Effects Of Chlorophyll Degradation On Material Transport And Yield In Rice Grain Filling

The accumulation of dry matter in rice mainly comes from the photosynthetic products of leaves,and leaf senescence is one of the key factors affecting the photosynthesis capacity of rice.Therefore,it is of great significance to study the effects of leaf senescence on leaf photosynthesis,biomass partitioning and its physiological mechanisms to achieve high yielding and green production of rice.In this study,japonica rice wuyunying7?NYC3 over expressed lines NYC3-OX1?NYC3-OX2?NYC3-OX3?NYC3-OX4,NYC3 inhibited lines NYC3-RNAi1?NYC3-RNAi2?NYC3-RNAi3 were used as materials.There were several treatments,including control,spray of Abscisic acid?ABA?,spray of 6-Benzylaminopurine?6-BA?,spray of Ethylene?ETH?,spray of Aminoethoxyvinylglycine?AVG?,and alternate wetting and moderate soil drying irrigation?AWMD?.Based on these data,we studied the effects of NYC3,hormone,water irrigation on photosynthesis,partitioning,plant growth and development,yield and yield components on rice cultivar wuyunjing7.We want to elucidate the effects of leaf aging on biomass partitioning and its physiological mechanisms.The main results are as follows:1.Yields and agronomic traitsThe yields of NYC3 over expressed lines NYC3-OX1?NYC3-OX2?NYC3-OX3?NYC3-OX4 were 7.50,7.47,7.93,8.18 t hm^-2,respectively,and were 4.31%,3.89%,10.29%,17.94%higher than the wild type wuyunjing7.The yields of lines NYC3-RNAi1?NYC3-RNAi2?NYC3-RNAi3 were 6.79,6.73,7.15t hm^-2,respectively,and were 5.56%,6.40%,0.56%lower than the wild type wuyunjing7.The higher spikelet number is the main reason of higher yield in line NYC3,The yields of treatment ABA,6-BA,AVG and AWMD were 7.60,7.22,7.24,and 7.78 t hm^-2,respectively,and were 5.70%,0.42%,0.70%,and 8.20%higher than wild type.The yield of treatment ETH was 7.04 t hm^-2,which was 2.09%lower than the wild type.The average yield of over expression line?i.e.NYC3-OX1,NYC3-OX2,NYC3-OX3,and NYC3-OX4?under ABA treatment and AWMD were 7.94,and 7.97 t hm^-2,respective,and were 2.19%and 2.57%higher than control.The average yield of over expression line under ETH treatment was 7.56 t hm^-2,,which was 2.73%lower than control.While the yield was not significantly affected under 6-BA and AVG treatment.The average yield of lines NYC3-RNAi1?NYC3-RNAi2?NYC3-RNAi3 under ABA treatment and AWMD were 7.08,and 7.12 t hm^-2,respectively,and were 2.76%and 3.34%higher than control.The average yield of over expressed lines under ETH treatment was 6.74 t hm^-2,,which was 2.16%lower than the control.While the yield were not significantly affected by 6-BA and AVG treatment.The main reasons for the increase yields of ABA treatment and WMD treatment were the significant increase of seed setting rate and 1000-seed weight.Compared with control,the number of tillers of over expressed lines NYC3-OX1,NYC3-OX2,NYC3-OX3,NYC3-OX4 were all increased,while the lines NYC3-RNAi1,NYC3-RNAi2,NYC3-RNAi3 were decreased.ABA,6-BA,AVG and AWMD treatment all increased the tiller number,among which ABA and WMD increased more significant,while ETH decreased the tiller number.The results showed that the tiller number of rice could be improved by gene regulation,hormone regulation and water regulation.2.Photosynthetic characteristicsThe leave color of NYC3 over expressed lines NYC3-OX1,NYC3-OX2,NYC3-OX3,NYC3-OX4 were yellower than control,and the chlorophyll content and nitrogen content were lower than control.While the leaf color of NYC3 inhibited lines NYC3-RNAil,NYC3-RNAi2,NYC3-RNAi3 were greener,and the chlorophyll content and nitrogen content were also higher than control.The content of psbD protein of NYC3 over expressed lines was lower than control,while the Rubisco enzyme content was higher control.The psbD protein content and Rubisco enzyme content of NYC3 inhibited lines were higher than control.However,there was no significant difference in photosynthetic rate between NYC3 over expressed lines and control.Compared with the control,ABA and ETH treatment reduced the chlorophyll content and nitrogen content,6-BA and AVG treatment kept the chlorophyll content and nitrogen content at a higher level,AWMD treatment reduced the chlorophyll content in the early and middle growth stage,and maintained a higher level in the later growth stage.ABA and ETH treaement significantly reduced the content of psbD protein,while 6-BA,AVG and AWMD increased the content of psbD protein.The content of Rubisco enzyme in all treatment was higher than that in control.This indicated that over expression of NYC3 gene,ABA and AWMD treatment could promote the decrease of chlorophyll in leaves,but did not significantly affect the photosynthesis.3.Transport characteristicsNYC3 over expressed lines NYC3-OX1,NYC3-OX2,NYC3-OX3,NYC3-OX4 accumulated more non-structural carbohydrates?NSC?,translocate more NSC to grains,and the grain filling rate was also improved.The activity of combination state of starch synthase?GBSS?,ADP glucose coke phosphorylase?ADPG?,starch branching enzyme?SBE?has increased significantly,while the opposite results were observed in NYC3 inhibited lines NYC3-RNAil,NYC3-RNAi2,and NYC3-RNAi3ABA,6-BA,AVG and AWMD treatment improved translocation amount of NSC,transportation rate and contributed more to grain yield,improved the grain filling rate and the activity of GBSS,SBE,AGP,among which ABA and AWMD treatment was more significant,while the opposite was found in ETH treatment.The results showed that ABA and AWMD treatment promoted the transport of carbohydrate to grains and improved the transport efficiency.The results were consistent with the distribution of 13C in stem,leaf and grain.The results showed that chlorophyll degradation was beneficial to the transport of dry matter and increased yield.Exogenous hormones,such as ABA and AWMD treatment were conducive to degrade chlorophyll,age prematurely in time,increase the transport of dry matter to grains,and increase yield.