| Heilongjiang is the dominant rice production area in China,and has always ranked among the top in rice cultivation area and total production.However,as water shortage becomes more and more serious,scholars at home and abroad pay more and more attention to the research of watersaving irrigation technology.The alternate wet and dry irrigation is one of the most widely used water-saving irrigation technologies with the most obvious water-saving effect.The research on alternate wet and dry irrigation in Heilongjiang Province is of great significance to improve the water use efficiency of rice as well as to promote the sustainable development of rice.Irrigation with alternating wet and dry irrigation during the filling period is an important period for rice yield formation,which can promote grain filling,reduce empty and deflated grains,and regulate rice yield formation.Therefore,in this study,Dongnong 427 and Longdao 18 were used as test materials,and normal irrigation was used as the control(D0),and four irrigation treatments were set up during the filling period,with alternating wet and dry irrigation(D1)throughout the filling period,alternating wet and dry irrigation(D2)starting 15 days after tasseling,alternating wet and dry irrigation(D3)starting 25 days after tasseling,and alternating wet and dry irrigation(D4)starting 35 days after tasseling,To systematically study the effects of alternating wet and dry irrigation at the stage of grain filling and setting on photosynthetic characteristics of rice functional leaves,the activities of key enzymes of carbon metabolism and non-structural carbohydrate content of strong and vulnerable grains,dry matter accumulation and distribution,seed filling characteristics and yield,Investigating the change pattern of alternate wet and dry irrigation during the period of filling and setting on photosynthetic characteristics of rice functional leaves and the accumulation of non-structural carbohydrate formation in strongly vulnerable grains,aiming to clarify the optimal dry and wet alternate irrigation method for cold japonica rice during the filling and fruiting period,Revealing the relationship between carbon metabolism and yield formation,To provide a theoretical basis for the study of alternate wet and dry irrigation and the establishment of water-saving cultivation patterns for rice in Heilongjiang Province.The results of this experiment are as follows:1.The chlorophyll content,ribulose 1,5 diphosphate(Ru BP carboxylase activity),phosphoenolpyruvate(PEP carboxylase activity),net photosynthetic rate(Pn),transpiration rate(Tr),and intercellular carbon dioxide concentration(Ci)of Dongnong 427 and Longdao 18 functional leaves showed a decreasing trend after flush.Compared with D0,the above indicators were significantly lower in D1 and D2 treatments,non-significantly different in D3 and D4 treatments,and significantly higher in D3 than in D1 and D2 treatments.Compared with D0,the chlorophyll content and photosynthetic characteristic parameters and photosynthetic key enzyme activities decreased at a higher rate in the alternating wet and dry irrigation treatment of Longdao 18 than in Dongnong 427.2.The functional leaf sucrose content,soluble sugar content and functional leaf sucrose phosphate synthase(SPS)and sucrose synthase(SS)of both varieties showed a trend of increasing and then decreasing after spikelet flush,The above indicators peaked at 20 days after flush in D1 treatment and at 25 days after flush in the remaining treatments.Compared with D0,the functional leaf sucrose content and soluble sugar content of D1 and D2 treatments were significantly higher,the functional leaf sucrose content and soluble sugar content of D3 treatment were significantly lower,the functional leaf sucrose content and soluble sugar content of D4 treatment were not significantly different,and the functional leaf sucrose content and soluble sugar content of D3 treatment were significantly lower than those of D1 and D2 treatments.Compared with D0,SS activity and SPS activity in functional leaves of D1 and D2 treatments were significantly lower,SS activity and SPS activity in functional leaves of D3 treatment were significantly higher,and the differences in SS activity and SPS activity in functional leaves of D4 treatment were not significant;SS activity and SPS activity in functional leaves of D3 treatment were significantly higher than those of D1 and D2 treatments.Compared with D0,the increase of sucrose content and soluble sugar content in functional leaves of Longdao 18 with alternate wet and dry irrigation was higher than that of Dongnong 427,and the decrease of SPS activity and SS activity in functional leaves of Longda18 with alternate wet and dry irrigation was higher than that of Dongnong 427.3.The sucrose content and soluble sugar content of the strong grains of the two varieties showed a gradual decline after spikelet flush,while the weak grains showed a rising and then decreasing trend with the advancement of the filling process,and the weak grains reached their peak at 15 days after spikelet flush.Compared with D0,the sucrose content and soluble sugar content of the seeds in D1 and D2 treatments were significantly higher,the sucrose content and soluble sugar content of the seeds in D3 treatment were significantly lower,and the difference between the sucrose content and soluble sugar content of the seeds in D4 treatment was not significant;the sucrose content and soluble sugar content of the seeds in D3 treatment were significantly lower than those in D1 and D2 treatments.The SPS activity and SS activity of strong and weak grains of both varieties showed a trend of increasing and then decreasing after flush.Compared with D0,SS activity and SPS activity in D1 and D2 treated grains were significantly lower,SS activity and SPS activity in D3 treated grains were significantly higher,and SS activity and SPS activity in D4 treated grains were not significantly different;SS activity and SPS activity in D3 treated grains were significantly higher than those in D1 and D2 treatments.Compared with D0,the increase of sucrose content and soluble sugar content in the seeds of Long Rice 18 with alternate wet and dry irrigation was higher than that of Dongnong 427,and the decrease of SPS activity and SS activity in the seeds of each treatment of Long Rice 18 was higher than that of Dongnong 427.4.The differences in straight-chain starch,branched-chain starch and total starch contents of the strong grains between the treatments of the two varieties were not significant,while the differences in branched-chain starch and total starch contents between the treatments of the weak grains were significant.Compared with D0,amylopectin content and total amylose contents of vulnerable grains were significantly lower in D1 and D2 treatments,significantly higher in D3 treatment,and not significantly different in D4 treatment;amylopectin content and total amylose contents of D3 treatment were significantly higher than those of D1 and D2 treatments.Compared with D0,the activities of adenosine diphosphate pyrophosphorylase(AGPase pyrophosphorylase),soluble starch synthase(SSS),starch branching enzyme(SBE),and starch debranching enzyme(DBE)were significantly lower in the disadvantaged grains treated with D1 and D2,while the activities of AGPase,SSS,SBE,and DBE were significantly higher in the disadvantaged grains treated with D3,and the activities of AGPase,SSS,SBE,and DBE in the disadvantaged grains treated with D4 were not significantly different from D0,The AGPase,SSS,SBE and DBE activities of vulnerable grains were significantly higher in D3 treatment than in D1 and D2 treatments.The increase of AGPase,SSS,SBE and DBE activities in the seeds of Dongnong 427 treated with alternate wet and dry irrigation was higher than that of Longdao 18,and the decrease was smaller than that of Longdao 18.5.The effect of alternate wet and dry irrigation on above-ground dry matter accumulation and distribution of rice during the filling and setting period was significant.The amount of dry matter accumulation in seeds of D1 and D2 treatments was not significantly different from that of D0treatment;D3 treatment was significantly higher than D0 and other treatments,and D4 treatment was significantly higher than D0 treatment,but significantly lower than D3 treatment.Dongnong427 had strong dry matter accumulation and translocation ability,and the increase in total aboveground dry matter accumulation and seed dry matter accumulation was greater than that of Longdao 18.6.The maximum filling rate(GRmax)and mean filling rate(GRmean)of rice strong and weak grains differed significantly between treatments,which were D1>D2>D3>D4>D0.The time to reach the maximum filling rate(Tmax)and the active filling period(D)of rice strong and weak grains differed significantly between treatments(except for the D4 treatment which was not significantly different from the D0 treatment),and each treatment showed D3>D4>D0>D2>D1.The effect of alternate wet and dry irrigation during the filling and setting period on the filling process of weak grains was significantly greater than that of strong grains.7.The differences in spike length,effective spike number,total number of grains per spike,number of primary branch stalks,and number of secondary branch stalks between treatments were not significant for the two varieties of rice,and the differences in the number of secondary branch stalks empty shells between treatments were significant(except for the non-significant differences between the D4 treatment and the D0 treatment),which were D1>D2>D0>D4>D3;Significant differences were found between the treatments of the two varieties in fruiting rate and thousand grain weight(except for the D4 treatment where the differences in fruiting rate and thousand grain weight were not significant with the D0 treatment),and the treatments showed D3>D4>D0>D2>D1.8.The differences between the two varieties of rice yield treatments were significant(except for the yield of D4 treatment which was not significantly different from D0 treatment),which showed that D3>D4>D0>D2>D1,and D3 treatment was significantly higher than D0 and other treatments.Compared with D0,the water use efficiency of each treatment was significantly higher and differed significantly between treatments,which showed that D1>D2>D3>D4>D0.The water use efficiency of D3 treatment was significantly lower than D1 and D2 treatments,but significantly higher than D0 and D4 treatments. |
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