Effects Of Soil Drought Stress On Root Growth, Stomatal Characteristics And Antioxidant Enzume Of Tomato Crops

Tomato is one of the largest acreage vegetables in the world, also China’s major facilities vegetable crops. The growth of tomato demands a lot of water. Drought stress directly affect the process of physiological metabolism and yield formation of tomato. In order to study the effect of various water supply on greenhouse tomatoes in different growth stage, a research has been conducted in Nanjing University of Information Science and Technology. Taking tomato (Solarium lycopersicum cv. ’Jinfen 2*) as the plant material. The experiment was taken in the stage from growth to seeding of facility tomato. Root indicators, morphological index,stomatal charact-eristics and protective enzymes activity of leaf were measured during different growth stage. Four soil moisture treatments were designed, i.e., normal water supply treatment (T1), mild water stress treatment (T2), moderate water stress treatment (T3) and severe water stress treatment (T4). The main findings are as follows:(1) The results showed that among different soil moisture treatments, the maximum total root length, total root surface area, average root diameter and number of root tips of tomato plants were in order of T2, T1, T3 and T4 from high to low. Under the treatment of T1, T2 and T3, tomato roots distributed mainly in 5-10 cm soil layer, while in 15-25 cm layer under T4. The plant height, stem diameter and leaf area index (LAI) of tomato plants decreased with the reduction of soil moisture.(2) The results showed that the stomata length, width, aperture and open ratio of the leaves decreased with the increase of water stress. And with the extension of stress time, the reduction amplitude increased. The stomatal length and width of tomato decreased synchronously. Compared with the stomatal width, the stomatal length was more significantly with the increase of water stress. The stomata shape gradually changed from long ovate to suborbicular. The stomatal density of the upper epidermis increased gradually with the extension of drought stress time, while the stomatal density of the lower epidermis presented a trend of decreasing at first and then increasing.(3) With water stress time increased, SOD, POD, CAT activity and MDA content had different degrees of increase. Among the four water stress treatment, the maximum value of SOD, POD, CAT activity and MDA content were appeared in the seeding stage of tomato. Moreover in the same period SOD, POD, CAT activity presented trend of T1>T2>T3>T4 while MDA content was expressed as T4>T3>T2>T1, besides there were significant differences between different treatments.From the above, comparison the variety of tomato indicators in four water stress treatment. Mild water stress treatment did not significantly affect the growth of above-ground part, while benefited the root growth. Moderate and severe water stress treatment significantly inhibited the growth of above-ground part and decreased the roots distribution layers in soil. Appropriate water stress during the seeding stage of tomato could promote the growth of root, improve the drought resistance of tomato, While the severe drought will cause harm to tomato.