Effect of water stress on protective enzyme system and yield of naked oat (Avena nuda L.).

An indoor study was conducted over two years to determine the impact of drought stress on naked oat protective enzyme system and yield using a quadratic regressive spinning design. The activity of superoxide dismutase SOD was high at early growth stage and the levels gradually reduced as the plants getting mature. Activity of peroxide dismutase POD gradually reduced until jointing or booting stages but increased at anthesis stage before falling down again. For the activity of catalase (CAT), there were two peaks at the jointing and anthesis stages, respectively. CAT activity showed a downward trend with the increase of water stress time and intensity, so it may be used as a suitable indicator of drought stress. By modelling regression and analyzing the best fit, it was concluded that the order of the sensibility of water to yield under different growth duration was anthesis stage > jointing stage > booting stage > grain-filling stage > seedling stage. The highest yields were obtained when oats were maintained at 45% field water capacity FWC at seedling and grain-filling stages, 75 to 90% FWC at jointing stage, 67% FWC at booting stage and 76% FWC at anthesis stage. The results indicated that jointing stage was the most critical stage for oat yield, and more grain yield was obtained when water supply was adequate in jointing and booting stages. From the relationship between protective enzyme system and yield, it is concluded that 60% FWC is critical water requirement threshold under not culture.