Responses of different peanut cultivars to drought and waterlogging stress and physiological mechanism

To evaluate the responses of peanut to drought and waterlogging stresses, biomass of shoot and root, root-shoot ratio, root activity, SOD activity and MDA content in leaves at seedling and flowering-pegging stages were determined. A pot experiment with four different drought-waterlogging tolerance cultivars was conducted in rainproof greenhouse. Four water treatments were carried out as follows: normal irrigation (CK), drought (7d, leaf wilting), root waterlogging (1d, 3d and 7d, 2cm of water-depth over soil surface) and whole plant waterlogging (1d, 3d and 7d, water-depth over the canopy of plant). The results showed that drought stress decreased shoot dry biomass (SDB) and increased root-shoot ratio (RSR) at seedling and flowering-pegging stages, reduced root dry biomass (RDB) at seedling stage whereas elevated at flowering-pegging stage. Waterlogging stress accelerated SDB, reduced RDB and RSR at both stages, and the effects of it aggravated with increase of water level and progress of time. For all cultivars, root activity decreased, but SOD activity and MDA content in leaf increased under drought and waterlogging conditions. After same time (7d) of water stresses, damage suffering from drought was much heavier than that from waterlogging, while that at flowering-pegging stage was much heavier than at seedling stage. Comprehensive analysis based on changing of biomass and physiological indexes further revealed that there was large difference in drought and waterlogging tolerance among cultivars: Xianghua 55 had higher tolerance to drought and lower to waterlogging, Yuhua 15 had lower tolerance to drought and higher to waterlogging, Zhonghua 4 had the lowest tolerance to the two stresses, while Zhonghua 8 had the highest.