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
Growth and physiological responses of cotton (Gossypium hirsutum L.) cultivars with different phosphorus (P) efficiencies under variable P environment are poorly known. Therefore, this study explored effects of normal P [P+, 70 kg(P2O5) ha-1] and without P (P-, 0 kg ha-1) on yield, growth, and physiology of different P-efficient cultivars [low-efficient Xinluzao 13 (L1) and Xinluzao 26 (L2); medium-efficient Xinluzao 10 (M1) and Xinluzao 24 (M2);
high-efficient Zhongmiansuo 42 (H1) and Xinluzao19 (H2)]. Cotton growth and yield was higher in H1 and H2 cultivars under P+ compare to P-. Leaf photosynthesis, intercellular CO2 concentration, stomatal conductance, and net assimilation rate increased under P+ and in high-efficient cultivars. Greater Rubisco activity and higher soluble sugar content further promoted P uptake and utilization efficiency which resulted in a higher yield under normal P+ than that at P- treatment. High-P-efficient cultivars have the potential to increase the yield by improving cotton growth and physiological attributes under P+., J. Wang, Y. Chen, P. Wang, Y. S. Li, G. Wang, P. Liu, A. Khan., and Obsahuje bibliografii
Zinc is a critical mineral nutrient that protects plant cells from salt-induced cell damage. We tested whether the application of Zn at various concentrations [0, 5, 10, or 20 mg kg-1(soil)] would protect almond (Prunus amygdalus) seedlings subjected to salt stress (0, 30, 60, or 90 mM NaCl). All concentrations of Zn, particularly the application of 10 and 20 mg kg-1, increased the net photosynthetic rate, stomatal conductance, the maximal efficiency of PSII photochemistry, and a proline content in almond seedlings grown under salt stress; 20 mg(Zn) kg-1 was the most effective concentration. The activity of superoxide dismutase showed a significant increase under salinity stress and Zn application. The catalase activity decreased in the salt-treated seedlings, but recovered after the Zn treatment. Our results proved the positive effects of Zn on antioxidant enzyme activity scavenging the reactive oxygen species produced under salt stress., A. Amiri, B. Baninasab, C. Ghobadi, A. H. Khoshgoftarmanesh., and Obsahuje seznam literatury