Recovery of root growth and physiological characters in cotton after salt stress relief

Crop growth in a saline environment depends on its tolerance to salt stress and capacity to recover after salt stress relief. To evaluate recovery mechanisms in cotton after salt stress relief, the changes of plants growth, root vigor, lipid peroxidation, antioxidant enzymes activity, organic solutes in root after salt stress relief were studied for two cotton (Gossypium hirsutum L.) cultivars (Lumianyan 37 and Sumian 22) grown under control (salt content of soil grown cotton was maintained at 0.2%), salt stressed (salt content of soil grown cotton was maintained at 0.5%) and salt recovered (salt content of soil grown cotton was reduced from 0.5% to 0.2% level at the 57 d after seeding) conditions. The results showed that root and shoot growth rate and root vigor significantly increased after salt stress relief, and the increase in growth rate and root vigor was more pronounced in 'Lumianyan 37'. In salt-recovered root, malondialdehyde (MDA) content decrease, the activities of superoxide dismutase (SOD) and peroxidase (POD) decreased, but catalase (CAT) activity increased compared with those in the salt-stressed root. For salt-recovered root, MDA content and POD activity of 'Lumianyan 37' was lower, while the SOD and CAT activities were higher. Salt-recovered cotton root showed a decrease in soluble sugar and free amino acid content compared with the salt-stressed root, especially in 'Lumianyan 37'. The results indicated that growth and root metabolism of cotton plants gradually recovered after salt stress relief, and the high capacity of cotton plants to recover after salt stress relief may be related to the high capacity of antioxidative system and the high utilization capacity of organic solutes as important nutritional components in root.