Effect Of Water-saving Irrigation On Assimilate Distribution And Yield Formation In Different Rice Varieties

Rice is one of the most important grain crops in China.At the same time,it is also the most fresh water consuming crop.In recent years,regional and seasonal droughts have frequently occurred,and the further increase of rice yield is facing a severe challenge.By combining the advantages of different rice varieties with reasonable water management regimes,coordinating the relationship between yield and water use efficiency,increasing the water use efficiency of rice meanwhile reducing the compensation for the loss of production has become an urgent situation to be solved.In order to explore the regularity of yield formation of different rice varieties under water-saving irrigation,field experiments were conducted with three different rice cultivars,water-saving and drought resistant rice Hanyou 113(HY113),high yield rice Yangliangyou 6(YLY6)and Yongyou 4949(YY4949)and three irrigation regimes;traditional flooding irrigation(F),alternate wetting and drying(AWD)and drought(D)treatments in 2016-2017 years to study the agronomic characters,photosynthetic characteristics and assimilates distribution of rice.The relationship between photosynthetic characteristics and the accumulation and distribution of assimilates with yield and yield components,rice quality and water use efficiency were further analyzed.The main results were as follows:1.Compared with F treatment,the growth stage increased by 3 and 6 days under the AWD and D respectively.Under the AWD,the reproductive periods of YLY6 was 5 days longer than that of HY113 and YY4949,and YLY6 plant height at full heading stage was significantly higher than that of HY113 and YY4949;under D treatment,the plant height significantly decreased at booting stage and full heading stage,meanwhile the lodging resistance of the plants significantly increased.And the bending moment,the length of the first and the second internode of the base and the outer diameter of the base of all cultivars were significantly decreased under D treatment.2.Compared with F treatment,the Air-leaf Temperature Gap(ALTG)at milky stage was significantly decreased under AWD treatment,where as ALTG was significantly lower at full tillering stage under D treatment.The ALTG of YLY6 was significantly higher than that of YY4949 at milky stage under AWD treatment,and significantly lower than the HY113.Leaf area,leaf area index,stomatal conductance and transpiration rate of YLY6 were significantly higher than those of HY113 at milky stage.3.Compared with other treatments,dry matter accumulation and harvest index of YLY6 increased significantly under AWD treatment at milky stage,and during the late reproductive stage(from milky stage,to mature stage),YLY6 had higher stem sheath(46%)and leaf(54%)dry matter output conversion rate,and there were higher sucrose synthase and sucrose phosphate synthetase activity of leaf in YLY6 at milky stage.And at mature stage,the soluble sugar content of the stem sheath of YLY6 was significantly lower than that of YY4949 and the starch content of the stem sheath was significantly lower than that of HY113 and YY4949,and the starch content of the grain was significantly higher than YY4949 while significantly lower than HY113.4.Compared with F treatment,the rice yields were increased by 3.22%-20.27% under AWD treatment,while the yield significantly decreased under D treatment,because of the significantly declined in grain number per panicle.And compared with other treatments,the yield and the number of effective panicles of YLY6 were significantly increased under AWD treatment.Under the F treatment,the yield of YLY6 was significantly higher than that of HY113,and the yield of HY113 was significantly higher than that of YY4949,mainly because the filled grains of YLY6 was significantly higher than that of HY113 and YY4949.Under D treatment,the yield of YLY6 was significantly higher than that of HY113,and the yield of YLY6 was higher by 9.30% than that of YY4949.The filled grains of YLY6 under D treatment was significantly higher than that of HY113 and YY4949.5.The performance of rice quality showed heterogeneity under the water-saving irrigation treatment.Miled rice and head rice were significantly increased,while the content of amylose was significantly decreased,otherwise the chalkiness of YLY6 and YY4949 were significantly increased under AWD and D treatments.While the chalky kernel and chalkiness of HY113 were significantly lower under AWD and D treatments,and the amylose content was significant increased under D treatment.6.Compared with F treatment,irrigation water consumption was reduced by 42.37% and 88.81% under AWD and D treatments,mainly because the average irrigation cycle under AWD and D treatments was respectively prolonged by 3-4 d and 8-9 d.The average amount of irrigation under the AWD and D treatments was reduced by 6.11% and 83.97%,which saved the labor input.Moreover,YLY6 had higher irrigation water consumption than that of HY113 and YY4949 under the three soil water treatments.Water-saving irrigation can significantly improve irrigation water use efficiency of different rice varieties.Under the F treatment,the IWUE of YLY6 is 12.24% and 24.49% higher than that of HY113 and YY4949.Water-saving irrigation treatments could significantly improve the irrigation water use efficiency of different rice varieties.Under AWD treatment,the irrigation water use efficiency of YLY6 was significantly higher than that of HY113 and YY4949,while under D treatment,the irrigation water use efficiency of YLY6 was significantly higher than that of HY113,but was significantly lower than that of YY4949.In summary,the reproductive growth stage of YLY6 was prolonged under AWD treatment,and the net photosynthetic rate at full tillering stage and heading stage were significantly increased under AWD treatment.And there was a higher photosynthetic leaf area,chlorophyll content,sucrose synthase and sucrose phosphate synthase activity at milky stage,which maintained higher photosynthetic production capacity,and had higher dry matter distribution and transport during milky stage.And appropriate starch content of grain supported the formation of yield and quality at mature stage The AWD-YLY6 treatment ensured a higher yield and better quality toghter with significant increase of water use efficiency.So the mode could be used as a water-saving mode for high yield and water-saving cultivation techniques in the Jianghan Plain.