No abstract

Water deficit is a key factor influencing the yield and quality of crops. In the present study, the photosynthetic responses by means of chlorophyll fluorescence of chloroplasts, thylakoid membrane proteins, and antioxidant components were analyzed in wheat (Triticum durum Desf.) plants differing in their tolerance to drought. Two durum winter wheat varieties, Barakatli 95 (drought tolerant) and Garagylchyg 2 (drought sensitive) were grown under field well-watered and drought conditions. It was found that contents of the PS I core (CPI) with Mr of 123 kD and apoprotein P700 with Mr of 63 kD were relatively higher in Barakatli 95 variety under drought stress compared with the control plants. Synthesis of α- and β-subunits of CF ATP-synthase complex with Mr of 55 and 53.5 kD also slightly increased in the tolerant Barakatli 95 and decreased in the drought sensitive variety Garagylchyg 2. A decrease in the intensity of 30 kD band and a significant increase were found in the content of the 25-16 kD region in Garagylchyg 2 variety. The synthesis of 60 kD and content of low molecular mass polypeptides (21.5 and 12 kD) were increased in the tolerant genotype Barakatli 95. The intensity of peaks at 687, 695, and 742 nm considerably increases in the fluorescence spectra (77 K) of chloroplasts isolated from the sensitive variety Garagylchyg 2, and there is a stimulation of the ratio of fluorescence band intensity F687/F740. At the same time, higher level of glycine betaine was found in the drought tolerant variety compared with the control one throughout the different periods of growth.

The dynamics of the activity of catalase, ascorbate peroxidase, guaiacol peroxidase, and benzidine peroxidase, as well as the level of hydrogen peroxide in the vegetative organs of durum wheat (Triticum durum Desf.) cultivars was studied under long-term soil drought conditions. It was established that hydrogen peroxide generation occurred at early stages of stress in the tolerant variety Barakatli-95, whereas in the susceptible variety Garagylchyg-2 its significant amounts were accumulated only at later stages. Garagylchyg-2 shows a larger reduction of photochemical activity of PS II in both genotypes at all stages of ontogenesis under drought stress than Barakatli-95. The highest activity of catalase which plays a leading role in the neutralization of hydrogen peroxide was observed in the leaves and roots of the drought-tolerant variety Barakatli-95. Despite the fact that the protection system also includes peroxidases, the activity of these enzymes even after synthesis of their new portions is substantially lower compared with catalase. Native PAGE electrophoresis revealed the presence of one isoform of CAT, seven isoforms of APX, three isoforms of GPO, and three isoforms of BPO in the leaves, and also three isoforms of CAT, four isoforms of APX, two isoforms of GPO, and six isoforms of BPO in the roots of wheat. One isoform of CAT was found in the roots when water supply was normal and three isoforms were observed under drought conditions. Stress associated with long-term soil drought in the roots of wheat has led to an increase in the heterogeneity due to the formation of two new sedentary forms of catalase: CAT2 and CAT3.

The ascorbate-glutathione (AsA-GSH) cycle is a major pathway of H2O2 scavenging in plants. The effect of diurnal variations in hydrogen peroxide (H2O2) content, the intensity of lipid peroxidation (malondialdehyde, MDA), photosynthesis, antioxidants and antioxidative enzyme activities involved in AsA-GSH metabolism has been studied comparatively in leaves of durum (Triticum durum Desf.) and bread (Triticum aestivum L.) wheat genotypes exposed to soil drought. Drought stress caused an increase in the content of H2O2, MDA, alterations in the activities of AsA-GSH cycle enzymes and quantitative changes in AsA and GSH content during the day. PSII efficiency was significantly lower in the control and drought exposed leaves at the highest temperature in the afternoon. The ascorbate peroxidase activity was found to increase and ascorbic acid amount decreased with increasing temperature during the day. Further, the glutathione amount and glutathione reductase activity increased at the expense of the regeneration of the oxidised form of glutathione. Our results revealed that wheat can tolerate drought stress by enhancing the antioxidant enzyme activities and alteration of the concentration of ascorbate and glutathione.

Land plants shorten their vegetation period during water deficiency. Under water stress, wheat plants undergo several changes at the morphophysiological level. We tried to elucidate the role of the morphophysiological parameters and the photosynthetic machinery in response to drought followed by rewatering. Therefore, some morphophysiological traits of two bread wheat genotypes (drought-tolerant Gobustan, drought-sensitive Tale 38) were studied. The H2O2 content increased under drought in both genotypes but recovered in the Gobustan genotype after rewatering. The isozymes of peroxidase manifested dynamic changes under drought. The electron transport rate and the maximum photochemical quantum efficiency of PSII showed similar responses to drought with subsequent rewatering in both genotypes. However, the amount of the photosynthetic pigments changed drastically resulting in structural changes of thylakoid membranes. In Gobustan, the thylakoid membrane structure almost completely recovered after rewatering. Thus, the drought-tolerant genotype shows a more dynamic response of photosynthetic machinery and antioxidant capacity.

No abstract

No abstract

Tomato samples were collected from the field of Absheron peninsula in Azerbaijan in order to evaluate the incidence of main Tobamoviruses. According to results of serological and molecular tests, Tomato mosaic virus (ToMV), Tobacco mosaic virus (TMV), and Pepper mild mottle virus (PMMoV) were detected as single and mixed infections (TMV + PMMoV; ToMV + PMMoV) in various tomato samples. It was found that Tobamovirus infection caused an increase in the content of malondialdehyde, alterations in the activities of peroxidase enzymes and quantitative and qualitative changes in their molecular isoforms. A comparison of thylakoid membrane polypeptides from virus-infected leaves indicated a decrease in the content of the thylakoid membrane polypeptides with molecular masses of 123, 55, 47, 33, 28-24, 17, and 15 kD. PSII efficiency and the content of chlorophylls (a and b) were significantly lower in the virus-infected leaves.