drought is the main factor restricting its growth. Magnetized water and de-electronated water have shown potential for improving yield and quality in some crops. To assess the influence of magnetized-de-electronated water (denoted magnetoelectric water) on the growth characteristics of spinach, five soil moisture gradients were developed, including 45–55%, 55–65%, 65–75%, 75–85%, and 85–95% of field capacity (FC). The results demonstrated that the influence of irrigation by magnetoelectric water on the growth of spinach was obvious. All the spinach indicators with each soil moisture gradient under irrigation by magnetoelectric water were higher than those of irrigation by conventional water, including the fresh weight of shoots, chlorophyll content, and the total nitrogen content in the leaves. In particular, the improvement in fresh weight of shoots and the total nitrogen contents in the leaves had the highest values, as demonstrated by increases of 52.26% and 25.87%, respectively, under 65–75% of the gradient of FC. Additionally, the fitting results of the photo response curve by different light response models varied. The modified rectangular hyperbolic model was the most accurate for all the treatment groups and thus was the optimized model for the photosynthetic characteristics of spinach under irrigation by magnetoelectric water analysis. The parameters of the photo response curve showed that the dark respiration rate, apparent quantum efficiency, light saturation point, and maximum net photosynthetic rate all increased following irrigation by magnetoelectric water with different soil moisture gradients compared with conventional water irrigation. These research results can provide new technical support for improving the water use efficiency of irrigation water and increasing vegetable production.

Do Tree Size and Tree Shade Tolerance Affect the Photosynthetic Capacity of Broad-Leaved Tree Species?

(1) Background: leaf structure traits are closely related to leaf photosynthesis, reflecting the ability of trees to obtain external resources in the process of growth. (2) Methods: We studied the morphological, chemical, anatomical, stomatal traits and maximum net photosynthetic rate of six broad-leaf species in northern temperate mixed broad-leaved Korean pine (Pinus koraiensis) forest. (3) Aim: To investigate whether there are differences in leaf structural traits of trees with different shade tolerances and different sizes and the effects of these differences on leaf photosynthetic capacity. (4) Results: the effects of leaf structure traits on leaf photosynthesis were different among trees with different shade tolerances or different sizes. Under the condition of light saturation, the net photosynthetic rate, nitrogen use efficiency, phosphorus use efficiency and stomatal conductance of shade-intolerant trees or small trees were higher than those of shade-tolerant trees or large trees. (5) Conclusions: the shade tolerance of tree species or the size of trees affect the traits of leaf structure and indirectly affect the photosynthetic ability of plants. When constructing the leaf trait-photosynthesis model, the shade tolerance and tree size of tree species should be taken into account.

Study on Heat Resistance of Peony Using Photosynthetic Indexes and Rapid Fluorescence Kinetics

To investigate the effects of high-temperature stress on the chlorophyll fluorescence induction kinetics of peony and to determine indicators for the rapid screening of varieties responding to high temperatures, three four-year-old peony variety, ‘Fengdanbai’, ‘Huhong’, and ‘Yinhongqiaodui’, were selected as materials. The photosynthetic curves (Pn-PAR) and fast chlorophyll fluorescence curves (OJIP curves) of peony leaves were measured at different times under high-temperature stress conditions (40 °C), the changes in the photosynthetic characteristics of different peony varieties under high-temperature stress were analyzed, and the heat tolerance of peony was evaluated. The results showed that ‘Huhong’ grew well within 16 days, while all of the other varieties showed obvious wilting at 6–9 days. High temperatures damaged the structure and function of the photosystem of peony leaves, indicating that the maximum net photosynthetic rate (Pnmax), apparent quantum efficiency (AQE), maximum photochemical efficiency (Fv/Fm), and photosynthetic performance index (PIABS) all tended to decrease under high-temperature stress, while the rate of closing the PS II reaction center (Mo) and the absorption per reaction center (ABS/RC), the capture (TRo/RC), and the dissipation (Dio/RC) of light energy per reaction center showed an overall increasing trend. The ability to cope with high-temperature stress differed among varieties, and the heat tolerance was determined to be in the descending order of ‘Fengdanbai’ < ‘Yinhongqiaodui’ < ‘Huhong’. The correlation analysis among the parameters and the analysis of the morphological change patterns in peony leaves concluded that PIABS, Dio/RC, and Mo could be used as indicators of peony tolerance to high-temperature stress. The results of the study can provide a basis for the screening of heat-tolerant peony species and peony heat defense in the Jiangnan area.

亚热带森林演替阶段下不同光环境对芒萁光合生理的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 亚热带森林演替阶段下不同光环境对芒萁光合生理的影响 DOI: 10.5846/stxb202112273661 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（31971623）；浙江省"尖兵""领雁"研发攻关计划项目（2022C02019） Effects of different light environments on photosynthetic physiology of Dicranopteris dichotoma under successional stages in subtropical forests Author: Affiliation: Fund Project: The National Natural Science Foundation of China (31971623)； 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:光环境的变化是群落演替进程中植物进入和退出群落的重要因素。为研究亚热带森林次生演替不同阶段的光照对芒萁光合生理的影响，对灌草丛、马尾松林和常绿阔叶林这3种群落内盆栽芒萁的光响应过程和叶绿素荧光诱导动力学参数进行了研究。结果表明：芒萁在光强为400 μmol m-2 s-1左右且日变化幅度较小的马尾松林下净光合速率（Pn）最高，在光强50 μmol m-2 s-1左右的常绿阔叶林下次之，在400-1800 μmol m-2 s-1左右波动的灌草丛内最低。这是因为灌草丛内芒萁J点相对可变荧光（Vj）、K点标准化后的相对可变荧光（Wk）显著升高，以吸收光能为基础的光系统Ⅱ性能指数（PSⅡ）（PIABS）显著降低，而热耗散参数（φDo）基本不变，即强光破坏了芒萁光合机构PSⅡ的供体侧和受体侧，使其产生了光抑制。常绿阔叶林内芒萁叶绿素荧光诱导动力学参数与马尾松林下差异不明显，且最大净光合速率（Pmax）下降是光强变弱导致的，但是暗呼吸速率（Rd）、光补偿点（LCP）和光饱和点（LSP）均随之降低，可见芒萁光合机构对该光强有一定的适应性。由此可知，芒萁喜光但不耐强光，对弱光具有一定耐受性。 Abstract:The light changes of forest succession play important roles in the presence or absence of plant species in communities. To reveal the effects of light on photosynthetic physiology of Dicranopteris dichotoma at different stages of secondary succession in subtropical forests, light response process and chlorophyll fluorescence induction kinetic parameters of D. dichotoma growing in three different communities (scrub, Pinus massoniana forest, and evergreen broadleaf forest) were investigated in this experiment. The results showed that the net photosynthetic rate (Pn) was the highest in the P. massoniana forest with a light intensity of about 400 μmol m-2 s-1 and a small daily variation, followed by the evergreen broadleaf forest with a light intensity of about 50 μmol m-2 s-1, and the lowest in the scrub with a fluctuation of about 400-1800 μmol m-2 s-1. The lowest Pn in the scrub was because high light disrupted donor and acceptor sides of photosystem II (PSII) of D. dichotoma, and resulted in photoinhibition of D. dichotoma, which were proved by significantly increased relative variable fluorescence (Vj) at point J, normalized relative variable fluorescence (Wk) at point K, and significantly decreased PSII performance index (PIABS), and unchanged heat dissipation parameter (φDo). No significant differences in chlorophyll fluorescence induction kinetics between the D. dichotoma growing in evergreen broad-leaved forest and P. massoniana forest indicated that its PSII was not damaged, and the decrease of the maximum net photosynthetic rate (Pmax) was caused by the low light. At the same time, the reduced dark respiration rate (Rd), light compensation point (LCP), and light saturation point (LSP) showed that D. dichotoma photosynthetic system could adapt to the low light in the evergreen broad-leaved forest. This study showed that D. dichotoma was a light-loving but not light-tolerant species, with the modest low-light tolerance. 参考文献 相似文献 引证文献

Leaf Traits and Resource Use Efficiencies of 19 Woody Plant Species in a Plantation in Fangshan, Beijing, China

Plantations are typically monocultures, which limits their sustainability. Therefore, understanding acclimatization strategies and resource use efficiencies in plant species and life forms aids the improvement of vegetation diversity and ecological functions. Here, 19 species from forest plantations in Fangshan, Beijing, China were studied. We determined their net photosynthetic (Pn), and transpiration rates (E), light response curve, stomatal conductance (gs), and leaf nitrogen (N) content. We analyzed the leaf N content (Nmass), specific leaf area (SLA), maximum net photosynthetic rate (Pnmax), water use (WUE), nitrogen use (NUE), and carbon use (CUE) efficiencies and connected them with both species and life forms. Pnmax, SLA, Nmass, WUE, NUE, and CUE significantly differed among species. Evergreen conifers had the lowest SLA and Nmass but the highest WUE and CUE. Evergreen coniferous trees had lower SLA, Nmass, Pnmax, and NUE but higher WUE than deciduous trees and shrubs. The SLA, Nmass, and Pnmax of nitrogen-fixing plants were the highest. A correlation analysis revealed that WUE was positively correlated with CUE and negatively correlated with NUE. Moreover, WUE was negatively correlated with Nmass and SLA. These insights into the adaptability differences of woody plant species and life forms provide a scientific basis for the selection of appropriate species for sustainable forest plantations.

Research on Control Strategy of Light and CO2 in Blueberry Greenhouse Based on Coordinated Optimization Model

As essential environmental parameters in the greenhouse, appropriate light and CO2 will improve agricultural productivity and quality. Although many related studies have been carried out on the intelligent regulation of these environmental factors, the regulation of light and CO2 is usually controlled separately, and energy consumption is rarely considered. This paper proposed a coordinated control strategy for greenhouse light and CO2 based on the multi-objective optimization model. Firstly, the experiments on the net photosynthetic rate of blueberry under different temperatures, photon flux density, and CO2 concentration nesting were carried out to establish a blueberry net photosynthetic rate prediction model based on Support Vector Regression (SVR). Secondly, a model for calculating the energy cost of both light and CO2 was constructed. Thirdly, taking the maximum net photosynthetic rate and the minimum energy cost as the objective functions, the Non-dominated Sorting Genetic Algorithm (NSGA-II) was leveraged to obtain the Pareto optimal solutions of the target regulation values of light and CO2 concentration in different temperature ranges. Then, the optimal values were selected based on two different strategies. Finally, the multi-objective optimal control strategy proposed in this paper was compared with both the classical threshold control strategy and the Gaussian curvature maximization control strategy. The results indicated that the strategy which prioritized energy saving could reduce the energy cost by about 22.33% and 19.08%, respectively, under the premise that the net photosynthetic rate was consistent. Meanwhile, the strategy that prioritized production efficiency could increase the net photosynthetic rate by about 8.40% and 4.42%, respectively, with the same energy cost. In conclusion, the proposed multi-objective optimization control can improve the greenhouse climate control performance and reduce cost compared with other mentioned strategies.

Exogenous Melatonin Improves Waterlogging Tolerance in Wheat through Promoting Antioxidant Enzymatic Activity and Carbon Assimilation

In a pot experiment, we explored the regulatory pathways through which melatonin (MT) protects wheat growth and grain yield loss from waterlogging injury. Two wheat cultivars, Yangmai 18 and Yannong 19, were exposed to seven days of soil waterlogging at flowering. Melatonin (100 μmol·L−1) was sprayed before and after waterlogging to explore its regulation on root growth, photosynthetic characteristics, dry matter accumulation, and grain yield. Soil waterlogging intensified malondialdehyde (MDA) and O2− production rates in wheat tissues, impairing leaf photosynthesis, biomass accumulation, and final grain yield formation. In this study, the roots waterlogged at 7 days after anthesis (DAA) accumulated 20.9%, 76.2%, 17.6%, 28.5%, and 5.6% higher MDA content, O2− production rate, pyruvate decarboxylase (PDC), lactate dehydrogenase (LDH), and alcohol dehydrogenase (ADH) activities, respectively, in Yangmai 18, and 25.7%, 74.8%, 35.8%, 70.8%, and 30.7% higher in Yannong 19, respectively, compared with their respective non-waterlogged controls. Further, Yangmai 18 achieved a maximum net photosynthetic rate (Pn) reduction of 22.1% at 7 DAA, while the maximum Pn reduction of Yannong 19 was 27.4% at 14 DAA, respectively, compared with their respective non-waterlogged plants. Thus, waterlogging decreased total dry matter accumulation, 1000-grain weight (TGW), and total grain yield by 14.0%, 13.8%, and 16.2%, respectively, in Yangmai 18, and 16.0%, 8.1%, and 25.1%, respectively, in Yannong 19. Our study also suggests that exogenously applied melatonin can protect wheat root tissues from waterlogging-induced oxidative injury by upregulating antioxidant enzymes and sustaining leaf photosynthesis. The plants treated with melatonin showed better water status and less oxidative damage, which was conducive to maintaining a higher photosynthetic capacity, thereby improving the waterlogging tolerance of wheat. For example, compared with waterlogged plants, melatonin treatments significantly reduced MDA content, O2− production rate, PDC, LDH, and ADH activities by 7.7%, 25.4%, 2.6%, 32.1%, and 3.2%, respectively, in Yangmai 18, and 6.7%, 17.9%, 4.1%, 22.0%, and 15.3%, respectively, in Yannong 19. MT treatments significantly increased total dry matter accumulation, TGW, and yield by 5.9%, 8.7%, and 14.9%, respectively, in Yangmai 18, and 3.2%, 7.3%, and 26.0%, respectively, in Yannong 19.

Physiological Adaptation Mechanisms to Drought and Rewatering in Water-Saving and Drought-Resistant Rice.

Water-saving and drought-resistant rice (WDR) has high a yield potential in drought. However, the photosynthetic adaptation mechanisms of WDR to drought and rehydration have yet to be conclusively determined. Hanyou 73 (HY73, WDR) and Huanghuazhan (HHZ, drought-sensitive cultivar) rice cultivars were subjected to drought stress and rewatering when the soil water potential was -180 KPa in the booting stage. The leaf physiological characteristics were dynamically determined at 0 KPa, -30 KPa, -70 KPa, -180 KPa, the first, the fifth, and the tenth day after rewatering. It was found that the maximum net photosynthetic rate (Amax) and light saturation point were decreased under drought conditions in both cultivars. The change in dark respiration rate (Rd) in HY73 was not significant, but was markedly different in HHZ. After rewatering, the photosynthetic parameters of HY73 completely returned to the initial state, while the indices in HHZ did not recover. The antioxidant enzyme activities and osmoregulatory substance levels increased with worsening drought conditions and decreased with rewatering duration. HY73 had higher peroxidase (POD) activity as well as proline levels, and lower catalase (CAT) activity, ascorbate peroxidase (APX) activity, malondialdehyde (MDA) level, and soluble protein (SP) content during all of the assessment periods compared with HHZ. In addition, Amax was markedly negatively correlated with superoxide dismutase (SOD), POD, CAT, and SP in HY73 (p < 0.001), while in HHZ, it was negatively correlated with SOD, CAT, APX, MDA, Pro, and SP, and positively correlated with Rd (p < 0.001). These results suggest that WDR has a more simplified adaptation mechanism to protect photosynthetic apparatus from damage in drought and rehydration compared with drought-sensitive cultivars. The high POD activity and great SP content would be considered as important physiological bases to maintain high photosynthetic production potential in WDR.

Isolation, identification, and evaluation of an ectomycorrhizal fungus from a hazel orchard in China

Mycorrhizal relationships improve the availability of water and nutrients to their plant partners, thereby improving plant growth and stress resistance. However, little is known about mycorrhizal relationships in the hybrid hazel Corylus heterophylla × C. avellana, which is the main source of hazelnuts in China. The aims of this study were to analyze the diversity of rhizosphere microbes from hazel orchards with and without mycorrhizae, to isolate and identify fungi associated with hazel mycorrhizae and to evaluate the effects of mycorrhizal fungi inoculation on potted hazel seedlings. The results of diversity analysis of rhizosphere microbes showed that Scleroderma accounted for 97.07 % of the sequences generated from the rhizosphere of the mycorrhizae-associated orchard, which was markedly higher than the 0.13 % of sequences generated from the orchard without mycorrhizae. A mycorrhizal strain was isolated and purified, and an obvious clamp-connection structure was observed in its hypha, which clearly indicated that this fungus was a member of basidiomycetes. Paraffin slices of artificially produced mycorrhizae revealed external hyphae, mantle, and Hartig net, which suggested that the isolated fungus was ectomycorrhizal. Furthermore, the ITS1–ITS4 sequences of the fungus showed 99.82 % similarity with Scleroderma bovista Fr. Finally, inoculation of hazel seedling with mycorrhizal fungi significantly increased its height, stem diameter, chlorophyll content, leaf area, aboveground fresh weight, underground fresh weight, and total plant weight by 2.02, 1.54, 2.14, 3.80, 2.70, 2.25, and 2.56 times, respectively. It also significantly (5 % significance level) promoted root length; project area; surface area; volume; mean diameter; and number of tips, forks, and crosses. Furthermore, it promoted photosynthesis-related parameters, such as CO2 saturation point, RuBP maximum regulation rate, carbon efficiency, light saturation point, maximum net photosynthetic rate, and approximate quantum efficiency. These findings demonstrated the S. bovista strain promoted growth in hazel trees and that it has potential prospects for application in raising hazel seedlings and their cultivation.

Leaf Photosynthetic and Functional Traits of Grassland Dominant Species in Response to Nutrient Addition on the Chinese Loess Plateau

Leaf photosynthetic and functional traits of dominant species are important for understanding grassland community dynamics under imbalanced nitrogen (N) and phosphorus (P) inputs. Here, the effects of N (N0, N50, and N100, corresponding to 0, 50, and 100 kg ha-1 yr-1, respectively) or/and P additions (P0, P40, and P80, corresponding to 0, 40, and 80 kg ha-1 yr-1) on photosynthetic characteristics and leaf economic traits of three dominant species (two grasses: Bothriochloa ischaemum and Stipa bungeana; a leguminous subshrub: Lespedeza davurica) were investigated in a semiarid grassland community on the Loess Plateau of China. Results showed that, after a three-year N addition, all three species had higher specific leaf area (SLA), leaf chlorophyll content (SPAD value), maximum net photosynthetic rate (PNmax), and leaf instantaneous water use efficiency (WUE), while also having a lower leaf dry matter content (LDMC). The two grasses, B. ischaemum and S. bungeana, showed greater increases in PNmax and SLA than the subshrub L. davurica. P addition alone had no noticeable effect on the PNmax of the two grasses while it significantly increased the PNmax of L. davurica. There was an evident synergetic effect of the addition of N and P combined on photosynthetic traits and most leaf economic traits in the three species. All species had relatively high PNmax and SLA under the addition of N50 combined with P40. Overall, this study suggests that N and P addition shifted leaf economic traits towards a greater light harvesting ability and, thus, elevated photosynthesis in the three dominant species of a semiarid grassland community, and this was achieved by species-specific responses in leaf functional traits. These results may provide insights into grassland restoration and the assessment of community development in the context of atmospheric N deposition and intensive agricultural fertilization.

Nitrogen Allocation Tradeoffs Within-Leaf between Photosynthesis and High-Temperature Adaptation among Different Varieties of Pecan (Carya illinoinensis [Wangenh.] K. Koch).

Interpreting leaf nitrogen (N) allocation is essential to understanding leaf N cycling and the economy of plant adaptation to environmental fluctuations, yet the way these mechanisms shift in various varieties under high temperatures remains unclear. Here, eight varieties of pecan (Carya illinoinensis [Wangenh.] K. Koch), Mahan, YLC10, YLC12, YLC13, YLC29, YLC35, YLJ042, and YLJ5, were compared to investigate the effects of high temperatures on leaf N, photosynthesis, N allocation, osmolytes, and lipid peroxidation and their interrelations. Results showed that YLC35 had a higher maximum net photosynthetic rate (Pmax) and photosynthetic N-use efficiency (PNUE), while YLC29 had higher N content per area (Na) and lower PNUE. YLC35, with lower malondialdehyde (MDA), had the highest proportions of N allocation in rubisco (Pr), bioenergetics (Pb), and photosynthetic apparatus (Pp), while YLC29, with the highest MDA, had the lowest Pr, Pb, and Pp, implying more leaf N allocated to the photosynthetic apparatus for boosting PNUE or to non-photosynthetic apparatus for alleviating damage. Structural equation modeling (SEM) demonstrated that N allocation was affected negatively by leaf N and positively by photosynthesis, and their combination indirectly affected lipid peroxidation through the reverse regulation of N allocation. Our results indicate that different varieties of pecan employ different resource-utilization strategies and growth-defense tradeoffs for homeostatic balance under high temperatures.