Climatic changes can cause serious reductions in yield and crop quality. Under the threat of climatic changes, one of the precautions to cope is selection and development of resistant vegetable genotypes to abiotic stresses. Several physiological and biochemical reactions and different tolerance levels can occur according to plant species. When plants are subjected to environmental stresses such as salinity, drought, temperature extremes, herbicide treatment and mineral deficiency, the balance between the production of reactive oxygen species ROS and the quenching activity of antioxidants is upset, often resulting in oxidative damage. Since activated oxygen species can disrupt normal metabolism through oxidative damage to lipids, protein and nucleic acids, plants possess a number of antioxidant enzymes that protect them from these cytotoxic effects. To control the level of ROS and to protect cells under stress conditions, plant tissues contain several enzymes for scavenging ROS. The high levels of antioxidative enzyme activities were determined in the tolerant genotypes of tomatoes, eggplant, peppers, cucumbers, melons, squash, beans, okra, etc. to several abiotic stress factors. "oth the whole plant and in vitro callus culture experiments gave similar results. "ntioxidant enzymes can be useful for screening to determine the tolerant and sensitive plant genotypes against abiotic stresses.

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Vermicompost can play an effective and important role in plant growth and development and also in reducing harmful effects of various environmental stresses on plants. The vermicompost fertilizer application was evaluated for the growth, physiological and biochemical parameters of lettuce (Lactuca sativa var. crispa) plants under drought stress conditions. Tests were carried out at different levels of vermicompost (0, 2.5 and 5%) and drought stress [no stress, moderate drought, and severe drought at 100, 50 and 25% of field capacity]. In comparison to control (vermicompost at 0%), lettuce plants treated with vermicompost at 2.5 or 5%  had higher shoot height, shoot fresh weight, relative water content, stomatal conductance, chlorophyll a, chlorophyll b , total chlorophyll and carotenoid contents under moderate and severe drought stress conditions. Malondialdehyde (MDA) content and superoxide dismutase (SOD) and catalase (CAT) activities increased while plants under drought stress conditions. Application of vermicompost caused higher SOD and CAT enzyme activities and lower MDA content under drought stress. Enhancement in antioxidant enzyme activities as a result of vermicompost destroyed reactive oxygen species. Therefore, application of vermicompost under moderate and severe drought stress decreased MDA content in lettuce plant cells. Data indicated a positive effect of the vermicompost on the growth of lettuce under drought stress conditions.

This study was carried out to determine the changes in chlorophyll and ion contents, lipid peroxidation level, and antioxidative enzyme activities of 4 eggplant genotypes (Mardin Kızıltepe (MK), Burdur Merkez (BM), Artvin Hopa (AH), and Kemer (K)) with different salt tolerance levels under drought stress. Experiments were conducted in a greenhouse with controlled climatic conditions. When the plants reached the 3-4 leaves stage, 3 different treatments were applied to create the drought levels. The first condition in the study was obtained through control application treatment (D 0 ), which was depletion of 40% of the available water holding capacity. The second application (D 1 ) was depletion of 90% of the available water holding capacity. The third application (D 2 ) was no applied irrigation water. Plants were analyzed with regards to chlorophyll and ion contents, lipid peroxidation levels, and antioxidative enzyme activities. Significant differences were observed among interactions of genotypes and levels of drought stress in chlorophyll and ion (K + , Ca 2+ , Zn 2+ , Mn 2+ , and Fe 2+ ) contents, lipid peroxidation levels, and activities of antioxidant enzymes (superoxide dismutase-SOD, catalase-CAT, glutathione reductase-GR, and ascorbate peroxidase-APX). The chlorophyll and ion contents of eggplant genotypes under drought stress decreased. However, different levels of lipid peroxidation and antioxidative enzyme activities were observed. The situation changed depending on genotypes. Lipid peroxidation levels increased under drought stress, especially in salt-sensitive genotypes (AH and K). On the other hand, the activities of antioxidative enzymes in the salt tolerant MK and BM genotypes significantly increased. With regard to the investigated traits, salt-tolerant genotypes were also found to be quite tolerant against drought stress.

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