Aqueous solutions of salicylic acid (SA) were applied to the foliage of 30-d-old plants of mustard (Brassica juncea Czern & Coss cv. Varuna). The plants sprayed with the lowest used concentration (10-5 M) of SA were healthier than those sprayed with water only or with higher concentrations of SA (10-4 or 10-3 M). 60-d-old plants possessed 8.4, 9.8, 9.3, 13.0 and 18.5 % larger dry mass, net photosynthetic rate, carboxylation efficiency, and activities of nitrate reductase and carbonic anhydrase over the control, respectively. Moreover, the number of pods and the seed yield increased by 13.7 and 8.4 % over the control. and Q. Fariduddin, S. Hayat, A. Ahmad.
Salicylic acid (SA) and nitric oxide (NO) form a new group of plant growth substances that cooperatively interact to promote plant growth and productivity. Water deficit (WD) stress is a major limiting factor for photosynthesis, which in turn limits crop yield. However, the mechanism of SA and NO in stimulating photosynthesis has not yet been elucidated. Therefore, in this study, we investigated the SA- and NO-mediated photosynthetic adaptability of maize seedlings to WD in terms of photosynthetic parameters, activities and mRNA levels of CO2 assimilation enzymes. Our results showed that SA alleviated the WD-induced reduction of photosynthetic performance. The activities of Rubisco and Rubisco activase enzymes increased significantly due to SA pretreatment. Moreover, higher transcription rates of Rbc L, ZmRCAα and ZmRCAβ mRNA further confirmed the effects of SA on CO2 assimilation. WD or SA-induced decreases or increases of CO2 assimilation ability were further decreased after c-PTIO addition., R. X. Shao, L. F. Xin, J. M. Guo, H. F. Zheng, J. Mao, X.P. Han, L. Jia, S. J. Jia, C. G. Du, R. Song, Q. H. Yang, R. W. Elmore., and Obsahuje bibliografii
The effects of drought oř salinity (NaCl) stress in combination wifh high irradiance (HI) were studied under the laboratory conditions, using young plants of a drought- resistant cultivar of Sorghum bicolor in order to understand leaf observed effects at the chloroplast level. Water potential and net photosynthetic rate (P^j) in leaves were analyzed in parallel with photosynthetic electron transport, electron spin resonance and chlorophyll-protein (CP) composition in chloroplasts isolated from these stressed leaves. The H1 slightly increased and electron transport activities of the irrigated plants, whereas drougbt and salinity stresses (leaf water potential lower than -1 MPa) decreased these activities. Under the combined effects of drought or salinity stress (200 mM NaCl) with HI the leaf Pjj was severely inhibited, as were photosystem (PS) 2 chloroplast electron transport activities (but not PS 1 activity). NaCl concentrations lower than 100 mM stimulated the electron transport activities in non-photoinhibited plants. A degradation of the PS 2 CFs and a decrease of ESR signál n were seen in the drought and salinity stressed plants afler HI.
The role of the antioxidant defense system in salt tolerance of Aeluropus littoralis has not been yet reported; therefore in the present study, the changes of catalase (CAT) activity in this halophyte plant was investigated and CAT gene was isolated. The leaves of treated and control plants were harvested at various times, starting 1 day prior to initiating treatment, then periodically at 72-h intervals for 21 days. The data collected showed that CAT activity increased significantly with time in plants treated with 200, 400, and 600 mM NaCl when compared with the control plants. Maximum enzyme activity was observed between the 6th and 12th day at all NaCl concentrations. CAT gene was isolated and cloned via pTZ57R/T cloning vector in Escherichia coli. CAT gene encoded 494 amino acids and had also high homology of 90, 87, 86, and 86% with CAT genes from Zea mays, Oryza sativa, Triticum aestivum, and Hordeum vulgare, respectively. and M. Modarresi, G. A. Nematzadeh, F. Moradian.
Sixty seven-days-old plants of Ammi majus L. were subjected for 46 d to sand culture at varying concentrations of NaCl, i.e. 0 (control), 40, 80, 120, and 160 mM. Increasing salt concentrations caused a significant reduction in fresh and dry masses of both shoots and roots as well as seed yield. However, the adverse effect of salt was more pronounced on seed yield than biomass production at the vegetative stage. Calculated 50 % reduction in shoot dry mass occurred at 156 mM (ca.15.6 mS cm-1), whereas that in seed yield was at 104 mM (ca.10.4 mS cm-1). As in most glycophytes, Na+ and Cl- in both shoots and roots increased, whereas K+ and Ca2+ decreased consistently with the successive increase in salt level of the growth medium. Plants of A. majusmaintained markedly higher K+/Na+ ratios in the shoots than those in the roots, and the ratio remained more than 1 even at the highest external salt level (160 mM). Net photosynthetic (PN) and transpiration (E) rates remained unaffected at increasing NaCl, and thus these attributes had a negative association with salt tolerance of A. majus. Proline content in the shoots increased markedly at the higher concentrations of salt. Essential oil content in the seed decreased consistently with increase in external salt level. Overall, A. majusis a moderately salt tolerant crop whose response to salinity is associated with maintenance of high shoot K+/Na+ ratio and accumulation of proline in shoots, but PN had a negative association with the salt tolerance of this crop. and M. Ashraf ... [et al.].
The oligomeric state of photosystem 2 (PS2) complex in soybean leaves treated with saturating irradiance was studied by non-denaturing polyacrylamide gel electrophoresis (PAGE) and gel filtration chromatography. PS2 dimers resolved by non-denaturing PAGE accounted for about 75 % of total PS2 complex and there was no significant difference in the ratio of PS2 dimer to monomer between samples from saturating irradiance-treated and fully dark-adapted leaves. Furthermore, BBY particles were resolved into four chlorophyll-enriched fractions by gel filtration chromatography. From their molecular masses and protein components, these fractions were deduced to be PS2 dimer, PS2 monomer, oligomeric light-harvesting complex 2 (LHC2), and monomeric LHC2. Also, no change in the proportion of PS2 dimer in total PS2 was observed in the granal region of thylakoid membranes from soybean leaves after saturating irradiation. Hence the dimer is the predominant natural form of PS2 in vivo and no monomerisation of PS2 dimer occurs during saturating irradiance-induced photoinhibition in soybean leaves. and Shi-Qing Cai ... [et al.].