Cuttings of Populus cathayana Rehd, originating from three triploid and one diploid populations with the same parents but different gamete origins, were used to examine physiological responses to drought stress and rewatering by exposure to three progressive water regimes. Progressive drought stress significantly decreased the leaf relative water content (RWC), photosynthesis, and chlorophyll fluorescence parameters, and increased the relative electrolyte leakage, malondialdehyde (MDA), free proline (Pro), and antioxidant enzymes, such as superoxide dismutase, peroxidase, and catalase, in the four populations evaluated. However, compared to the diploid population, triploid populations showed lower relative electrolyte leakage and MDA, higher RWC and Pro content, and more efficient photosynthesis and antioxidant systems under the same water regime. Our data indicated that triploid populations possessed more efficient protective mechanisms than that of diploid population with gradually increasing drought stress. Moreover, some triploid genotypes were less tolerant to water stress than that of diploids due to large intrapopulation overlap., T. Liao, Y. Wang, C. P. Xu, Y. Li, X. Y. Kang., and Obsahuje bibliografii
Cotton (Gossypium hirsutum L.) yields are impacted by overall photosynthetic production. Factors that influence crop photosynthesis are the plants genetic makeup and the environmental conditions. This study investigated cultivar variation in photosynthesis in the field conditions under both ambient and higher temperature. Six diverse cotton cultivars were grown in the field at Stoneville, MS under both an ambient and a high temperature regime during the 2006-2008 growing seasons. Mid-season leaf net photosynthetic rates (PN) and dark-adapted chlorophyll fluorescence variable to maximal ratios (Fv/Fm) were determined on two leaves per plot. Temperature regimes did not have a significant effect on either PN or Fv/Fm. In 2006, however, there was a significant cultivar × temperature interaction for PN caused by PeeDee 3 having a lower PN under the high temperature regime. Other cultivars' PN were not affected by temperature. FM 800BR cultivar consistently had a higher PN across the years of the study. Despite demonstrating a higher leaf Fv/Fm, ST 5599BR exhibited a lower PN than the other cultivars. Although genetic variability was detected in photosynthesis and heat tolerance, the differences found were probably too small and inconsistent to be useful for a breeding program., W. T. Pettigrew., and Obsahuje bibliografii
Warming winter and atmospheric nitrogen (N) deposition are expected to have effects on net primary production (NPP) of Chinese fir (Cunninghamia lanceolata) plantation and implications for plantation carbon sequestration. The effects of nongrowing-season warming on plant morphological and physiological traits were investigated in a greenhouse experiment with two-year-old C. lanceolata seedlings. Elevated temperature (ET) during the nongrowing season significantly increased the net photosynthetic characteristics. The strongest effects occurred during warming period from 1 December 2014 to 1 February 2015 (W1). Moreover, the carbohydrate concentration was elevated due to the warming during W1, but it declined during four months of the warming (from 1 December 2014 to 1 April 2015, W2). The seedlings kept under N deposition (CN) showed a positive effect in all the above-mentioned parameters except δ13C. Significant interactions between ET and N deposition were observed in most parameters tested. At the end of the experiment (W2), the seedlings exposed to a combined ET and N deposition treatment exhibited the highest carbon contents. Our results showed that N deposition might ameliorate the negative effects of the winter warming on the carbon content., L. Yu, T. F. Dong, Y. B. Lu, M. Y. Song, B. L. Duan., and Obsahuje bibliografii
The influence of various concentrations of imazapic residues (0-800 μg kg-1) on the growth, chlorophyll content, and photosynthetic characteristics of maize seedlings was studied in a greenhouse pot experiment. Plant height, root length, shoot dry mass, root dry mass, and total dry mass of maize declined with the increase of imazapic residue concentrations. The root/shoot ratio initially decreased and then increased in presence of imazapic, which indicated that the effects of imazapic residues on plant height and root length might differ in maize seedlings. Lowered chlorophyll content and net photosynthetic rate were observed in leaves of maize seedlings in all treatments and indicated a dose-response relationship to imazapic concentrations. Intercellular carbon dioxide concentration, transpiration rate, and stomatal conductance also declined to varying extents, but the chlorophyll a/b ratio increased gradually together with the increase of imazapic residue concentrations. Generally, the maize seedlings were negatively affected by the imazapic residues in soil. Response of root length and biomass to imazapic residues could be the important index for maize variety selection., W. C. Su, L. L. Sun, R. H. Wu, Y. H. Ma, H. L. Wang, H. L. Xu, Z. L. Yan, C. T. Lu., and Obsahuje bibliografii
Calligonum caput-medusae is known to grow well when irrigated with water containing NaCl. The aim of this study was to investigate ecophysiological responses of C. caput-medusae to different NaCl concentrations. In our study, we examined the effect of 0, 50, 100, 200, and 400 mM NaCl. Our results demonstrated that maximum seedling growth occurred at 50 mM NaCl. Photosynthetic parameters, such as the photosynthetic pigment content and gas exchange parameters, correlated with growth response. High salinity (≥ 100 mM NaCl) resulted in a significant reduction of the plant growth. Similarly, marked declines in the pigment content, maximal efficiency of PSII photochemistry, net photosynthetic rate, transpiration rate, and stomatal conductance were also detected. However, intercellular CO2 concentration showed a biphasic response, decreasing with water containing less than 200 mM NaCl and increasing with NaCl concentration up to 400 mM. Water-use efficiency and intrinsic water-use efficiency exhibited the opposite response. The reduction of photosynthesis at the high NaCl concentration could be caused by nonstomatal factors. High salinity led also to a decrease in the relative water content and water potential. Correspondingly, an accumulation of soluble sugars and proline was also observed. Na+ and
Cl- concentrations increased in all tissues and K+ concentrations were maintained high during exposure to NaCl compared with the control. High salinity caused oxidative stress, which was evidenced by high malondialdehyde and hydrogen peroxide contents. In order to cope with oxidative stress, the activity of antioxidative enzymes increased to maximum after 50 mM NaCl treatment. The data reported in this study indicate that C. caput-medusae can be utilized in mild salinity-prone environments., Y. Lu, J.-Q. Lei, F.-J. Zeng, B. Zhang, G.-J. Liu, B. Liu, X.-Y. Li., and Obsahuje bibliografii
In order to evaluate effect of weedy rice on the photosynthesis and grain filling of cultivated rice, cultivated rice ‘Nanjing 44‘ was planted in the field under different densities of weedy rice ‘JS-Y1‘ for two years. The results showed that net photosynthetic rate (PN), net assimilation rate, grain filling rate, and the grain yield of cultivated rice all decreased with increasing weedy rice density. Furthermore, yield component analysis revealed that increasing weedy rice density had the most significant effect on the percentage of filled grains and the number of rice panicles. The correlation analyses indicated that the yield of cultivated rice was highly correlated with the net photosynthetic rate and the net assimilation rate. Our results illustrated that high density of weedy rice might cause yield losses in cultivated rice by inhibition of photosynthesis and grain filling., X. M. Xu, G. Li, Y. Su, X. L. Wang., and Obsahuje bibliografii
Effects of root treatment with 5-aminolevulinic acid (ALA) on leaf photosynthesis in strawberry (Fragaria ananassa Duch.) plants were investigated by rapid chlorophyll fluorescence and modulated 820 nm reflection using 3-(3,4-dichlorophenyl)-1,1-dimethyl urea (DCMU) and methyl viologen (MV). Our results showed that ALA treatments increased the net photosynthetic rate and decreased the intercelluar CO2 concentration in strawberry leaves. Under DCMU treatment, trapping energy for QA reduction per PSII reaction center increased greatly, indicating DCMU inhibited electron transfer from QA−. The maximum photochemical efficiency of PSII (Fv/Fm) decreased under the DCMU treatment, while a higher Fv/Fm remained in the ALA-pretreated plants. Not only the parameters related to a photochemical phase, but also that one related to a heat phase remained lower after the ALA pretreatment, compared to the sole DCMU treatment. The MV treatment decreased PSI photochemical capacity. The results of modulated 820 nm reflection analysis showed that DCMU and MV treatments had low
re-reduction of P700 and plastocyanin (PSI). However, the strawberry leaf discs pretreated with ALA exhibited high re-reduction of PSI under DCMU and MV treatments. The results of this study suggest that the improvement of photosynthesis by ALA in strawberry was not only related to PSII, but also to PSI and electron transfer chain., Y. P. Sun, J. Liu, R. X. Cao, Y. J. Huang, A. M. Hall, C. B. Guo, L. J. Wang., and Obsahuje bibliografii
Our study investigated the physiological and biochemical basis for the effects of exogenous phenolic acids on the function of the photosynthetic apparatus and photosynthetic electron transport rate in strawberry seedlings. Potted seedlings of the strawberry (Fragaria × ananassa Duch.) were used. Syringic acid inhibited net photosynthetic rate and water-use efficiency decreased. Additionally, primary quinone electron acceptor of the PSII reaction centre, the PSII reaction centre and the oxygen evolving complex were also impaired. Both the maximum quantum yield of the PSII primary photochemistry and the performance index on absorption basis were depressed, resulting in reduced function of the photosynthetic electron transport chain. Otherwise, low phthalic acid concentrations enhanced photosynthetic capacity, while high concentrations showed opposite effects. Syringic acid exhibited a higher toxic effect than that of phthalic acid which was more evident at higher concentrations., X. F. Lu, H. Zhang, S. S. Lyu, G. D. Du, X. Q. Wang, C. H. Wu, D. G. Lyu., and Obsahuje bibliografii
Broomcorn millet (Panicum miliaceum L.) is one of the important C4 crops in the semiarid regions of northern China. It is a close relative of biofuel crop switchgrass. Yet, there is no information on how these crops might respond to a climate change in China. In order to gain insight into such a response, we studied the effect of elevated CO2 concentration (EC) on broomcorn millet. The changes in leaf photosynthesis, chlorophyll fluorescence, morphological parameters, biomass and yield in response to EC [i.e., + 200 µmol(CO2) mol-1] over two years were determined at the open-top chamber (OTC) experimental facility in north China. EC increased net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, transpiration rate, instantaneous transpiration efficiency, effective quantum yield of PSII photochemistry, and photochemical quenching coefficient of fully expanded flag leaves. Maximal quantum yield of PSII photochemistry declined under EC in 2013, but was not affected in 2014. EC significantly decreased intrinsic efficiency of PSII in 2013, but increased in 2014. Leaf nonphotochemical quenching decreased under EC both in 2013 and 2014. EC significantly enhanced the aboveground biomass and yield by average of 31.4 and 25.5% in both years, respectively. The increased yield of broomcorn millet under EC occurred due to the enhanced number of grains per plant. We concluded that photosynthesis of broomcorn millets was improved through increased stomatal conductance in leaves under EC, which led to an increase in height, stem diameter, aboveground biomass, and yield. This study extends our understanding of the response of this ancient C4 crop to elevated CO2 concentration., X. Y. Hao, P. Li, H. Y. Li, Y. Z. Zong, B. Zhang, J. Z. Zhao, Y. H. Han., and Obsahuje bibliografii
Our experiment was carried out in order to explore effects of plant growth regulators (PGR; thidiazuron, paclobutrazol, and ascorbic acid) on physiological traits of wheat genotypes under water surplus and deficit conditions. Study revealed that relative water content, membrane stability index, chlorophyll content, photosynthetic rate (PN), and maximal quantum yield of PSII improved with PGRs application across the genotypes both under irrigation and water stress. The response of HD 2733 genotype was more positive toward PGRs treatment as compared to other genotypes under water stress. Higher PN and chlorophyll contents were observed in HD 2987 followed by C 306 genotype under water-stress conditions. Moreover, Rubisco small subunit (SSU) expression was lower in wheat genotypes under water stress as compared to irrigated conditions. Application of PGRs led to upregulation of SSU under water stress, while no significant change was found in Rubisco level and activity under irrigated condition in dependence on PGRs treatments. Yield-related traits showed also significant reduction under water-stress conditions, while application of PGRs enhanced the yield and its components. Results indicated that the PGRs exhibited a positive interaction and synergetic effect on water stressed wheat plants in terms of photosynthetic machinery and yield., S. K. Dwivedi, A. Arora, V. P. Singh, G. P. Singh., and Obsahuje bibliografii