To understand the physiology of rice under seawater salinity, potted rice plants were irrigated with different concentrations of Japan seawater (electrical conductivity 0.9, 5.7, 11.5, or 21.5 mS cm-1) from 10 d after transplanting (DAT) to 35 DAT, and from 75 to 100 DAT. Seawater salinity decreased the net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, transpiration rate, leaf water and osmotic potentials, and relative water content, and increased leaf temperature. The contents of chlorophylls, carotenoids, and total sugars significantly decreased in the leaves but content of non-reducing sugars decreased only slightly. With increasing salinity the Na+ concentration increased, while Ca2+, Mn2+, and K+ concentrations decreased. Salinity decreased the contents of sugars and proteins, dry mass, and rate of dry mater accumulation in developing grains. and N. Sultana, T. Ikeda, M. A. Kashem.
Pearl millet (Pennisetum glaucum L. cv. HHB-67) seeds were pre-soaked in sulphydryl compounds (dithiothreitol, thioglycollic acid, thiourea, and cysteine). In plants at 59 and 67 d after sowing (DAS), activities of photosystem (PS) 2 (ferricyanide site) and PS1, both chloroplastic and total superoxide dismutase, glutathione reductase, and glutathione-S-transferase increased after all sulphydryl pre-treatments at both stages of plant development. Also dry matter of plant parts sampled at 55 DAS was higher after thiol-treatments in comparison with control. and N. K. Ramaswamy ... [et al.].
In order to study the mechanisms of Se-mediated growth improvement as related to carbon (C) and nitrogen (N) metabolism, wheat plants were cultivated hydroponically with adequate (4 mM, Na) or low (1 mM, Nd) N supply and treated with 10 and 50 μM Na2SeO4 for six weeks. The Se supplementation enhanced plant biomass; it was significant for shoots of Na plants at 50 μM Se. Chlorophyll fluorescence parameters were significantly lowered under Nd conditions but restored completely by Se addition reaching values of those in Na plants. Net CO2 assimilation rate (PN) decreased only slightly by limited N availability, but it enhanced significantly in both Nd and Na plants equally by 10 and 50 μM Se. Effect of Se on PN in the Na plants occurred mainly due to the stomata opening, while it was related to both stomatal and nonstomatal mechanisms in the Nd plants. The Se treatment resulted in enhancement of nitrate reductase (NR) activity in both Na and Nd plants with an optimal response at 10 μM Se. Negative correlations between nitrate concentration and NR activity indicated a partial nitrate depletion in the roots following by elevated NR activity in Nd plants. In contrast, nitrite concentrations were higher in the Se treated plants. Higher amino acids and protein concentrations in the Se-treated plants might be an indication of a general upregulation of N metabolism. However, in Na plants, the stimulation of N metabolism was not observed at 50 μM Se which could not be attributed to lesser availability of C skeletons because of maintaning higher CO2 fixation under these conditions. It implies the function of some regulatory mechanisms that are responsible for coordination of C and N metabolism in whole plant., R. Hajiboland, N. Sadeghzade., and Obsahuje bibliografii
Freezing of thylakoid membranes in the presence of 0.1 M NaCl and increasing concentrations of serine changed the photochemical actívity of photosystem (PS) 2 with beginning of freezing, while the PSI mediated electron transport was altered after a 24 h storage at -20 °C.
The objective of this study was to investigate a response to low-light environments in hybrids and commercial cultivars of Boehmeria nivea L. Two hybrids (Chuanzhu 11 and Chuanzhu 8) and two commercial cultivars (Chuanzhu 12 and Chuanzhu 6) of ramie were subjected to a shade treatment for 6, 12, and 18 days. The shade treatment led to a significant decrease in some plant traits and fiber yield in four ramie cultivars, whereas their leaf area and plant height increased. In addition, net photosynthesis and stomatal conductance significantly declined in response to shade, while transpiration rate and intercellular CO2 did not significantly change. Moreover, chlorophyll (Chl) and carotenoid (Car) concentration, Chl/Car, and Chl (a+b) per leaf dry mass significantly increased in the response to shade, while the Chl a/b ratio decreased. Furthermore, Chuanzhu 6 and Chuanzhu 11 were more tolerant to shade than Chuanzhu 12 and Chuanzhu 8, thus, they could be potentially used for management practices and breeding programs., C.-J. Huang, G. Wei, Y.-C. Jie, J.-J. Xu, S. A. Anjum, M. Tanveer., and Seznam literatury
Little is known regarding to impact of simulated shading conditions on cotton yield and fiber quality at different fruiting positions. In this 2-year study, our field experiments investigated the effects of shading percentage on the cotton yield, fiber properties, photosynthesis, and carbohydrate concentrations in boll's subtending leaves during various growing stages at different fruiting positions (FP). Net photosynthetic rate and effective quantum yield of PSII photochemistry decreased in response to shading on both FP1 and FP3 of the 7th sympodial branches, respectively. Shading also reduced sucrose and starch contents of leaves at each fruiting position. Shading decreased the number and mass of cotton bolls, the fiber strength and micronaire, while the fiber length increased at both fruiting positions. Our results suggested that shading resulted in the reduction of the cotton yield and fiber quality, which are mainly associated with the changes in boll number and alteration of photosynthesis and carbohydrate concentrations during the boll development., B. L. Chen, H. K. Yang, Y. N. Ma, J. R. Liu, F. J. Lv, J. Chen, Y. L. Meng, Y. H. Wang, Z. G. Zhou., and Obsahuje bibliografii
Alkaline stress is important abiotic stress that restricts the growth and physiological activity of sorghum (Sorghum bicolor L. Moench). We aimed to investigate the effects of alkaline stress on alkali-tolerant SX44B and alkali-sensitive 262B sorghum inbred lines. The results showed that alkaline stress decreased the content of chlorophyll, activity of photosystem II, net photosynthetic rate, and destroyed chloroplast morphology. These changes were less pronounced in SX44B, possibly owing to its higher antioxidant enzyme activity and nonphotochemical quenching. Alkaline stress decreased water content, transpiration rate, and stomatal conductance while increasing the leaf temperature, with the effect being more pronounced in 262B. A significant correlation was observed between leaf-air temperature difference (ΔT) and relative water content and gas-exchange parameters, especially in 262B. Therefore, ΔT is an effective indicator for monitoring changes in sorghum leaves under alkaline stress and evaluating the alkali tolerance of different sorghum germplasm.
In greenhouse experiments the efFect of simulated acid rain (mist of H2SO4) treatment on i'*C02 fixation, ribulose-l,5-bisphosphate carboxylase (RuBPC), nitráte reductase (NR) and nitrite reductase (NiR) activities in Vigna sinensis L. and Phaseolus mungo L. was investigated at different pH. Seedlings exposed to acidic mists of pH 5.6, 4.0 and 2.0 for 5 d showed significant reduction in *“*€02 fixation, RuBPC, NiR and especially NR activities. Sodium dodecylsulphate polyacrylamide gel electrophoresis (SDS-PAGE) of crude leaf extracts of RuBPC indicated a significant loss of 55 and 15 kDa polypeptides at pH 2.0 in both the crop plants. The reduction in the RuBPC activity in seedlings grown under acidic mists correlated well with the CO2 fixation. NR activity was affected more than the NiR activity.
An experiment was conducted to study the effect of NaCl (electric conductivity of 0, 4, 8, 12, and 16 dS m-1) on growth, gas exchange parameters, water status, membrane injury, chlorophyll stability index and oxidative defense mechanisms in two cultivars (Gola and Umran) of Indian jujube (Ziziphus mauritiana). Results showed that the dry mass and leaf area reduced linearly with increasing levels of salinity. Net photosynthetic rate (PN), transpiration (E), and stomatal conductance (gs) were comparatively lower in Umran which further declined with salinity. Leaf relative water content, chlorophyll (Chl) stability and membrane stability also decreased significantly under salt stress, with higher magnitude in Umran. Superoxide dismutase (SOD), peroxidase (POX) and catalase (CAT) activities were higher in Gola whereas hydrogen peroxide (H2O2) accumulation and lipid peroxidation (MDA content) were higher in control as well as salttreated plants of Umran. The Na+ content was higher in the roots of Gola and in the leaves of Umran, resulting in high K+/Na+ ratio in Gola leaves. Thus it is suggested that salt tolerance mechanism is more efficiently operative in cultivar Gola owing to better management of growth, physiological attributes, antioxidative defense mechanism, and restricted translocation of Na+ from root to leaves along with larger accumulation of K+ in its leaves., R. Agrawal ... [et al.]., and Obsahuje bibliografii
In our study, one-month-old Melissa officinalis plants were subjected to Fe-deficiency treatments, such as 10 µM Fe (as direct iron deficiency, DD), and 30 µM Fe + 10 mM NaHCO3 + 0.5 g l-1 CaCO3 (as indirect iron deficiency, ID), and 30 µM Fe (as control) for 14 d. Both Fe-deficiency types reduced plant growth, photosynthetic pigment contents, an active Fe content in roots and leaves, root Fe(III)-reducing capacity, Fe-use efficiency, maximal quantum yield of PSII photochemistry, a ratio of variable to basic fluorescence, and activities of antioxidant enzymes, while they increased lipid peroxidation and a H2O2 content in leaves. These effects were more pronounced in plants exposed to ID with bicarbonate than those of DD plants. We showed that sodium nitroprusside (SNP), as NO donor, could ameliorate the adverse effects of bicarbonate on above traits. The methylene blue, as NO blocker, reversed the protective effects conferred by SNP in the ID-treated plants as well as DD plants. These findings suggests that NO protects photosynthesis and growth of IDtreated plants as well as DD plants by contribution in availability and/or delivery of metabolically active iron or by changing activities of reactive oxygen species-scavenging enzymes., R. Amooaghaie, Sh. Roohollahi., and Obsahuje bibliografii