Abstract:
Abstract: Drought and flood are important abiotic stresses negatively affecting plant growth and development. In recent years, the frequent occurrence of drought-flood abrupt alternation (DFAA) has made crops often need to bear double stresses of drought and flood. In order to explore the response of rice yield to the double stresses of DFAA, a field experiment was conducted using a mid-season Indica hybrid rice cultivar of II U 898 which is cultivated widely in Huaibei plain with 22 treatments of different drought degrees (50%, 60%, 70% field water-holding rate), different drought time (5, 10, 15 d), different submergence depths (1/2, 3/4, whole plant height) and different flooded time (5, 7, 9 d) in 2016. Twenty-two treatments included 6 treatments with drought followed by no flood (DC), 6 treatments with flood followed by no drought (FC), 9 treatments with DFAA and 1 treatment without drought and flood (CK). At drought stage, the barrels are moved to the side of flooded pool, and their weights are measured at 7:00 am and 6:00 pm daily. The barrels are added with water to meet the requirements of drought stress control. In order to avoid the impact of rain, the shelter is used in advance according to the weather forecast. At flood stage, the barrels are moved to different ladders of flooded pool according to the requirements of different submergence depths. The water level of flooded pool is measured with a ruler at 9:00 every morning, and a certain amount of water is irrigated so that the barrels are able to maintain different submergence depths. In case of rainy days, the flooded pool was drained timely to meet the requirements of flood stress control. The barrels of normal treatment have been placed on the top ladder of flood pool, keeping 2-3 cm water level. The compensation effect of the interaction between drought stress and flood stress on rice yield is calculated. The reason of reduction in yield under the interaction between drought and flood is analyzed, and the effect of the interaction on yield components is explored. It's shown from the results that, compared with the normal group, the yield of DFAA group of combination of heavy drought and heavy flood was reduced by 30.3%, and the total grain number was decreased above 30% under long-term heavy drought, while the 1000-grain weight and seed setting rate of each treatment group were close to or higher than the normal group. Besides, compared with the drought group, the yield and total grain number of DFAA group (heavy flood) were reduced above 30% and 33.9%-35.2%, and 1000-grain weight and seed setting rate of DFAA group (short-term light flood) could respectively compensate for 33.6% and 37.6% compared with the drought group (long-term heavy drought). At last, compared with the flood group, the yield of DFAA group (long-term light drought) could compensate for 113.0% compared with the flood group (long-term heavy flood), the total grain number of DFAA group (heavy drought) was reduced by 31.9%-33.7% compared with the flood group (heavy flood or long-term light flood), and the 1000-grain weight and seed setting rate of DFAA group (long-term drought) could compensate for 79.7%-118.4% respectively compared with the flood group. The research results can provide a reference for exploring the mechanism of DFAA and disaster mitigation measures.