关键词: 盐胁迫, 鼠李糖脂, 根系形态, 生理特性, 综合评价

Abstract:

To investigate the mitigating effect of rhamnolipids （RLS） on the physiological growth of cotton seedlings under salt stress， 2 salt gradients including low salt （3 g·L^-1 NaCl， T₁） and high salt （6 g·L^-1 NaCl， T2） and 4 RLS gradients including 0（R₀）， 200（R₁）， 300（R₂） and 400 mg·L^-1 （R₃）were set up to analysis the effects of RLS on the root morphology， antioxidant enzymes and osmoregulatory substances of cotton seedlings under salt stress. The results showed that the appropriate level of RLS under salt stress could promote the growth of total root length， root surface area and root tip number of cotton seedlings. Under low salt stress， the activities of superoxide dismutase （SOD）， peroxidase （POD）， catalase （CAT） and contents of proline （Pro）， soluble sugars （SS） in the roots of cotton seedlings firstly increased and then decreased with the increase of RLS content，with T₁R₂ showing an increase of 14.0%， 15.2%， 28.8%， 28.5% and 19.5%， respectively， compared with T₁R₀. The activities of SOD， POD， CAT and contents of Pro，SS in the roots of cotton seedlings under high salt stress showed a gradual decrease under high salt stress， with T₂R₁ treatment increasing 10.5%， 12.6%， 13.9%， 21.7% and 4.8%， respectively， compared with T₂R₀. Principal component analysis showed that the response of cotton seedling root surface area， SOD and Pro to the regulation of RLS under salt stress was high， and could be used as the main control indicators for the physiological growth regulation of cotton seedlings by RLS under salt stress. The optimum content of RLS applied under low salt stress to enhance the salt tolerance of cotton seedlings was 300 mg·L^-1， while the optimum content of RLS applied under high salt stress was 200 mg·L^-1. Above results provided a more suitable exogenous application strategy for cotton salt tolerance and stress tolerance planting.

Key words: salt stress, rhamnolipids（RLS）, root morphology, physiological and biochemical properties, comprehensive evaluation