Maximum Net Photosynthetic Rate Research Articles

Transplanting larch trees into warmer areas increases the photosynthesis and its temperature sensitivity.

To investigate the effects of climate warming on photosynthesis, Dahurian larch (Larix gmelinii Rupr.) trees from four sites (spanning ~ 5.5° in latitude and~4 °C of warming) within the geographic range in China were transplanted into a common garden close to the warmer border in 2004. Throughout the growing season of 2018, the CO2- and temperature-response curves of the photosynthesis in the common garden and at the original sites were measured. It was discovered that warming treatment considerably increased the maximum net photosynthetic rate (Amax) by 23.4-35.3% depending on the sites, signifying that warming upregulated Amax with respect to the degree of warming. At 25 °C, warming enhanced the maximum Rubisco carboxylation rate (Vcmax), maximum electron transport rate (Jmax), and mass-based leaf nitrogen concentration (Nmass). The climate warming effect (CWE) on Amax was positively associated with the CWEs on Vcmax, Jmax and Nmass, which indicated that warming promoted Amax primarily via increasing carboxylation and photosynthetic electron transport rates and leaf nitrogen supply. The CWE in optimal photosynthetic temperature (Topt) was significant for the trees from the northern sites rather than the southern sites; however, the effect vanished for the trees transplanted to the common garden; this implied that Topt exhibited limited local thermal acclimation. Nevertheless, warming narrowed the temperature-response curve, the effect of which was positively associated with the warming magnitude. These findings implied that trees transplanted into warmer areas changed the photosynthetic optimum temperature and sensitivity. In summary, our results deepen the understanding of the underlying mechanisms of intraspecific responses of photosynthesis to temperature changes, including which of the modeling would improve the prediction of tree growth and forest carbon cycling under climate warming.

Intraspecific variation in growth‐related traits—from leaf to whole‐tree—in three provenances of Cryptomeria japonica canopy trees grown in a common garden

AbstractTo elucidate the physiological and morphological factors underlying intraspecific variation in growth rate, we examined the variation in leaf and whole‐tree traits for three geographical variations of ca. 45‐year‐old Japanese cedar (Cryptomeria japonica D. Don) with contrasting heights and radial growth in a common garden. Traits that reflect leaf‐level photosynthesis, water relations, and whole‐tree level crown structure in relation to light use and hydraulic architecture were measured. Overall, intraspecific variation in growth characteristics in field‐grown adult trees was regulated by whole‐tree properties rather than leaf properties. Most leaf traits were similar among provenances. Nevertheless, the leaf traits exhibited highest maximum net photosynthetic rate, dark respiration rate, and light compensation point in provenances whose native habitats are most similar to the common garden in the present study. Together with previous reports that this provenance has higher root nutrient acquisition capacity than the other two provenances, it can be said that organ‐level resource use strategies are coupled in a tandem manner. At the whole‐tree level, hydraulic architecture—as explained by axial variation in the hydraulically weighted tracheid diameter—can be linked to leaf distribution with respect to light use strategies as well as water transport capacity, leading to differences in growth characteristics among provenances. The study of intraspecific variation in growth characteristics in trees with a wide range of native habitats is expected to be a useful indicator for predicting changes in growth potential and forest dynamics in response to climate change in each habitat.

Exogenous uniconazole enhances tolerance to chilling stress in mung beans (Vigna radiata L.) through cross talk among photosynthesis, antioxidant system, sucrose metabolism, and hormones

To monitor the role of exogenous uniconazole in mitigating chilling stress, this study investigated the effect of foliar spraying of 50 mg L−1 uniconazole on the chilling (15 °C) tolerance of mung beans at the flowering stage. The results showed that uniconazole significantly enhanced the reactive oxygen species (ROS) scavenging ability of mung beans by increasing the superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX), glutathione reductase (GR) activities, the contents of ascorbic acid (AsA) and glutathione (GSH), and the transcription levels of SOD and POD under chilling stress. The uniconazole applications also drastically increased the net photosynthetic rate (Pn), maximum net photosynthetic rate (Pnmax), maximum quantum yield of PSII (Fv/Fm), and the expression levels of the corresponding photosynthetic genes PsbO, PsbP, PsbQ, PsbY, and Psb28. This, in turn, resulted in a higher sucrose content. Meanwhile, uniconazole increased the indole-3-acetic acid (IAA) content but reduced the gibberellin A3 (GA3) content under chilling stress. During the recovery period, the photosynthetic parameters and ROS of plants receiving uniconazole recovered faster, and the antioxidant activity and non-antioxidant contents were higher than in chilling-treated plants. Additionally, chilling stress markedly reduced the pod number per plant, grain number per plant, and 100-seed weight, whereas uniconazole significantly increased the grain weight per plant by 53.47% compared to the chilling treatment. These results strongly suggest that uniconazole can effectively protect mung beans from chilling stress damage by protecting the photosynthetic machinery and enhancing the antioxidant capacity to quench excessive ROS caused by chilling stress. These effects are closely relevant to chilling tolerance enhancement and yield improvement in mung beans.

Trait value and phenotypic integration contribute to the response of exotic Rhus typhina to heterogeneous nitrogen deposition: A comparison with native Rhus chinensis

The temporal heterogeneity of nitrogen availability in soils is increasing due to agricultural deposition. We here compared the effects of gradually increasing nitrogen deposition rate and its increasing temporal heterogeneity patterns on the functional traits of seedlings of exotic species Rhus typhina and the native species Rhus chinensis. Nitrogen deposition rates of 0, 8, 20 g N m−2 year−1 and constant, single-peak, and double-peak nitrogen were added to simulate deposition rate and temporal heterogeneity. After 60 days of treatment, R. typhina seedlings had several advantageous growth trait values, such as higher total biomass production, but lower phenotypic plasticity than R. chinensis seedlings. R. typhina seedlings also had higher phenotypic integration, measured as the correlation among functional traits. The increased nitrogen deposition rate affected several traits of the two species differently. Thus, while R. chinensis seedlings allocated more biomass to leaves and less to roots with increasing N deposition, R. typhina seedlings had stable biomass allocation among all N treatments. Chlorophyll content, leaf phosphorus concentration, and water use efficiency increased, but the maximum net photosynthetic rate decreased, with N availability in R. chinensis, but not in R. typhina. Temporal heterogeneity had no significant effect on the total biomass of R. typhina and R. chinensis seedlings. Overall, the performance of R. typhina is better than that of R. chinensis seedlings under different nitrogen deposition treatments, which is due to the significantly advantageous trait values and greater phenotypic integration of R. typhina seedlings, whereas R. chinensis seedlings have higher phenotypic plasticity.

Effects of Nitrogen and Phosphorus Addition on Agronomic Characters, Photosynthetic Performance and Anatomical Structure of Alfalfa in Northern Xinjiang, China

The productivity of alfalfa is associated with a large amount of nitrogen (N) and phosphorus (P); the addition of exogenous N and P fertilizers can fully exploit the growth potential of alfalfa. However, there is uncertainty about the relationship between changes in alfalfa productivity and photosynthetic physiology and anatomy. We conducted field fertilization experiments on alfalfa in the second and third years under drip irrigation, as well as measurement of the photosynthetic physiology, anatomical structure and agronomic traits of alfalfa at different levels of N (0, 120 kg·ha−1) and different levels of P2O5 (0, 50, 100 and 150 kg·ha−1). The results showed that the dry matter yield (DMY), crude protein (CP), net photosynthetic rate (Pn) and specific leaf weight (SLW) were increased by 2.10~11.82%, 4.95~11.93%, 4.71~7.59% and 2.02~7.12% in the N application treatment compared with the non-N application treatment, while the DMY, CP, Pn and SLW were increased by 3.19~17.46%, 1.99~8.42%, 6.15~24.95% and 2.16~11.90% in the P application treatment compared with the non-P application treatment. N and P increase the thickness of the spongy tissue (ST) of alfalfa, which will facilitate the entry and exit of gas and water, and will further affect the photosynthetic indexes, such as stomatal conductance (Gs) and transpiration rate (Tr), of alfalfa leaves. Increased palisade tissue (PT) thickness will also enhance the adaptability of plant leaves to strong sunlight, thereby increasing the maximum net photosynthetic rate (Pmax) and light saturation point (LSP). Fertilization treatment showed the highest utilization efficiency for low light and better adaptation to strong light, but the Rd decreased. The comprehensive scores of principal component analysis for anatomical structure, photosynthetic performance and agronomic traits were N1P2 > N0P2 > N1P3 > N1P1 > N0P3 > N0P1 > N1P0 > N0P0. Therefore, the application of N and P fertilizers contributed to the adaptive changes in alfalfa leaf anatomy and the improvement of photosynthetic capacity, which were beneficial to the improvement of alfalfa dry matter yield, growth traits and nutritional quality, with the most obvious improvement effect obtained with the application of 120 kg·ha−1 of N and 100 kg·ha−1 of P2O5.

Effects of Groundwater Mineralization and Groundwater Depth on Eco-Physiological Characteristics of Robinia pseudoacacia L. in the Yellow River Delta, China

Groundwater plays a significant role in influencing the growth and distribution of Robinia pseudoacacia L. plantations, with the largest planting area in the Yellow River Delta, by affecting the soil water–salt environment. This study aimed to clarify the mechanism of groundwater’s influence on the growth of R. pseudoacacia under different levels of groundwater mineralization (GWM) and groundwater depth (GWD). We simulated GWM of 0, 2 and 4 g L−1, and GWD of 0.8, 1.3 and 1.8 m. As GWM increased, soil relative water content (SRWC) and soil salt (dissolved salt) content (SSC) increased; sapling biomass (SB), stem mass (SM), leaf mass (LM), photosynthesis characteristics (maximum net photosynthetic rate (Pn), stomatal conductance (gs), intercellular CO2 concentration (Ci), transpiration rate (E) and water use efficiency (WUE)) decreased; root mass (RM), root mass ratio (RMR) and root–shoot ratio (RSR) first increased then decreased; stem mass ratio (SMR) first decreased then increased; and leaf mass ratio (LMR) increased. As GWD increased, SRWC decreased, but SSC first increased then decreased; SB, RM, RMR, RSR, and photosynthesis characteristics increased; SM and LM first increased then decreased; and SMR and LMR decreased. SRWC and SSC were negatively correlated with SB and photosynthesis characteristics. SRWC was negatively correlated with RMR and RSR, whereas it was positively correlated with LMR. SSC was negatively correlated with SMR, whereas it was positively correlated with LMR. The first principal component, including SB, RM, and photosynthesis characteristics, was related to sapling growth. The second principal component, including RMR, SMR, and RSR, was mainly related to biomass allocation. In conclusion, GWM and GWD affected the soil water and salt content, which were key factors influencing the photosynthesis and growth of R. pseudoacacia. Adjustments in biomass allocation and photosynthesis were the main adaptive strategies of R. pseudoacacia to salt, drought, and flooding stress.

Effects of Water Availability on the Relationships Between Hydraulic and Economic Traits in the Quercus wutaishanica Forests.

Water availability is a key environmental factor affecting plant species distribution, and the relationships between hydraulic and economic traits are important for understanding the species’ distribution patterns. However, in the same community type but within different soil water availabilities, the relationships in congeneric species remain ambiguous. In northwest China, Quercus wutaishanica forests in the Qinling Mountains (QM, humid region) and Loess Plateau (LP, drought region) have different species composition owing to contrasting soil water availability, but with common species occurring in two regions. We analyzed eight hydraulic traits [stomatal density (SD), vein density (VD), wood specific gravity (WSGbranch), lower leaf area: sapwood area (Al: As), stomatal length (SL), turgor loss point (ΨTlp), maximum vessel diameter (Vdmax) and height (Height)] and five economic traits [leaf dry matter content (LDMC), leaf tissue density (TD), leaf dry mass per area (LMA), Leaf thickness (LT) and maximum net photosynthetic rate (Pmax)] of congeneric species (including common species and endemic species) in Q. wutaishanica forests of QM and LP. We explored whether the congeneric species have different economic and hydraulic traits across regions. And whether the relationship between hydraulic and economic traits was determined by soil water availability, and whether it was related to species distribution and congeneric endemic species composition of the same community. We found that LP species tended to have higher SD, VD, WSGbranch, Al: As, SL, ΨTlp and Vdmax than QM species. There was a significant trade-off between hydraulic efficiency and safety across congeneric species. Also, the relationships between hydraulic and economic traits were closer in LP than in QM. These results suggested that relationships between hydraulic and economic traits, hydraulic efficiency and safety played the role in constraining species distribution across regions. Interestingly, some relationships between traits changed (from significant correlation to non-correlation) in common species across two regions (from LP to QM), but not in endemic species. The change of these seven pairs of relationships might be a reason for common species’ wide occurrence in the two Q. wutaishanica forests with different soil water availability. In drought or humid conditions, congeneric species developed different types of adaptation mechanisms. The study helps to understand the environmental adaptive strategies of plant species, and the results improve our understanding of the role of both hydraulic and economic traits during community assembly.

Cold Stress Resistance of Tomato (Solanum lycopersicum) Seedlings Is Enhanced by Light Supplementation From Underneath the Canopy.

Adverse environmental conditions, such as low temperature (LT), greatly limit the growth and production of tomato. Recently, light-emitting diodes (LEDs) with specific spectra have been increasingly used in horticultural production facilities. The chosen spectrum can affect plant growth, development, and resistance, but the physiological regulatory mechanisms are largely unknown. In this study, we investigated the effects of LED light supplementation (W:B = 2:1, light intensity of 100 μmol⋅m–2⋅s–1, for 4 h/day from 9:00 to 13:00) from above and below the canopy on tomato resistance under sub-LT stress (15/8°C). The results showed that supplemental lighting from underneath the canopy (USL) promoted the growth of tomato seedlings, as the plant height, stem diameter, root activity, and plant biomass were significantly higher than those under LT. The activity of the photochemical reaction center was enhanced because of the increase in the maximal photochemical efficiency (Fv/Fm) and photochemical quenching (qP), which distributed more photosynthetic energy to the photochemical reactions and promoted photosynthetic performance [the maximum net photosynthetic rate (Pmax) was improved]. USL also advanced the degree of stomatal opening, thus facilitating carbon assimilation under LT. Additionally, the relative conductivity (RC) and malondialdehyde (MDA) content were decreased, while the soluble protein content and superoxide dismutase (SOD) activity were increased with the application of USL under LT, thereby causing a reduction in membrane lipid peroxidation and alleviation of stress damage. These results suggest that light supplementation from underneath the canopy improves the cold resistance of tomato seedlings mainly by alleviating the degree of photoinhibition on photosystems, improving the activity of the photochemical reaction center, and enhancing the activities of antioxidant enzymes, thereby promoting the growth and stress resistance of tomato plants.

Leaf anatomy, photosynthesis, and chloroplast ultrastructure of Heptacodium miconioides seedlings reveal adaptation to light environment

Light intensity is a critical factor for the plant survival and early growth. Heptacodium miconioides , a well-accepted ornamental plant, has been endangered due to fragmented habitats in the wild. To better understand the light adaptation mechanisms of H. miconioides , we investigated the morphology, photosynthesis, chloroplast ultrastructure, and chloroplast gene expression of the leaves under high light (HL), moderate light (ML), and low light (LL) conditions. With decreasing light intensity, the specific leaf area and chlorophyll contents of H. miconioides increased, whereas the leaf size first increased followed by a decrease. The maximum net photosynthetic rate under ML and HL treatments were significantly higher than that under LL treatment. However, leaves under ML treatment exhibited the lower dark respiration rate and light compensation point than those under HL treatment. The leaf thickness, palisade tissue, spongy tissue, and stomatal density were obviously reduced with decreasing light intensity. Chloroplast ultrastructure showed the better development in leaves under ML condition, and the size of chloroplast, the number of starch grains and plastoglobules increased significantly. In addition, the expression levels of genes involved in chlorophyll biosynthesis ( HEMA , CLH , CHLI , CHLH , CHLG ) were higher under ML than LL treatment, but lower under HL treatment. The up-regulation of the photosystem II ( PsbB , PsbD , PsbO ) genes expression play an important role in under ML and LL treatments. Taken together, we proposed that the optimal growth of H. miconioides seedlings varies between HL and ML but had poor growth under LL condition. The improvement in H. miconioides growth under moderate shade was mainly through its effects on leaf morphology, chloroplast development, and light capture efficiency of PSII phase. • Adaptation mechanisms to different light intensity were investigated in Heptacodium miconioides . • Seedlings grown under moderate and high light intensities exhibited higher photosynthetic capacity. • Moderate light intensity increased the size of chloroplast and the accumulation of starch grains and plastoglobules. • Moderate light intensity up-regulated chlorophyll biosynthesis and photosystem II (PSII) related gene expression.

Effects of groundwater depth on functional traits of young Haloxylon ammodendron.

Groundwater is an important water source for phreatophytic shrubs in arid desert areas. In order to understand the impacts of groundwater depth on functional traits of phreatophytic shrubs, two groups of groundwater levels (2 and 3.5 m) were set up using lysimeter with automatic water replenishing instrument. We measured hydraulic traits, gas exchange characteristics, and root morphological parameters of young Haloxylon ammodendron during the growing season. The results showed that predawn assimilating branch water potential, osmotic potential at full turgor, and root length ratio of young H. ammodendron in the groundwater depth of 3.5 m were lower by 48.2%, 41.5% and 56.7% than that under groundwater depth of 2 m, respectively, while maximum net photosynthetic rate of late growing season, root volume, specific root length and specific root area of fine root were 75.7%, 41.0%, 273.7% and 67.7% higher, respectively. Midday water potential and water content of assimilating branch tended to decrease first in the early growing season and then increase in the late growing season. Root distribution of young H. ammodendron along soil profile showed a significant positive correlation between the average root diameter and soil depth, while the proportion of fine root surface area showed a significant negative correlation with soil depth at both groundwater levels. There was synergy of aboveground assimilating branch hydraulic traits and photosynthetic capacity with belowground root morphological traits in young H. ammodendron. Under the condition of increasing groundwater depth, young H. ammodendron adopted the ecological strategies of reducing predawn assimilating branch water potential and osmotic potential at full turgor, and increasing root diameter and length to enhance water deficit tolerance and expanding the area of water uptake to sustain their survival.

Estimating Light Acclimation Parameters of Cucumber Leaves Using Time-Weighted Averages of Daily Photosynthetic Photon Flux Density.

Leaves acclimate to day-to-day fluctuating levels of photosynthetic photon flux density (PPFD) by adjusting their morphological and physiological parameters. Accurate estimation of these parameters under day-to-day fluctuating PPFD conditions benefits crop growth modeling and light environment management in greenhouses, although it remains challenging. We quantified the relationships between day-to-day PPFD changes over 6 days and light acclimation parameters for cucumber seedling leaves, including leaf mass per area (LMA), chlorophyll (Chl) a/b ratio, maximum net photosynthetic rate (Pnmax), maximum rate of ribulose-1,5-bisphosphate (RuBP) carboxylase/oxygenase (Vcmax), and maximum rate of electron transport (Jmax). The last two parameters reflect the capacity of the photosynthetic partial reactions. We built linear regression models of these parameters based on average or time-weighted averages of daily PPFDs. For time-weighted averages of daily PPFDs, the influence of daily PPFD was given a specific weight. We employed three types of functions to calculate this weight, including linear, quadratic, and sigmoid derivative types. We then determined the trend of weights that estimated each parameter most accurately. Moreover, we introduced saturating functions to calibrate the average or time-weighted averages of daily PPFDs, considering that light acclimation parameters are usually saturated under high PPFDs. We found that time-weighted average PPFDs, in which recent PPFD levels had larger weights than earlier levels, better estimated LMA than average PPFDs. This suggests that recent PPFDs contribute more to LMA than earlier PPFDs. Except for the Chl a/b ratio, the average PPFDs estimated Pnmax, Vcmax, and Jmax with acceptable accuracy. In contrast, time-weighted averages of daily PPFDs did not improve the estimation accuracy of these four parameters, possibly due to their low response rates and plasticity. Calibrating functions generally improved estimation of Chl a/b ratio, Vcmax, and Jmax because of their saturating tendencies under high PPFDs. Our findings provide a reasonable approach to quantifying the extent to which the leaves acclimate to day-to-day fluctuating PPFDs, especially the extent of LMA.

Analysis of leaf-architecture characteristics and ecological adaptability of tree species in the upper reaches of the Chishui River

The leaf-architecture characteristics of 15 ligneous plants of the karst region of the upper reaches of the Chishui River were assessed using spatial syntax. Furthermore, the relationship between leaf-architecture characteristics, plant functional traits, and soil water-holding capacity as well as the adaptation of plant architecture to this habitat were explored. The following results were obtained: (1) The integration, connectivity, and control of primary veins are significantly better than those of secondary veins, indicating strong interveinal ranking. The integration, connectivity, and control of evergreen tree species are superior to those of deciduous tree species, suggesting a more complex spatial morphological structure of evergreen leaves. In evergreen trees, the spatial morphological structure of tree leaves is more complex than that of shrubs, while the spatial morphological structure of tree leaves of deciduous trees is simpler than that of shrubs. (2) The dry matter content of the leaves of the investigated 15 ligneous plants ranged from 10.79 to 31.83 mg·g−1. The leaf relative water deficit, maximum net photosynthetic rate, transpiration rate, and the specific leaf area content ranged from 35.15 to 66.53%, 0.4–32 μmol·m−2·s−1, 0.07–0.71 g·cm−2·h−1, and 230.15–585.39 cm2·g−1, respectively. (3) The spatial syntax index is significantly correlated with transpiration rate, leaf relative water deficit, as well as soil maximum and available water-holding capacity. (4) Based on the spatial morphological structure of leaves, four basic modes of the leaf architecture can be classified: evergreen mode with complex morphological leaf-structure, evergreen mode with lower complex morphological leaf-structure, mixed evergreen and deciduous modes with lower complex leaf-morphological structure, and deciduous mode with simple morphological leaf-structure. (5) The spatial morphological structure of leaves in karst areas effectively exposes differences of architecture among different plants. Space syntax effectively represents leaf-architecture characteristics and is important for the study of plant architecture. Understanding plant architecture characteristics and their adaptation to the environment provides a scientific basis for the selection of tree species and planting patterns in the vegetation restoration area.

How Does Deforestation Affect the Growth of Cypripedium (Orchidaceae) Species? A Simulation Experiment in Northeast China

Due to wild habitat destruction, Cypripedium is among the most endangered groups in China. Determining how Cypripedium respond to environmental changes is curial to their conservation. However, less is known about the effect of deforestation on the growth of Cypripedium. In this study, we selected four Cypripedium species in Northeast China, and conducted conservation-based transplantation simulating deforestation to explore the impact of increased light intensity on the growth of Cypripedium. After three years, the maximum net photosynthetic rate was decreased by 15.9%, 11.5%, 13.6% and 5.3% for C. calceolus L., C. guttatum Sw., C. macranthos Sw. and C.×ventricosum Sw., respectively, resulting in poor viability, manifesting as shorter and thinner shoots, and smaller leaves. Unexpectedly, no significant traits shifts were found in the roots across four species, which may be related to the long root lifespan and conservation. Our research confirmed that increased light intensity caused by deforestation would lead to an increase in respirate cost and a decrease in photosynthate accumulation, and consequently the recession of plant growth. Except for habitat loss, individual plant reduction caused by deforestation could be responsible for the population decline of Cypripedium.

油蒿叶片氮分配对其最大净光合速率季节变异的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 油蒿叶片氮分配对其最大净光合速率季节变异的影响 DOI: 10.5846/stxb202107061799 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（32101588,32071842,32071843,31901366） Effects of leaf nitrogen allocation on seasonal variation in maximum net photosynthetic rate in Artemisia ordosica Author: Affiliation: Fund Project: Supported by the National Natural Science Foundation of China (32101588、32071842, 32071843 and 31901366) 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:植物最大净光合速率的季节变异性及其氮调控机制是近年来植物生理生态领域研究热点，对荒漠植物光合最大净光合速率季节动态及其叶氮影响，特别是叶氮分配对最大净光合速率调控机制的了解仍非常有限。2018年5-10月在宁夏盐池毛乌素沙地，对当地主要建群种油蒿(Artemisia ordosica)进行生长季原位观测，测定其叶光合光响应曲线(A-PAR)、CO2响应曲线(A-Ci)和叶氮含量，结合环境观测数据，分析A-PAR关键参数最大净光合速率(Amax)的季节变异和叶片氮分配相关参数对Amax的调控。结果表明，油蒿叶片Amax在生长期季节变异系数(Cv)为14%，在完全展叶中期，光合氮利用效率(PNUE)有最大值11.82 μmolCO2 gN-1 s-1，此时叶片氮素在光合系统中的分配比例最大，Amax有最大值29.48 μmol CO2 m-2s-1，油蒿光合能力较强。在完全展叶末期，油蒿叶片氮在光合系统中的分配比例(Pp)有最小值0.21，此时叶氮分配更倾向于非光合系统，Amax较小，光合能力较弱，有利于油蒿延长叶片寿命。Amax与单位干重叶片氮含量(Nmass)、氮在捕光系统中分配比例(PL)、氮在生物力能系统中分配比例(Pb)正相关(P<0.05)，其中，PL对Amax产生了最大的直接正向影响，氮在羧化系统中分配比例(Pc)主要通过Pb对Amax的产生了间接的正向影响，Pb对Amax季节动态的解释度最大(R2=0.49，P<0.01)。Amax与比叶重(LMA)负相关(P<0.05)，即当有较高LMA时油蒿具有较低的光合速率，此时叶片光合能力较弱，叶片机械韧性较强。不同物候时期，油蒿叶片氮素分配的变化及叶片光合能力与结构性状之间的权衡关系，标志着荒漠植物对其生境的适应性调节。研究结果不但可提高荒漠灌木油蒿生态系统生产力预测的准确性，也是对植物光合适应机理认识的补充和深入。 Abstract:The understanding on the seasonal dynamics of the maximum net photosynthetic rate (Amax) and its nitrogen regulation in desert plants has been a concern in plant ecology. Understanding of the dynamics of Amax and its nitrogen regulation, especially the effect of leaf nitrogen allocation on the regulation mechanism of Amax is unusually limited in desert plants. In order to elucidate the mechanism of the seasonal variation in Amax in a dominant desert shrub, Artemisia ordosica. Seasonal variation in Amax and the effect of leaf nitrogen allocation on Amax were analyzed through season-long in-situ measurements of the light response curve (A-PAR), CO2 response curve (A-Ci), leaf nitrogen along with simultaneously environmental measurements from May to October, 2018 in Mu Us Desert, Yanchi, Northwest China. As a result, Amax of Artemisia ordosica varied seasonally, being larger in the middle stage of leaf expansion, with a coefficient of variation (Cv) of 14%. The maximum value of photosynthetic nitrogen use efficiency (PNUE) was 11.82 μmolCO2 gN -1 s-1 in the middle stage of leaf expansion. At this time, the distribution proportion of leaf nitrogen in the photosynthetic system was the largest, and Amax had the maximum value of 29.48 μmol CO2 m-2s-1. At the end of complete leaf expansion, the distribution proportion of leaf nitrogen in photosynthetic system (Pp) had a minimum value of 0.21. At this phenological stage, the plants had smaller Amax and lower photosynthetic capacity, and leaf nitrogen distribution was more inclined to non-photosynthetic system, which was beneficial to extend the life of plant leaves. The Amax was positively related to nitrogen content (Nmass), nitrogen distribution in light capture system (PL), and nitrogen distribution in bioenergy system (Pb). PL had the greatest directly positive effect on Amax(P<0.05), nitrogen distribution in carboxylation system (Pc) had indirect positive effect on Amax mainly through Pb, and Pb had the greatest explanation for Amax seasonal dynamics (R2=0.49, P<0.01). Amax of Artemisia ordosica was negatively correlated with leaf mass per unit area (LMA) (P<0.05), indicating that there were higher LMA and lower photosynthetic capacity when leaf photosynthetic rate was lower, and the mechanical toughness of leaves was stronger. The trade-offs between the seasonal variation of leaf nitrogen allocation, and leaf photosynthetic capacity and leaf structure traits, indicated an acclimation of a desert plant to its environmental changes in different phenological periods. The results would contribute to more realistic and accurate prediction of ecosystem response to changing climate, and to deepen understanding of photosynthetic acclimation to biotic and abiotic factors. 参考文献 相似文献 引证文献

森林光环境对4种乔木幼树光合和光谱反射特性的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 森林光环境对4种乔木幼树光合和光谱反射特性的影响 DOI: 10.5846/stxb202105171289 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（31971650） Photosynthetic characteristics and spectral reflectance characteristics of four natural tree saplings under forest light environment Author: Affiliation: Fund Project: The National Natural Science Foundation of China (General Program, Key Program, Major Research Plan) 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:在林窗、林缘、林下3种自然光环境下，对吉林蛟河阔叶红松林常见树种拧筋槭、白牛槭、色木槭和红松的光合和光谱特性进行对比研究，以期从生理生态角度探讨它们对自然光环境的适应能力和响应机制。结果表明：4种乔木幼树叶片的光饱和点（LSP）和光补偿点（LCP）随着生长环境光强的下降而减小，林下各树种幼树LSP和LCP显著低于林窗内幼树（P<0.05）；除白牛槭外林下其他树种最大净光合效率（Pnmax）均显著小于林窗内幼树（P<0.05）；不同树种幼树表观量子效率（AQY）和暗呼吸速率（Rd）随光环境的变化并没有出现明显的变化规律，各环境间差异较小。除白牛槭外，其他树种幼树叶绿素归一化指数（Chl NDI）随环境光强的减少而增大，林下树种的光化学反射指数（PRI）普遍高于光条件更好环境下树种，说明林下幼树叶片叶绿素含量和光合速率大于其他光环境；各树种植物叶片水分指数（WI）在不同光环境之间存在显著差异，环境光强越大植物叶片WI越小，植物叶片水分浓度越小。林缘下3种槭属幼树结构不敏感植被光谱指数（SIPI）显著小于其他光环境（P<0.05），说明林缘下幼树受到相对较小的环境胁迫。林窗内，红松具有最高的LCP、LSP、Pnmax、Rd和PRI，说明红松具有较高的光合潜力，更加适应高光生长环境，3种槭属中，白牛槭拥有最高的Chl NDI和PRI值，表现出较好的适应性，说明红松和白牛槭能在林窗环境内较好更新并逐步占据林冠层。 Abstract:To explore the adaptability and response mechanism of plants to natural light environment from the perspective of physiology and ecology, we studied the photosynthetic and spectral characteristics of common tree species (Acer triflorum, Acer mandshuricum, Acer mono, and Pinus koraiensis) in Jilin Jiaohe broad-leaved Korean pine forest under three natural light environments (forest gap, forest edge, and understory). The results showed as follows:the light saturation point(LSP) and light compensation point(LCP) of saplings of the four tree species decreased with the decrease of ambient light intensity, and the LSP and LCP of saplings of all tree species were significantly lower than those of saplings in gap (P<0.05). Except Acer mandshuricum, The maximum net photosynthetic rate(Pnmax) of other tree species was significantly smaller than that of saplings in the gap(P<0.05). The apparent quantum yield(AQY) and dark respiration rate(Rd) of saplings of different tree species did not change significantly with the change of light environment, and there was little difference among different environments. The chlorophyll normalized index (Chl NDI) of sapling trees increased with the decrease of ambient light intensity except Acer mandshuricum. The photochemical reflectance index(PRI) value of understory trees was generally higher than that of trees under better light conditions, indicating that the chlorophyll content and photosynthetic rate of understory trees was higher than that of other light conditions. There were significant differences in the water index(WI)of leaves among different tree species in different light environments(P<0.05), and the WI of leaves decreased with the increase of environmental light intensity, showing that the water concentration of sapling leaves was the lowest under the gap environment.The structure-insensitive pigment index (SIPI) of three acer species at the forest edge was significantly lower than that of other light environments(P<0.05), indicating that the saplings under the forest edge were subjected to relatively little environmental stress.In the forest gap, Pinus koraiensis had the highest LCP, LSP, Pnmax, Rd and PRI, indicating that Pinus koraiensis had higher photosynthetic potential and was more adaptable to high-light growing environment. Among the three acer species, Acer mandshuricum had the highest Chl NDI and PRI values, indicating that it had good adaptability to the light environment in forest gap. These results indicated that Pinus koraiensis and Acer mandshuricum could renew well and occupy the canopy gradually in the gap environment. 参考文献 相似文献 引证文献

Effects of excessive nitrogen fertilizer and soil moisture deficiency on antioxidant enzyme system and osmotic adjustment in tomato seedlings

Long-term excessive application of nitrogen fertilizer induces secondary salinization of soil, which results in inhibiting plant growth. In addition, soil moisture deficiency also affects plant growth. To investigate the effects of excessive nitrogen fertilizer and soil moisture deficiency on the antioxidant enzyme system, plant water relations were analyzed through pressure-volume (P-V) curve, and photosynthetic light response parameters in tomato (Solanum lycopersicum L. Myoko) seedlings, an indoor experiment about 50 d was conducted using two irrigation water amounts based on field capacity (soil moisture deficiency: 50%-80%; adequate water: 70%-80%), two nitrogen fertilizer rates (moderate nitrogen; excessive nitrogen fertilizer: 0.585 g/pot) and two types of irrigation water (tap water and microbial diluent). The results showed that excessive nitrogen fertilizer (N) and soil moisture deficiency (W) reduced the biomass of tomato seedlings. In comparison to CK (combination of adequate water and tap water quality), microbial dilution (EM) increased plant biomass by 5.2%. Also, the nitrogen application increased chlorophyll relative contents (SPAD). The maximum net photosynthetic rate (Pc) decreased with nitrogen application and increased with EM application and irrigation amount. Excessive nitrogen application increased the plant nitrate reductase activity (NR). The plant NR in the N treatment showed a 13.0% increase compared to CK, and the plant NR in the treatment of nitrogen application with water deficiency (WN) increased 34.0% compared to water deficiency (W). After applying excessive nitrogen, N, EM-N, WN, EM-WN respectively increased the plant nitrate reductase activity by 13.0%, 22.9%, 34.0% and 28.6%, compared with the corresponding treatment with moderate nitrogen (i.e., CK, EM, W and EM-W). In addition, the activities of antioxidant enzymes [superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT)] in four treatments of nitrogen application (N, EM-N, WN, EM-WN) also increased significantly. Both soil moisture and nitrogen fertilizer significantly affect the parameters of osmotic adjustment, which is manifested in the reduction of osmotic potential (πFT), and the increase in the osmotic concentration (Cosm) and concentration difference (ΔCosm). But the decrease in the relative water content of apoplast (ζap), indicating that water deficiency and excessive nitrogen reduced the water absorption and water retention capacity of tomatoes to a certain extent. In conclusion, excessive nitrogen application and soil moisture deficiency inhibit plant growth significantly in this experiment. Meanwhile, microbial dilution can alleviate excessive nitrogen fertilizer and water stress to some extent, but the effect was not significant. Keywords: antioxidant enzyme, nitrogen, osmotic adjustment, pressure-volume curve, stress, tomato, water DOI: 10.25165/j.ijabe.20221502.5555 Citation: Zhang Y J, Yu S E, Li Z J, Chang T T, Xu Q C, Xu H L, et al. Effects of excessive nitrogen fertilizer and soil moisture deficiency on antioxidant enzyme system and osmotic adjustment in tomato seedlings. Int J Agric & Biol Eng, 2022; 15(2): 127–134.

Effects of photosynthetic models on the calculation results of photosynthetic response parameters in young Larix principis-rupprechtii Mayr. plantation.

Accurately predicting the crown photosynthesis of trees is necessary for better understanding the C circle in terrestrial ecosystem. However, modeling crown for individual tree is still challenging with the complex crown structure and changeable environmental conditions. This study was conducted to explore model in modeling the photosynthesis light response curve of the tree crown of young Larix principis-rupprechtii Mayr. Plantation. The rectangular hyperbolic model (RHM), non-rectangular hyperbolic model (NRHM), exponential model (EM) and modified rectangular hyperbolic model (MRHM) were used to model the photosynthetic light response curves. The fitting accuracy of these models was tested by comparing determinants coefficients (R2), mean square errors (MSE) and Akaike information criterion (AIC). The results showed that the mean value of R2 of MRHM (R2 = 0.9687) was the highest, whereas MSE value (MSE = 0.0748) and AIC value (AIC = -39.21) were the lowest. The order of fitting accuracy of the four models for Pn-PAR response curve was as follows: MRHM > EM > NRHM > RHM. In addition, the light saturation point (LSP) obtained by MRHM was slightly lower than the observed values, whereas the maximum net photosynthetic rates (Pmax) modeled by the four models were close to the measured values. Therefore, MRHM was superior to other three models in describing the photosynthetic response curve, the accurate values were that the quantum efficiency (α), maximum net photosynthetic rate (Pmax), light saturation point (LSP), light compensation point (LCP) and respiration rate (Rd) were 0.06, 6.06 μmol·m-2s-1, 802.68 μmol·m-2s-1, 10.76 μmol·m-2s-1 and 0.60 μmol·m-2s-1. Moreover, the photosynthetic response parameters values among different layers were also significant. Our findings have critical implications for parameter calibration of photosynthetic models and thus robust prediction of photosynthetic response in forests.

Effects of Soil Nitrogen Addition on Crown CO2 Exchange of Fraxinus mandshurica Rupr. Saplings

The impact of atmospheric nitrogen deposition on carbon exchange between forest and atmosphere is one of the research hotspots of global change ecology, past researchers have extensively studied the impacts on leaf level, while the impacts on crown CO2 exchange are still unclear. Therefore, we explored the impacts of different nitrogen addition levels on crown CO2 exchange of Fraxinus mandshurica saplings and their responses to the changes of major meteorological factors (photosynthetically active radiation, PAR; vapor pressure deficiency, VPD; and air temperature, Tair) with a novel automated chamber system. There are four levels of nitrogen addition treatments: control (no nitrogen addition, CK), 23 (low nitrogen addition, LN), 46 (medium nitrogen addition, MN), and 69 kgN·hm−2·a−1 (high nitrogen addition, HN). Our results showed that all nitrogen addition treatments increased daily average and accumulated gross primary production (GPP), crown respiration (R), and net crown CO2 exchange (Ne), especially at medium and high nitrogen levels. Similarly, maximum net photosynthetic rate (Nemax) and apparent quantum efficiency (α) were promoted. The change of Ne with PAR, Tair, and VPD showed that nitrogen addition postponed the appearance of photosynthesis midday depression. In addition, the monthly accumulation of R with all nitrogen addition treatments showed an increasing trend (June to July), and then decreased (July to September) during the growing season, while the Ne and GPP decreased gradually with seasonal vegetation senescence. Finally, the crown shifted from carbon sink to carbon source at the end of the growing season, however, the change under high nitrogen treatment occurred 3 days later. The crown CO2 exchange measurements provide a new perspective to better understand the response of forest ecosystem CO2 exchange to elevated nitrogen deposition and provide a basis for related carbon model parameter correction under the influence of nitrogen deposition.

Effects of arbuscular mycorrhizal fungi on the nitrogen distribution in endangered Torreya jackii under nitrogen limitation.

Arbuscular mycorrhizal fungi regulated the distribution of nitrogen in the leaves, thereby facilitating the adaptation of the endangered plant Torreya jackii to a low-nitrogen environment. Rhizophagus irregularis was inoculated into sterilized soil to investigate its impact on the distribution ratio of leaf nitrogen in cell wall proteins, cell membrane proteins, water-soluble proteins, and photosynthetic systems which includes the carboxylation system (PC), energy metabolism (PB), and light-harvesting system in the endangered species Torreya jackii. The results showed that R. irregularis reduced the specific leaf weight and the distribution ratio of nitrogen in cell wall proteins in the leaves of T. jackii, whereas it enhanced the distribution ratio of nitrogen in cell membrane proteins and water-soluble proteins. R. irregularis enabled more nitrogen uptake for growth by decreasing the distribution of nitrogen to the structural substances. At low-nitrogen levels, inoculation with R. irregularis improved the plant height (18.78 ~ 36.04%), shoot dry weight (50.53 ~ 64.33%), total dry weight (42.86 ~ 52.82%), maximal net photosynthetic rate (Pmax) (16.83 ~ 20.11%), photosynthetic nitrogen use efficiency (PNUE) (40.01 ~ 43.14%), PC (33.56 ~ 38.59%) and PB (29.08 ~ 34.02%). However, it did not substantially affect the leaf nitrogen content per unit area or the leaf nitrogen content per unit mass. Moreover, Pmax exhibited a significant positive correlation with PC and PB, and all three parameters showed a significant positive correlation with the PNUE, thereby revealing that R. irregularis increased the photosynthetic capacity and PNUE of T. jackii through boosting PC and PB.

Succinic acid inhibits photosynthesis of Microcystis aeruginosa via damaging PSII oxygen-evolving complex and reaction center.

To elucidate the mechanism of succinic acid (SA) inhibition of Microcystis aeruginosa, the chlorophyll fluorescence transients, photosynthesis, photosynthetic electron transport activity, and gene expression of M. aeruginosa were evaluated under various doses of SA. The results demonstrated that, after treatment with 60 mg L-1 SA for 1 h, the chlorophyll fluorescence transients and related parameters changed significantly, indicating that the function and structure of photosynthetic apparatuses of Microcystis were seriously damaged. The initial quantum efficiency α, maximum net photosynthetic rate Pnmax, dark respiration rate Rd, and gross photosynthetic rate decreased to 57%, 49%, 49%, and 46%, respectively, relative to the control. Furthermore, photosystem II (PSII) activity (H2O→p-BQ) and the electron transport activity of H2O→MV and DPC→MV significantly decreased. Real-time PCR analysis revealed that, following incubation with 60 mg L-1 SA for 24 h, the expression level of core protein genes (psbA, psaB, psbD, and psbO) of the photosynthesis centers photosystem I (PSI) and PSII decreased significantly. However, the transcription of gene nblA encoding phycobilisome degradation protein was elevated. The downregulation of the rbcL gene, which encodes the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), resulted in the suppression of CO2 fixation and assimilation. High concentration (60 mg L-1) of SA resulted in damage to oxygen-evolving complex (OEC) and reaction center of PSII, blocking photosynthetic electron transport, thereby lowering the rate photosynthesis and inhibiting the growth of Microcystis. We concluded that inhibition of photosynthesis is an important mechanism of SA inhibition in M. aeruginosa.