| Heilongjiang Province is an important japonica rice production area in China,made great contributions to meet the demand of rice market and ensure the security of grain.The booting stage is the critical period of rice water demand,when drought stress seriously affects rice yield and quality.Nitrogen metabolism is one of the important physiological processes of plant life activities,which has an important influence on rice growth and development,yield,and protein formation.In this study,two japonica rice,Songjing 6(no drought tolerance)and Dongnong 425(drought tolerance)were used as materials to understand the effects fof drought stress at booting stage on the nitrogen metabolism and yield in rice in cold-region,with there treatments of irrigation method((soil water potential:-10,-25 and-40 kpa,respectively),normal irrigation as a control.The effects of drought stress at booting stage on nitrogen metabolism key enzyme activity,soluble protein content,proline content,grain protein and components content and yield of japonica rice in cold region were studied.It is urgent to clarify the response mechanism of nitrogen metabolism under drought stress at booting stage and the differences among varieties,and revealed the regulatory role of nitrogen metabolism key enzyme activities on grain protein and protein components,in order to enrich the physiological basis of drought resistance of Japonica rice in cold region at booting stage.The main conclusions of this experiment are as follows:1.Compared with the control,the activities of nitrate reductase(NR),glutamine synthetase(GS),glutamate synthetase(GOGAT),glutamate-pyruvate transaminase(GPT),and glutamate-oxaloacetate transaminase(GOT)of Songjing 6 and Dongnong 425 in functional leaves during mild drought 5-15 d stage were increased,but the rise decreased in time of drought stress,then decreased after 20 days of mild drought,increased after rewatering treatment,and the rise gradually decreased.While the enzyme activity decreased under moderate and severe drought(Dongnong 425 GS,GOT at moderate drought 5d and NR,GOGAT,GPT increased at moderate drought 5-10 d),then the decline decreases after rewatering treatment.The activity of glutamate dehydrogenase(GDH)in functional leves increased with the more serious of drought stress,the risw gradually increased,and the rise decreased after rewatering.Furthermore,the activities of nitrogen metabolism key enzymes in functional leaves of Dongnong 425 were higher and the resilience was stronger than that of Songjing 6.2.Compared with the control,the activities of GS,GOGAT,GPT and GOT in grain were significantly increased under mild drought.Under moderate drought,GS,GOGAT,GPT and GOT increased in the early stage of filling(7-14 d after full heading)and then decreased of Dongnong 425;The activities of Songjing 6 GS and GOGAT increased during the early stage of filling(7 d after heading),then decreased,while GPT and GOT activities decreased during the whole grain filling period.Under severe drought,the activities of GS,GOGAT,GPT and GOT decreased,which was significantly lower than that of moderate drought.Compared with the control,the activity of GDH increased with the more serious of drought stress.Furthermore,the activities of nitrogen metabolism key enzyme of Dongnong 425 were higher than that of Songjing 6.3.Compared with the control,the soluble protein content of functional leaves increased under drought stress.The content increased with the serious of drought in the drought treatment 5-10 d of Songjing 6,and under severe drought content was lower than moderate drought after 15 days of drought treatment.However,the content of Dongnong 425 increased in 5-15 days of drought stress and the severe drought was lower than moderate drought after 20 d drought treatment.The content of proline in functional leaves of cold-region rice increased significantly with the degree of drought stress and time.Furthermore,the contents of soluble protein and proline in Dongnong 425 were higher than those in Songjing 6,and the resilience and the resistance was also the same.4.The protein content of grain in Dongnong 425 was significantly increased under drought stress at booting stage,and the rise decreased with more serious of drought degree;The total grain protein contents of Songjing 6 were mild> moderate> control> severe(except for 7 d after heading,severe drought was more than control).And the rise of Dongnong 425 more than that of Songjing 6.The overall performance of Songjing 6 grain albumin showed moderate> mild> control> severe drought,while Dongnong 425 increased with the degree of drought.,the globulin and gliadin protein of Songjing 6 and Dongnong 425 showed moderate> mild> severe drought> control.Dongnong 425 gliadin and glutelin protein content showed moderate> severe> mild> control,while Songjing 6 showed mild> moderate> severe> control.And each component of Dongnong 425 is higher than that of Songjing 6.5.The yield of Japonica rice in cold-region decreased under drought stress at booting stage,and with the decrease of soil water potential,the decline increased,and the difference between varieties was significant.Compared with Songjing 6,Dongnong 425 had a less decline in yield.Due to the decrease of number of grains per spike,seed setting rate,and 1000-grain weight,yield significant decreased. |
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