Influence of rewatering on compensatory effect of maize seedling roots with diluted seawater irrigation

In order to use seawater as supplement water to realize water-saving irrigation in coastal areas, taking the resistant maize “Nongda 108” as study object, some compensatory characteristics related to the roots of seedlings were studied under different treatments. Firstly the seedlings were irrigated with different salinity seawater, then irrigated with freshwater and lastly treated with polyethylene glycol (PEG) solution to simulate the drought stress. The results indicated that, under the irrigation of sustained 25% seawater and alternate 25% seawater-50% seawater respectively, the proline content and superoxide dismutase activity were obviously increased, the contents of soluble sugar and potassium ion (K+), root activity and relative water content (RWC) and ratio of root/top slowly increased, but malondialdehyde (MDA) contents quickly decreased. After rewatering, K+ content, root activity and RWC raised apparently, and other determinants declined. During the PEG stress, MDA content and root activity showed a little decrease, and else indexes dramatically increased. Compared with freshwater treatment, the compensatory effect of rewatering after sustained 50% seawater stress was evidently debased due to severe root damage, and that of sustained 25% seawater treatment was lessened inapparently, but that of alternate 25% seawater-50% seawater irrigation was enhanced a little or markedly. This implied that seedlings were induced by the optimized seawater stress, which led to corresponsive metabolism, and the rewatering caused compensatory even “over-compensatory” metabolism and drought-resistance in the root, which also alleviated sub-stress effects on seedlings to the salinity.