Photosynthetic Index Research Articles

Apple and maize physiological characteristics and water-use efficiency in an alley cropping system under water and fertilizer coupling in Loess Plateau, China

Water, nutrient and light deficiency during the co-growth period are the major factors limiting the productivity of the apple–maize alley cropping system in Loess Plateau, China. Therefore, it is crucial to optimize the management of water and fertilizer in the region. The effects of different irrigation and fertilizer levels on photosynthetic characteristics, growth, yield, water consumption (ET) and water use efficiency were studied in a young apple-maize intercropping system during 2014–2016. The treatments included three levels of maximum irrigation, namely 50% (W1), 65% (W2), and 85% (W3) of field capacity (Fc), and three different NPK fertilization levels (289.0-118.0-118.0, 412.4-168.8-168.8 and 537.0-219.0-219.0 kg∙ha−1), which were designated F1, F2 and F3, respectively. In addition, the rain-fed (neither irrigation nor fertilizer) crop was included as the control (CK). The F1 significantly increased the net rate of photosynthesis (Pn) and leaf water-use efficiency (LWUE) of both apple and maize. For maize, the effect of irrigation was greater than that of fertilizers on water use, but smaller on growth indicators and yield. The ET of the alley cropping systems increased with the amount of irrigation but decreased as the dose of fertilizers increased. Growth and yield of maize increased when the amount of irrigation increased, but were inversely related to fertilizer dose. The canopy architecture appeared to be regulated through differential absorption of water and nutrients. The Pn and transpiration (Tr) in maize decreased as the distance from the tree line increased, and the extent of decrease grew over time, suggesting greater interspecific competition. It is recommended that dwarf crops should be planted after intercropping for 5 years according to the change in photosynthetic index with intercropping years under different treatments. Multiple regression analysis indicated the following regime to be optimal during the first 3–5 years of the intercropping in terms of the yield of maize and water use in the alley cropping system: maximum watering (85% Fc) and minimum fertilization (289.0-118.0-118.0 kg ha−1 NPK).

Evaluation of Suitable Amount of Water and Fertilizer for Mature Grapes in Drip Irrigation in Extreme Arid Regions

Low water and fertilizer use efficiency have become important factors restricting the sustainable development of agriculture in extreme arid areas, typically like Xinjiang in China. In order to optimize the water and fertilizer management system of grape drip irrigation in the region, field experiments were carried out to study the effects of different water and fertilizer treatments on the physiological growth, yield, and quality of grapes. Meanwhile, principal component analysis, grey correlation analysis, and regression analysis were used to quantify the relative optimal amount of water and fertilizer. The results showed that the effects of water and fertilizer interaction on the photosynthetic index and fluorescence index of grape leaves, in different growth periods, ng reached extremely significant levels (p < 0.01). The physiological indicators showed regular changes with the increase and decrease of water and fertilizer use and the appropriate amount of water and fertilizer could maintain the index at a superior level. Meanwhile, there are differences in the index of different growth stages and regular changes with the growth period. The effects of water and fertilizer interaction on the yield, water use efficiency, and quality of drip irrigation reached a very significant level (p < 0.01). The yield reached the maximum in W3F2 treatment and the yield increased by 29.76% compared with the minimum yield of W1F1. The quality index reached a superior level in W3F2 treatment. The results of principal component analysis and grey correlation analysis showed that the optimal water and fertilizer dosage was W3F2 (irrigation 750 mm, fertilization 750 kg ha−1), of which N (300 kg ha−1)-P2O5 (150 kg ha−1)-K2O (300 kg ha−1), and multiple regression analysis was employed to determine the optimal range of water and fertilizer use is the following: Irrigation volume 725–825 mm and fertilization amount 684–889 kg ha−1, of which N (273.6–355.6 kg ha−1) - P2O5 (136.8–177.8 kg ha−1) - K2O (273.6–355.6 kg ha−1). The research results can provide a scientific basis for the water and fertilizer management and drip irrigation technology of drip irrigation in seedless white grape fields in extremely arid areas and it is of great significance for the efficient use of regional water and fertilizer resources and the realization of sustainable socio-economic development in the region.

Combined Effect of Different Amounts of Irrigation and Mulch Films on Physiological Indexes and Yield of Drip-Irrigated Maize (Zea mays L.)

Exploring the effect of irrigation on biodegradable film-covered drip-irrigated maize is essential for sustainable agricultural development in arid areas. These regions, like Xinjiang in China, are home to suitable irrigation and biodegradable films. Through field trials, four levels of irrigation, and two biodegradable films and one common polyethylene film were set up to study the effects of different treatments on the physiology, growth indicators, and yield of maize. The results showed that the effects of irrigation and biodegradable films on the photosynthetic index and fluorescence index of maize reached a very significant level (p < 0.01). The effect of single factor irrigation and biodegradable films on the photosynthetic index and fluorescence index of maize reached a significant level (p < 0.05). The photosynthesis index, fluorescence index, plant height, LAI (leaf area index) and yield of W3M3 treatment had the highest value, when compared with other treatments. The W1M1 treatment had the lowest value. The photosynthesis index, fluorescence index, plant height, LAI, and yield of the W3M2 treatment were second only to W3M3. In addition, the output was only 40 kg ha−1 less than W3M3. W3M2 has the best treatment effect from a perspective of sustainable agricultural development and efficient water saving; the optimal irrigation amount was 5625 m3 ha−1, induction period was 60 d, and thickness was 0.01 mm. The results of this study are of guiding significance for the promotion of the use of biodegradable films, search for suitable irrigation, and development of low-carbon agriculture.

Physiological and Transcriptome Analyses of Early Leaf Senescence for ospls1 Mutant Rice (Oryza sativa L.) during the Grain-Filling Stage.

Early leaf senescence is an important agronomic trait that affects crop yield and quality. To understand the molecular mechanism of early leaf senescence, Oryza sativa premature leaf senescence 1 (ospls1) mutant rice with a deletion of OsVHA-A and its wild type were employed in this study. The genotype-dependent differences in photosynthetic indexes, senescence-related physiological parameters, and yield characters were investigated during the grain-filling stage. Moreover, RNA sequencing (RNA-seq) was performed to determine the genotype differences in transcriptome during the grain-filling stage. Results showed that the ospls1 mutant underwent significant decreases in the maximal quantum yield of photosystem II (PSII) photochemistry (Fv/Fm), net photosynthesis rate (Pn), and soluble sugar and protein, followed by the decreases in OsVHA-A transcript and vacuolar H+-ATPase activity. Finally, yield traits were severely suppressed in the ospls1 mutant. RNA-seq results showed that 4827 differentially expressed genes (DEGs) were identified in ospls1 mutant between 0 day and 14 days, and the pathways of biosynthesis of secondary metabolites, carbon fixation in photosynthetic organisms, and photosynthesis were downregulated in the senescing leaves of ospls1 mutant during the grain-filling stage. In addition, 81 differentially expressed TFs were identified to be involved in leaf senescence. Eleven DEGs related to hormone signaling pathways were significantly enriched in auxin, cytokinins, brassinosteroids, and abscisic acid pathways, indicating that hormone signaling pathways participated in leaf senescence. Some antioxidative and carbohydrate metabolism-related genes were detected to be differentially expressed in the senescing leaves of ospls1 mutant, suggesting that these genes probably play response and regulatory roles in leaf senescence.

The Effects of Saline Stress on the Growth of Two Shrub Species in the Qaidam Basin of Northwestern China

Soil salinization is a serious issue in the Qaidam Basin and significantly limits economic development. To explore the salt tolerance of two shrubs in this area, we determined several parameters, including the Soil and Plant Analyzer Development (SPAD), net photosynthetic rate (Pn), transpiration rate (Tr), intercellular carbon dioxide (Ci, μmol mol−1), stomatal conductance (Gs, umol m−2s−1), and water use efficiency (WUE) under different salt concentrations (0, 100, 200, 300, and 400 mmol·L−1). In addition, the shrubs of Elaeagnus angustifolia and Lycium barbarum of salt tolerance were evaluated. The photosynthetic parameters of E. angustifolia were more sensitive to salinity than those of L. barbarum, and SPAD, Pn, Tr, and WUE of E. angustifolia decreased significantly with increasing salt concentrations (p < 0.05), while in L. barbarum, SPAD, Pn, and Tr decreased significantly with increasing salt concentrations (p < 0.05), but the WUE of L. barbarum showed no significantly variation under the salt concentration gradient. The results of correlation matrix of photosynthetic index also indicated that the minimum salt tolerance of E. angustifolia and L. barbarum were 108.4 and 246.3 mmol·L−1, respectively. Our results provide a scientific basis for the selection of salt-tolerant plant species in of northwest China.

Evaluating the salt tolerance of seven fig cultivars (Ficus carica L.)

The growing demand for both fresh and dry figs worldwide is due to its richness in mineral compounds (i.e. iron and copper) and polyphenols. Considering the position of Iranian cultivars in global fig market, the present study examined the growth and photosynthetic rate of commercial fig cultivars (i.e. ‘Sabzʼ, ‘Siyahʼ, ‘Shah Anjirʼ, ‘Atabakiʼ, ‘Kashkiʼ, ‘Matiʼ and ‘Bar Anjirʼ) exposed to six salt treatments corresponding to the following electrical conductivities (EC): 0.5, 2, 4, 6, 8 and 10 dSm-1. The results indicated a decrease trend of stem length, stem diameter and leaf number in salt-exposed plants. The electrolyte leakage and protein content in all cultivars followed an ascending trend. The specific leaf area, relative water content, photosynthetic indices and nitrogen content followed a decreasing trend according with increasing salinity. The ‘Siyahʼ and ‘Sabzʼ, as the most salt-tolerant cultivars, had the maximum leaf abscission, the lowest transpiration rate and leaf water content under salt condition, compared to all other tested cultivars. Moreover, they had the most leaf succulence and leaf dry matter content and the lowest specific leaf area, which related to the balance between growth ratio and osmotic regulation under salt conditions. The ‘Shah Anjirʼ, as the most salt-sensitive cultivar, could not balance transpiration rate and leaf water content under salt treatment higher than 4 dSm-1.

不同生态型芦苇种群对盐胁迫的生长和光合特性

PDF HTML阅读 XML下载 导出引用 引用提醒 不同生态型芦苇种群对盐胁迫的生长和光合特性 DOI: 10.5846/stxb201712082209 作者: 作者单位: 山东大学生命科学学院,山东大学生命科学学院,山东大学生命科学学院,山东大学生命科学学院,山东大学生命科学学院;青岛农业大学园林与林学院,Department of Bioscience,Plant Biology,Aarhus University,Ole Worms Alle ,Aarhus C DK-,Denmark;Department of Bioscience,Plant Biology,Aarhus University,Ole Worms Alle ,Aarhus C DK-,Denmark,Department of Bioscience,Plant Biology,Aarhus University,Ole Worms Alle ,Aarhus C DK-,Denmark;Department of Bioscience,Plant Biology,Aarhus University,Ole Worms Alle ,Aarhus C DK-,Denmark,山东大学生命科学学院,山东大学生命科学学院,山东大学生命科学学院 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（31770361，31470402）；山东省自然科学基金中青年科学家科研奖励基金项目（BS2015HZ020）；山东大学国家级大学生创新创业项目（201710422026） Different adaptions of physiological ecology between estuarine and landlocked reeds in different salinities Author: Affiliation: School of Life Science, Shandong University,,,,,,,,,Shandong University Fund Project: 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:土壤盐渍化是影响我国土壤利用效率的主要因素之一，芦苇是改良土壤盐渍化的良好实验材料，但芦苇有着多种的生态型，比较各生态型芦苇的耐盐差异成为亟待解决的问题。通过设置淡水（0.00%）与加盐（质量浓度2.00%）处理控制实验，测量芦苇的生长指标和光合指标，比较河口型芦苇与内陆型芦苇耐盐性，寻找合适生态型的芦苇作为改良土壤盐渍化的生物材料。在实验中，与淡水条件相比，加盐（2.00%）处理条件下，河口型芦苇和内陆型芦苇的株高（height）、蒸腾速率（E）均显著性下降，但是两种生态型的芦苇的水分利用效率（WUE）明显提高；河口型的芦苇相对生长速率（RGR）和气孔导度（Gs）都明显高于内陆型芦苇。在淡水环境中，河口型芦苇的相对生长速率（RGR）和净光合速率（A）都显著性地高于内陆型芦苇。结果表明两种生态型的芦苇在进化过程中存在一定程度上的分化，盐胁迫会抑制两种芦苇的生长，两种生态型芦苇的相对生长速率和气孔导度在盐胁迫下出现明显地差异，表明两种生态型的芦苇对盐度的响应机制有所差异。相比于内陆型芦苇，河口型芦苇有着更强的耐盐性，内陆型及河口型芦苇的表型性状差异主要是由于其原生境的差异所决定的。 Abstract:Soil salinization is one of the main factors affecting soil use efficiency in China. Phragmites australis is a good experimental material for improving soil salinization. Phragmites australis has a variety of ecotypes, and determination of salt tolerance differences among ecotypes of Phragmites australis is an urgent problem to be solved. By setting up freshwater and saltwater treatments, and measuring the growth index and photosynthetic index of Phragmites australis in both, an experiment was conducted to compare the salinity of estuarine reeds and landlocked reeds, and to find biological material to combat soil salinization. Compared with the freshwater treatment, the height and transpiration rate (E) of landlocked reeds significantly decreased under the condition of salt addition, but the water use efficiency (WUE) of both ecotypes significantly increased. The relative growth rate (RGR) and stomatal conductance (Gs) of estuarine reeds were significantly higher than those of inland reeds. In the freshwater environment, the relative growth rate (RGR) and net photosynthetic rate (A) of estuarine reeds were significantly higher than those of inland reeds. The results showed that there was a certain degree of differentiation between the two ecotypes of reeds during the evolutionary process and that salt stress inhibited the growth of both ecotypes. The relative growth rate (RGR) and stomatal conductance (Gs) of the two ecotypes of reed showed significant differences under salt stress, which indicates that the responses of the two ecotypes to salinity are different. In comparison to inland reeds, estuarine reeds are more resistant to salt stress. The differences in phenotypic traits of inland and estuarine reeds are mainly determined by the differences in their in situ habitats. 参考文献 相似文献 引证文献

Responses of leaf-associated biofilms on the submerged macrophyte Vallisneria natans during harmful algal blooms

The present study investigated the physiological responses, photosynthetic activity, and microbial community structure of leaf-associated biofilms on the microphyte Vallisneria natans during a harmful algal bloom. Results of the physiological and photosynthetic indices (Fv/Fm ratios [maximum quantum yield of photosystem II (PSII)]; malondialdehyde content; total chlorophyll; and activities of superoxide dismutase, catalase and peroxidase) indicated that algal blooms could cause inhibition of photosynthesis, oxidative stress and an antioxidant system stress response in Vallisneria natans leaf-associated biofilms. Multifractal analysis suggested that allelochemicals or algal organic matter released by cyanobacteria could reduce the surface roughness of the leaf. Microbial diversity analysis of the biofilms showed that algal blooms slightly altered the microbial community structure while the richness and evenness of the microbial composition remained stable. This study provided useful information to better understand the adverse effects of algal blooms on submerged macrophytes.

Effects of grafting and gradual rootstock substitution on gas exchanges of orange seedlings under high atmospheric evaporative demand

Interstocked seedlings are produced by making two successive grafts. In one of the methods used, interstocked seedlings can be produced by introducing a rootstock by inarching and a scion by budding in a previously formed seminiferous seedling. The hypothesis of the present research is that double grafting may reduce shoot hydraulic conductivity and reduce water supply to the scion, affecting leaf gas exchanges and photochemical efficiency. Thus, in the present study the effect was assessed of sequential grafting (inarching and budding) during the production process of interstocked ‘Pêra’ sweet orange plants on their net photosynthesis and growth capacity. The grafts were made on ‘Seleta’ (S) sweet orange or Rangpur lime (R) nucellar seedlings. First the seedlings were inarched with Poncirus trifoliata var. monstrosa ‘Flying Dragon’ (FD) and in the second stage, they were budding with ‘Pêra’ orange (P), to form the scion. A completely randomized design was used, with three treatments, seven replications and one plant per plot. The treatments consisted of the following combinations between scion, interstock and rootstock: P/S/FD; P/R/FD and P/R, and the latter combination was used as control. At 390 days after sowing, the seedlings had two functional root systems and their height and diameter were measured. The net CO2 assimilation rate (A), stomatal conductance (gs), transpiration (E), internal CO2 concentration in mesophyll (Ci), maximum quantum efficiency of Photosystem II (Fv/Fm), photosynthetic index (Pi), leaf temperature (°C) at 8:00 and 13:00 and the SPAD reading were determined on the leaves. The seedlings did not differ in its height or in diameter of their inarch. Among the seedlings with double rootstocks, higher diameter was observed in the ‘Seleta’ sweet orange stem. The connections in the plant, caused by inarching and budding, and the gradual rootstock substitution, made these plants more sensitive to high atmospheric evaporative demand during nursery stage, and reduced photosynthetic carbon assimilation.

Low salinity promotes the growth of broccoli sprouts by regulating hormonal homeostasis and photosynthesis

Broccoli sprouts produce several bioactive compounds and are recognized as a health-promoting vegetable. In this study, the effect of salinity (NaCl) on the growth of broccoli sprouts was investigated. Broccoli seeds were germinated for 4 and 8 d with spraying 0–120 mM NaCl and then harvested to evaluate changes in endogenous hormones, photosynthetic indices, chlorophyll fluorescence parameters and chloroplast ultrastructure. The growth of sprouts was significantly promoted by low salinity (40 and 80 mM NaCl) and inhibited by high salinity treatment (120, 160 and 200 mM NaCl). In 8-day-old sprouts treated with 80 mM NaCl, levels of abscisic acid, cytokinin, brassinolide, indole-3-acetic acid and gibberellic acid were significantly enhanced, while net photosynthetic rate increased in low salinity conditions was due to the elevated chlorophyll content and increased photosystem II activity. Furthermore, low salinity increased the leaf area maximally in both 4- and 8-day-old sprouts. Enlarged chloroplast and an increased number of grana also contributed to improved photosynthesis. Low salinity conditions induced endogenous growth hormone synthesis and improved photosynthesis, thereby promoting the growth of broccoli sprouts. This study provides a theoretical basis for the improved production of broccoli sprouts in low salinity conditions.

Allelopathic effects of harmful algal extracts and exudates on biofilms on leaves of Vallisneria natans

This study investigated the allelopathic effects of Microcystis aeruginosa (M. aeruginosa) extracts and exudates on the physiological responses, photosynthetic activity, and microbial structure of biofilms on leaves of Vallisneria natans (V. natans). By measuring physiological and photosynthetic indices, the results showed that M. aeruginosa allelochemicals inhibited photosynthesis, oxidative stress and antioxidant system stress response in the biofilms of V. natans leaves. Multifractal analysis found that the surface topography of V. natans leaves was altered due to the allelochemicals found in M. aeruginosa. Microbial diversity on the leaves was analyzed using high-throughput sequencing, and the results showed that M. aeruginosa exudates had a stronger effects on the microbial community structure of biofilms compared to extracts. These findings highlight how cyanobacterial allelochemicals induce negative effects on submerged macrophytes.

Effect of Epichloë gansuensis endophyte on the activity of enzymes of nitrogen metabolism, nitrogen use efficiency and photosynthetic ability of Achnatherum inebrians under various NaCl concentrations

This study explored the effects of Epichloe gansuensis endophyte on photosynthetic ability, the activity of nitrogen metabolism enzymes, nitrogen use efficiency, and biomass accumulation of Achnatherum inebrians growing under five NaCl concentrations. A. inebrians plants with (E+) and without E. gansuensis (E−) were grown under different NaCl concentrations. Photosynthetic indexes, NO3− and NH4+ content, nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS) activity, nitrogen use efficiency and nitrogen content were determined. The plant total biomass, NO3− and N content, NR, NiR and GS activity, total N accumulation (TNA), nitrogen utilization efficiency (NUtE) and nitrogen uptake efficiency (NUpE) were higher in leaves and roots of E+ than of E− plants under 300 and 400 mM NaCl concentrations, but NH4+ content was lower in leaves and roots of E+ than of E− plants under 100, 200, 300 and 400 mM NaCl concentrations. However, there were almost no significant effects on these factors between E+ and E− plants under the 0 mM NaCl concentration. The endophyte improved the growth of plants under high NaCl concentration by improving photosynthetic ability, increasing the activity of nitrogen metabolism enzymes and nitrogen use efficiency.

Increased tolerance to organic xenobiotics following recent allopolyploidy in Spartina (Poaceae)

Genome doubling or polyploidy is a widespread phenomenon in plants where it has important evolutionary consequences affecting the species distribution and ecology. PAHs are ubiquitous organic pollutants, which represent a major environmental concern. Recent data showed that tolerance to organic xenobiotics involve specific signaling pathways, and detoxifying gene sets referred as ‘the xenome’. However, no data are available about how polyploidy impacts tolerance to organic xenobiotics. In the present paper, we investigated PAH tolerance following allopolyploidization in Spartina alterniflora, S. maritima and their derived allopolyploid species S. anglica. We performed comparative analyses of cellular compartmentalization, photosynthetic indices, and oxidative stress markers under phenanthrene-induced stress, and found that S. anglica exhibit increased tolerance compared to its parents. Based on 52 genes potentially involved in phenanthrene detoxification previously identified in A. thaliana, we investigated the Spartina xenome using genomic and transcriptomic available resources. Subsequently, we focused on GSTs, a ubiquitous enzymes class involved in organic xenobiotic detoxification. We examined expression profiles of selected genes by RT-qPCR, and revealed various patterns of parental expression alteration in the allopolyploid. The impacts of allopolyploidization on phenanthrene-induced stress and their potential ecological implications are discussed. The neo-allopolyploid S. anglica appears as a potential candidate for phytoremediation in PAH-polluted marshes.

One-step approach for estimating maize actual water use: Part I. Modeling a variable surface resistance

In a global scenario of climate change, water scarcity and population growth, it is imperative to optimize crop water management. One way is by calibrating a physically based crop evapotranspiration (ET) model, in the so-called one-step approach; as opposed to the two-step approach that uses reference evapotranspiration and crop coefficients. The Penman–Monteith (Symposium of the society for experimental biology, the state and movement of water in living organisms, Academic Press, Inc., New York; Monteith, Symposium of the society for experimental biology, the state and movement of water in living organisms, Academic Press, Inc., New York, 1965) ET model uses a bulk surface resistance (rs) term. This variable describes the resistance (stomatal, leaf, and canopy) to crop water transpiration and water evaporation from the soil surface. If the crop is not transpiring at a potential rate the rs resistance depends on the water status of the soil and vegetation. The stomatal resistance is influenced by climate and by water availability. However, this influence is different from crop to crop. The resistance increases when the crop is stressed and when the soil water availability limits ET. In this study, surface resistance was parameterized for grain maize considering a number of plant and environmental variables for water stressed and non-stressed conditions. The independent explanatory variables that facilitated a good calibration of rs, on a half-hourly basis, were: net radiation, photosynthetic active radiation, aerodynamic resistance, crop height, and leaf area index. The application of the obtained “rs” model (based on the variables mentioned above) resulted in maize ET (mm 30-min−1) estimation error of less than 1 ± 10% when evaluated with eddy covariance based ET data. This result is evidence that it is possible to calculate maize ET with a small associated error at very small time scales, for water deprived and advective conditions, using the one-step ET approach.

Physiological Characteristics of Trees Recommended for the Phytoremediation of Soils Contaminated with Herbicides

ABSTRACT: Herbicides are inputs with a high volume of use in agricultural production systems for weed management; however, the environmental contamination they cause is a reality. The objective of this research was to evaluate the tolerance of tree species used for the phytoremediation of herbicides in the soil, to atrazine, clomazone and 2,4-D, through the evaluation of photosynthetic indices. Thus, a randomized block design experiment was conducted with four replications, in a 4 x 5 factorial arrangement, where the first factor represented the herbicides atrazine, clomazone and 2,4-D and the control treatment without herbicide (water). The second factor consisted in the use of pre-selected tree species for the phytoremediation of soils with residues of the products [Eremanthus crotonoides DC. (candeia), - Richeria grandis Vahl (richeria), Protium heptaphyllum (Aubl) Marchand, (breu-branco) Kielmeyera latrophyton Saddi, Kew Bull, (pau-santo) Calophyllum brasiliense Cambess (guanandi)]. The herbicides were applied through dishes placed under the culture containers of the plants, when they presented eight months of development. After 15 days from the herbicide application, the visual intoxication, stomatal conductance (Gs), transpiration rate (E), CO2 concentration in the substomatal chamber (Ci), and water use efficiency (WUE) were evaluated. The herbicides affected differently the physiological characteristics of the tree species; atrazine was the most harmful product. Individuals under the effect of 2,4-D and clomazone presented lower variation for their physiological characteristics, compared to the respective control treatments. Breu-branco, despite showing low visual intoxication provided by the herbicides, was the most affected species by the products. On the other hand, candeia was the most tolerant species to the action of the herbicides.

Influence of short periods of increased water temperature on species composition and photosynthetic activity in the Baltic periphyton communities

Periphyton plays a vital ecological role in shallow, well-lit ecosystems which are vulnerable to rapidly changing environmental conditions, including raising temperature due to global warming. Nevertheless, little is known on the effect of increased temperatures on the taxonomic structure and functioning of periphytic communities. In this study, the influence of short-term temperature increase on the species composition and photosynthetic activity of the Baltic periphytic communities was investigated. The collected communities were exposed to increased temperature of 23 °C (ca. 4 °C above the summer average) for 72 h. After this time, species composition of the communities was studied under light microscope and their photosynthetic performance was evaluated using PAM fluorometry. Results showed that the biomass of cyanobacteria slightly increased. There were significant changes in the abundance of diatom species, among which Fragilaria fasciculata and Navicula ramosissima, were negatively affected by the elevated temperature and their cell number significantly decreased, whereas, Diatoma moniliformis and N. perminuta were stimulated by the increased temperature. Additionally, a shift towards higher abundance of smaller taxa was also observed. The higher quantum yield of photosystem II (PSII) (higher ΦPSII) accompanied by the lower value of non-photochemical quenching (NPQ) observed in communities kept at 23 °C showed more efficient photosynthesis. This was further confirmed by the changes in rapid light curves (higher photosynthetic capacity, rETRmax, and photoacclimation index, Ek). The obtained data constitute evidence that short periods of increased temperature significantly affect the structure and functioning of the Baltic periphyton.

Growth Responses and Photosynthetic Indices of Bamboo Plant (Indocalamus latifolius) under Heavy Metal Stress.

Investigating factors involved in the alleviation of the toxic effects of heavy metals (HMs) on plants is regarded as one of the important research concerns in the environmental field. The southern regions of China are severely impacted by human-induced heavy metal (HM) contamination, which poses an impediment to growth and productivity of bamboo (Indocalamus latifolius) plants. This necessitates the investigation of the effects of HMs on growth and physiological properties of bamboo. Therefore, the aim of the study was to evaluate some gas exchange and growth parameters in two-year-old bamboo species under HMs stress. A greenhouse-based experiment was conducted at Nanjing Forestry University, where the bamboo plant was treated with three HMs (Cu, Pb, and Zn) at four different concentrations (0, 500, 1000, and 2000 mg kg-1). The results illustrated that excessive HMs (1000 and 2000 mg kg−1) triggered a decline in a number of photosynthetic-related indices including the rate of photosynthesis (μmol CO2 m−2 s−1), intercellular CO2 concentration (μmol CO2 mol−1), conductance to H2O (mol H2O m−2 s−1), and net assimilation as well as transpiration. Morphological indices were also depressed as a result of the adverse influence of HMs, leading to decreased shoot length (10 to 73%) and reduced number of emerged plants (6 to 57%). Also, the results indicated that Pb had the greatest harmful impact on the growth indices.

Linking photosynthetic performances with the changes in cover degree of three Mediterranean shrubs under climate manipulation

Understanding how different combinations of plant functional traits contribute to species fitness is a question of considerable ecological interest, that can give insights into the mechanisms controlling community assembly, and into the processes by which climate change can modify plant community structure and composition. We investigated the changes in cover degree of three shrubs (Cistus monspeliensis, Dorycnium pentaphyllum and Helichrysum microphyllum) growing in a Mediterranean garrigue subjected for 11 years to a reduced rainfall regime, following a conceptual framework based on the two‐phase resource dynamic model: considering the seasonal drought typical of the Mediterranean climate, the two‐phases were identified based on high (pulse phase) and low (interpulse phase) soil water availability. We developed a parameter proportional to the whole plant photosynthesis (plant photosynthetic index, PPI), scaling up the leaf photosynthesis to canopy level, taking into account the different canopy densities and the fluctuations in leaf biomass due to summer leaf shedding. PPI was used to derive plant performance estimators for both pulse (maximum value reached by PPI, PPImax) and interpulse phase (duration of the exhaustion phase, Durep, when drought constrains PPI below the plant carbon compensation point determining carbon starvation). For each species the ratio between PPImax and Durep (named PPIred) was used as an index of plant performance. The reduced rainfall regime mainly decreased the performances of the dominant species C. monspeliensis, both limiting PPImax and extending Durep. Under both natural and the manipulated rainfall regime, PPIred was proportional to plant success, measured as the cover degree variation rate of the species. This result suggests that a mechanistic approach using functional traits to quantify the different performance of co‐occurring species can be used to investigate 1) the drivers of the medium‐term changes in species abundance and 2) the processes responsible for change in plant community composition under climate change.

Overexpression of a novel transcriptional repressor GmMYB3a negatively regulates salt–alkali tolerance and stress-related genes in soybean

Myeloblastosis (MYB) transcription factor (TF) plays a positive role in the growth and stress response of plants; however, information on the functions of MYB repressors in soybean is limited. In the present study, the gene GmMYB3a was identified and characterized as a member of the R2R3 MYB repressor family, which is induced by various abiotic stresses. To understand the functions of GmMYB3a, a transgenic soybean over-expressing GmMYB3a was obtained and the photosynthetic index under salt–alkali treatments was evaluated. The transgenic line exhibited a series of negative regulation relative to the wild-type control. Quantitative real time polymerase chain reaction revealed that the physiological parameters, including soluble sugar, free proline, and chlorophyll contents; and photosynthetic rate decreased in the transgenic plants. Furthermore, GmMYB3a overexpression down-regulated a set of key genes associated with plant defense signal pathways. These finding suggest that GmMYB3a negatively affects the response of plants to salt stress.

ФОТОСИНТЕТИЧЕСКАЯ ДЕЯТЕЛЬНОСТЬ ПОСЕВОВ ДОННИКА ВТОРОГО ГОДА ЖИЗНИ

The article discusses the influence of late fodder miliary cover crops on the photosynthetic activity of second year plants of the sweet clover of life in the conditions of the South-Eastern part of the Volga-Vyatka zone. The determination of the dependence of the sweet clover productivity on various factors makes it difficult for a variety of reasons, connected with the photosynthetic activity of plants. But the productivity of yellow sweet clover crops significantly increases when optimizing the basic conditions necessary for growing plants, when all the photosynthetic activity of plants, which is the most complicated integration process, increases. In this study, in order to determine the sweet clover productivity, the optimal parameters of the most important photosynthetic parameters were determined in the first place, under which high plant productivity is formed. For example, the size of the leaf surface, the net productivity of photosynthesis and the coefficient of photosynthetically active radiation, which are the most optimal parameters of photosynthetic indices. The assimilating surface of the leaf surface of plants, per unit area of sowing, determines the absorption of photosynthetically active radiation by plants. Optimum leaf area, according to A.A. Nichiporovich (1970), L.G. Shashkarov (2006), for the sweet clover is the surface up to 40 thousand square meter, but when growing plants for harvesting, the area of leaves can be increased up to 70 thousand square meter per hectare, which, in turn, allows you to prepare a better feed. Studies have shown that for all years the maximum net productivity of photosynthesis was in yellow sweet clover plants in the variant when the plant was cultivated when sown without cover of late prosoidal cover crops (3.11 g / m2 per day), which allowed it to accumulate the greatest amount of dry matter (4.39 tons per hectare). All the studied late cover crops reduced this indicator of net photosynthetic productivity: in millet variants it was 2.66-2.76, with Sudan grass - 2.36-2.41 and with corn - 2.69-2.76 g / m2 per day. Decrease in the sowing norms of late forage cover crops from conventional values by 25% favorably affected the plants of sweet clover and improved their photosynthetic activity.