| Water is the main factor limiting the improvement of rice productivity in most regions of the world.With the increasing shortage of water resources worldwide and the worsening drought caused by climate change,improving water use efficiency(WUE)has become an urgent problem in agriculture production.Rice is the largest water user in agriculture,and its irrigated area accounts for 75%of the world’s rice planting area.Every year,rice production is reduced due to drought and water shortage.Improving rice water use efficiency,developing water-saving agriculture and alleviating the contradiction between supply and demand of water resources are important issues to ensure food security.In this study,the typical indica rice varieties in Jiangsu Province in recent 80 years were used as experimental materials,and alternate wetting and drying irrigation(AWD)and conventional irrigation(CI)were used during the whole growth stages.The effects of different irrigation methods on grain yield,water use efficiency,grain quality,aboveground and root morphological and physiological characteristics were analyzed.The main results are as follows:1.Grain yield and water use efficiencyThe grain yield and yield water use efficiency(WUEy)of all varieties increased gradually with the improvement of varieties.The increase of yield was mainly due to the increase of the number of total spikelets.Compared with CI,AWD significantly increased the yield of all varieties and WUEy.Grain yield increased by 20.05%,16.39%,9.84%and 9.50%,respectively.WUEy increased by 68.69%,65.79%,55.24%and 56.10%,respectively.The results indicated that there were differences between varieties in yield and WUEy’s response to irrigation.Although AWD decreased the number of panicles,it simultaneously increased spikelets per panicle,filled grains rate and 1000-grain weight,and finally increased grain yield.2.Aboveground characteristicsThe number of tillers,shoot dry weight,leaf area index(LAI)at heading stage,photosynthetic rate,transpiration rate and leaf water use efficiency(WUE1)of all varieties increased gradually with the improvement of varieties.Compared with CI,AWD increased the number of tillers,shoot dry weight,WUE1,photosynthetic rate,transpiration rate and LAI at heading at each main growth stage of rice.The response of modern semi-dwarf hybrid rice to AWD was more significant than that of other types.3.Grain quality and starch propertiesWith the improvement of the varieties,the milled rice rate,head milled rice rate,protein content,activities of key enzymes involved in sucrose-to-starch conversion in grains,the starch solubility and swelling capacity were significantly increased.Compared with CI,AWD improved the milling and appearance quality of rice,increased the peak viscosity,hot viscosity,final viscosity and breakdown of rice starch,and decreased the setback and relative crystallinity of rice starch.4.Root morphology and physiological characteristicsThe root dry weight,root-shoot ratio,root length,root diameter,root oxidation activity,root total absorbing surface area and active absorbing surface area,zeatin(Z)+zeatin nucleoside(ZR)contents in roots,Z+ZR and abscisic acid(ABA)contents in root bleeding increased gradually with the improvement of rice varieties at each main growth stage.Compared with CI,the above indexes of the main growth stages of rice were improved under AWD.Modern varieties responded more positively to AWD,indicating that root morphology and physiological characteristics of modern varieties were significantly improved under AWD. |
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