Excessive cadmium (Cd) content in soil leads to a number of phytotoxic effects and challenges agricultural production. Aim of this study was to investigate different responses of two maize inbreds and their hybrid to an elevated Cd content in soil by measuring photosynthetic and biochemical activity and to identify a Cd tolerance mechanism. Antioxidant statusrelated parameters varied significantly between inbreds and treatments. Dry mass increased in both inbreds, but remained unchanged in hybrid. After the Cd treatment, parameters of chlorophyll a fluorescence varied between inbreds and hybrid performance was similar to inbred B84. We concluded that inbred B84 is Cd-sensitive compared to Os6-2, which did not appear to be negatively affected by Cd treatment at this growth stage studied. We suspect that due to a dilution effect in the hybrid, there was no or very weak Cd stress detected by biochemical parameters, although stress was detected by chlorophyll a fluorescence., M. Franić, V. Galić, M. Mazur, D. Šimić., and Obsahuje bibliografii
Tobacco (Nicotiana tabacum L.) has been transformed to accumulate different compatible solutes (proline, fructans, or glycine betaine) in order to improve its tolerance to abiotic stress. Photosynthetic activity of wild Type (wt) and transformed tobacco plants before and after freezing stress was studied by measuring chlorophyll (Chl) fluorescence. The JIP test of Chl fluorescence induction was used to analyze in details the functional activity of photosystem 2. No significant differences were found among wild Type and transgenic plants after 12 h of freezing. Both plant Types maintained the same values of the measured parameters [FV/FM, PI(CSM), ABS/RC, TR0/RC, ET/RC] after recovery of stress. The studied Chl fluorescence parameters decreased only for the wild Type plants, stressed for 24 h at -2 °C. The strong inhibition of photosynthetic reactions in the wt plant after 24 h of freezing could not be restored. The evaluated parameters of transgenic plants did not change significantly after 24 h at -2 °C and successfully survived freezing stress. and D. Parvanova ... [et al.].
Watermelon [Citrullus lanatus (Thunb.) Mansfeld] is a photophilic plant, whose net photosynthetic rate was significantly decreased when seedlings were grown under low light condition. However, treatment with 100 mg kg-1 5-aminolevulinic acid (ALA) could significantly restore the photosynthetic ability under the environmental stress. The parameters of leaf gas exchange, chlorophyll modulated fluorescence and fast induction fluorescence of the ALA-treated plants were higher than that of the control. Additionally, ALA treatment increased the activities of antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POD) and ascorbate peroxidase (APX). Nevertheless, the treatment of diethyldithiocarbamate (DDC), an inhibitor of SOD activity, dramatically depressed photosynthesis of watermelon leaves, while ALA could reverse the inhibition of DDC. Therefore, it can be deduced that ALA promotion on photosynthesis of watermelon leaves under low light stress is attributed to its promotion on antioxidant enzyme activities, and the increased activities of the enzymes, which are mainly located near the reaction centers of PSI, can scavenge superoxide anions, leading to an increase of apparent electron transport rate and an alleviation of photosynthetic photoinhibition under the stressed environment. and Y.-P. Sun, Z.-P. Zhang, L.-J. Wang.
The study examined photosynthetic efficiency of two barley landraces (cvs. Arabi Abiad and Arabi Aswad) through a prompt fluorescence technique under influence of 14 different abiotic stress factors. The difference in the behavior of photosynthetic parameters under the same stress factor in-between cv. Arabi Abiad and cv. Arabi Aswad indicated different mechanisms of tolerance and strategies for the conversion of light energy into chemical energy for both the landraces. This study confirmed the suitability of some chlorophyll fluorescence parameters as reliable biomarkers for screening the plants at the level of photosynthetic apparatus., H. M. Kalaji, A. Rastogi, M. Živčák, M. Brestic, A. Daszkowska-Golec, K. Sitko, K. Y. Alsharafa, R. Lotfi, P. Stypiński, I. A. Samborska, M. D. Cetner., and Obsahuje bibliografii
WN6 (a stay-green wheat cultivar) and JM20 (control) were used to evaluate the effects of exogenous cytokinin on photosynthetic capacity and antioxidant enzymes activities in flag leaves. Results showed that WN6 reached the higher grain mass, which was mainly due to the higher photosynthetic rate resulting from the higher maximal quantum yield of PSII photochemistry (ΦPSII) and probability that a trapped exaction transfers an electron into the electron transport chain beyond QA (Ψo), and lower relative variable fluorescence intensity at the J-step (Vj). Exogenous 6-benzylaminopurine (6-BA) enhanced antioxidant enzymes activities and decreased malondialdehyde (MDA) content. Enhanced Ψo and electron transport rate (ETR), and decreased Vj contributed to improved photosynthetic rate in the 6-BA treatment. In addition, exogenous 6-BA significantly increased endogenous zeatin (Zt) content, which was significantly and positively correlated with the antioxidant enzyme activity and ΦPSII, implying that higher Zt content was responsible for the improved antioxidant status and photosynthetic performance., D. Q. Yang, Y. L. Luo, W. H. Dong, Y. P. Yin, Y. Li, Z. L. Wang., and Obsahuje bibliografii
The objective of this study was to evaluate the significance of blue light (B) in the growth and photosynthetic capacity of cucumber. Gas exchange, chlorophyll (Chl) fluorescence kinetics, chloroplast ultrastructure, and leaf growth were investigated to explore the influence of three different light qualities of light emitting diodes (LEDs) on plant morphogenesis and the development of photosynthetic apparatus in cucumber (Cucumis sativus) leaves from emergence to full expansion under weak light [50 μmol(photon) m-2 s-1]. We found that B could significantly increase the leaf area (LA), shoot elongation, Chl a/b, net photosynthetic rate, and stomatal conductance (g s). In addition, the comparisons of maximal quantum yield of PSII photochemistry and the photosynthetic performance index between B-, W (white light)-, and R (red light)-grown leaves suggested that B was essential for the development of photosynthetic apparatus under weak light. B-grown leaves had the lowest Chl content under weak light, however, they had well-developed chloroplasts with the highest degree of stacked lamellae and the lowest starch accumulation. This could explain to a considerable extent the highest net photosynthetic rate per Chl unit. The results demonstrated that B optimized photosynthetic performance by improving the photosynthetic rate, increasing LA, and prolonging active photosynthesis duration under low irradiance. Therefore B is necessary to ensure healthy development of chloroplasts and highly efficient photosynthetic functions in cucumbers under a weak light environment. More importantly, our study also provided theoretical and technical support for the development of light environmental control technology., X. Y. Wang, X. M. Xu, J. Cui., and Obsahuje bibliografii