Antioxidant Enzyme Activities and Abiotic Stress Tolerance Relationship in Vegetable Crops

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. Both the whole plant and in vitro callus culture experiments gave similar results. Antioxidant enzymes can be useful for screening to determine the tolerant and sensitive plant genotypes against abiotic stresses

Comparison of salinity effects on grafted and non-grafted eggplants in terms of ion accumulation, MDA content and antioxidative enyzme activities

Grafting onto resistant/tolerant rootstocks is known to alleviate the negative effects of abiotic stress factors like salinity by enhancing their enzymatic antioxidant defense system and having more efficient nutrient uptake. This study was carried out under greenhouse conditions, different rootstock/scion eggplant combinations were grown under two salinity treatments 1.8-2 dS/m (control) and 6-7 dS/m (stress) with seven eggplant genotypes as rootstocks (commercial and Turkish genotypes). Two genotypes were used as the scion. Leaf MDA and ions (Na+, Cl-, K+ and Ca++) content, antioxidant enzymes activity were evaluated as indicators for plant tolerance level. It was found that the rootstock-grafted plants were more efficient in preventing Na+ ions to be transferred to the plants upper parts and had higher SOD, CAT, and APX activity levels compared to the self- and non-grafted plants which resulted in better tolerance and growth in these plants

The effect of irrigation water including Cu, Pb, Cd, and Zn on the physiological and biochemical parameters in eggplant genotypes tolerant or susceptible to some abiotic stress factors

The eggplant genotypes (Burdur Merkez, Burdur Bucak, Kemer ve Giresun) of which salt and drought tolerances were determined before by examining changes in some of the morphological and physiological characteristics were used as materials. In the studies carried out in controlled greenhouse conditions, eggplant plants were subjected to different levels heavy metal irrigation at 20 days after sowing (Control: 0 ppm; I. mixture: 0.2 ppm Cu+0.01 ppm Cd+5 ppm Pb+2 ppm Zn; II. mixture: 0.4 ppm Cu+0.02 ppm Cd+10 ppm Pb+4 ppm Zn). Young plants were harvested after forty days at heavy metal treatment and the fresh and dry shoot weight, fresh and dry root weight, shoot and root length, leaf areas, chlorophyll, malondi-aldehyde (MDA), superoxide dismutase (SOD) and glutathione reductase (GR) were determined. The eggplant plants were adversely affected by heavy metal applications. In parallel to increase the dose, heavy metal mixtures led to a reduction in values of fresh and dry weight of shoot and root, stem and root length, leaf area. MDA and antioxidative enzyme activities increased in plants irrigated with water containing a mixture of heavy metal. As a result of this study, tolerant Burdur Merkez and Burdur Bucak genotypes showed a better performance compared with the salt sensitive genotypes Giresun and Kemer. The plants are thought to use similar mechanisms for resistance to abiotic stresses such as drought and heavy metal stress

comparative study with commercial rootstocks to determine the tolerance to heavy metal (Pb) in the drought and salt stress tolerant eggplant breeding lines

Negative effects of heavy metals on plants are peroxidation of lipids in cell membranes, production of free oxygen radicals, disorders in photosynthesis, damages in DNAs and as a result death of the cell. Plant development, productivity and quality of the fruits are decreased in the plants that are exposed to Pb stress which is one of the most toxic heavy metals. Usage of rootstocks which is mainly used against biotic stress conditions also seems to be defined as a solution to abiotic stress conditions such as heavy metal stresses. In eggplant production, wild species and hybrids are used as rootstocks against soil based pathogens and nematode. Reactions of improvement lines derived from local gene resources for rootstock improvement to heavy metal stress which is one of the abiotic stresses were determined. While determining the resistance against Pb stress, commercially used eggplant rootstocks are compared. In this study 4 eggplant cultivars (S. melongena: Burdur Bucak, Mardin Kızıltepe, Artvin Hopa and Kemer) whose resistance potential against salt and drought stresses had been previously revealed and 6 rootstocks of wild eggplant species or hybrids (AGR-703, Doyran, Hawk, Hikyaku, Köksal-F1 and Vista-306) were tested against Pb stress. Eggplant seedlings were applied to 0, 150 and 300 ppm Pb solutions (Pb(NO3)2) during 4-5 true leaf stage. 20 days after the stress application wet and dry weight of green parts and roots, height of the body part and leaf areas were measured. Pb tolerance of Köksal F1 and AGR703 rootstocks were higher than other commercial rootstocks. Mardin Kızıltepe and Burdur Merkez genotypes which have high tolerances against abiotic stress gave lower values with respect to Artvin Hopa and Kemer which are sensitive genotypes and many other rootstocks while comparing the reduction ratios of stress signs such as shoot fresh weight and shoot length according to control under Pb stress