Effect of Nitrogen Fertilizer Topdressing for Panicle Differentiation on Grain Filling of Hybrid indica Rice and Its Relationship with the Activities of Key Enzymes for Starch Synthesis
[Objective]To elucidate the impact of nitrogen panicle fertilizer on the key enzymes involved in grain filling and starch synthesis in hybrid rice.[Methods]Two hybrid rice varieties,Jinyou 1319(high amylose)and Rongyou 702(low amylose),characterized by substantial differences in amylose content,were chosen for a study examining the effects of the levels of nitrogen fertilizer topdressing for panicle differentiation on the activities of key enzymes in grain filling and starch synthesis.Various nitrogen topdressing treatments were applied,representing four pure nitrogen levels(0,60,90,and 120 kg/hm2 denoted as CK,N1,N2,and N3,respectively).[Results]Grain filling characteristics of hybrid rice exhibited significant variations under different nitrogen fertilizer topdressing treatments,with diverse performances observed among different varieties.The application of nitrogen fertilizer topdressing notably decreased the amylose content of rice.Both Gmax and Gmean of Jinyou 1319 exhibited a trend of N2＞CK＞N1＞N3 under different nitrogen fertilizer topdressing levels,while those of Rongyou 702 followed a tendency of N3＞N2＞CK＞N1.The nitrogen fertilizer topdressing significantly increased the activities of ADPG and DBE in grains at 5-25 days after anthesis,reduced the activities of GBSS in grains at 5-15 days after anthesis,and decreased the activities of SSS and SBE in grains at 5-25 days after anthesis.[Conclusion]The optimal application rate of nitrogen fertilizer topdressing for panicle differentiation was lower for the high-amylose variety Jinyou 1319 compared to the low-amylose variety Rongyou 702:the optimal rate of nitrogen fertilizer topdressing for Jinyou 1319 was 90 kg/hm2,and for Rongyou 702,it was 120 kg/hm2.The nitrogen fertilizer topdressing significantly reduced the activities of GBSS and SSS,accompanied by a decrease in SBE activity and an increase in DBE activity,ultimately leading to a reduction in rice amylose content.Seed ADPG activity did not significantly affect rice amylose content in this study.
ricenitrogen fertilizer topdressing for panicle differentiationgrain fillingstarch synthesis
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