DROUGHT STRESS INTENSITY, DURATION AND ITS RESISTANCE IMPACT ON RICE (ORYZA SATIVA L.) SEEDLING

Rice seedlings have a different response to drought stress intensity and duration, which reduces rice seedling growth and grain yield. In the year 2015, a greenhouse experiment was conducted to ascertain the effect of the relationship between drought stress intensity, duration, and drought resistance on rice seedling. Yangliangyou 6 ("super" rice variety) and Hanyou 113 (drought-resistance rice variety) were subjected to polyethylene glycol (PEG6000)-induced water stress. Drought stress intensities i.e. 10%, 15%, 20% and 25% PEG6000 with 4 d, 8 d or 12 d after emergence at 21 days was imposed, respectively. Control (0% PEG6000) was used for comparison. Drought dehydration factor (DDF) and root induction factor (RIF) increased with drought duration. In each drought stress duration, RIF, drought tolerance factor (DTF) and DDF were raised under moderate drought stress intensity (10-15% PEG6000), the advantage of DDF and DTF was shown at 12 d drought duration under severe drought stress intensity (20-25% PEG6000). Thus, drought stress intensity significantly negatively affected rice seedling growth compared with drought stress duration. Improvement in DDF and RIF enhanced rice seedling growth under moderate drought stress conditions, while severe drought stress positively stimulated DDF and DTF which resulted in improved rice seedling growth.