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Effects of nitrogen fertilizer applications on the early senescence and grain filling characteristics of Tartary buckwheat

Yu Zhang^?, Peiyun He^?, Shihong Li, Yan Chen, Xinhui Wu, Kaifeng Huang^*, Xiaoyan Huang^*

 
ABSTRACT:     This study used four different nitrogen fertilizer applications to determine their effects on early senescence and grain filling of the Tartary buckwheat “cv Jinqiao 2”. Changes in grain filling dynamics, starch synthesis enzyme activity, photosynthetic characteristics, antioxidant enzyme activity, malondialdehyde content, agronomic traits, and yield formation were assessed. The shape parameters (N values) were all lower than 1 for the four applications. Initial growth power (R₀) and maximum grain filling rate (Gmax) were the highest for the middle nitrogen fertilizer application (MN) treatment. The middle filling stage had the largest contribution rate to grain weight, followed by the later filling stage; and the smallest contribution was noted in the early filling stage. The activity of starch synthase initially increased but eventually decreased with the growth period. In addition, the activity of starch synthase was strong under MN and high nitrogen fertilizer application (HN) treatment. Under MN, the net photosynthetic rate, stomatal conductivity, and transpiration rate of JQ2 leaves were high, and the superoxide dismutase, peroxidase, and catalase activities were strong. Moreover, malondialdehyde content was the lowest. The grain number per plant, grain weight per plant, 1000-grain weight, and yield were higher in MN than in the other three treatments. In summary, the suitable nitrogen fertilizer treatment (MN) can enhance the photosynthetic efficiency, promote Tartary buckwheat grain filling, delay premature senescence, and increase the grain weight and final yield.

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* Corresponding author, E-mail: hkf1979@163.com, huangxy666@126.com

Received 20 Feb 2021, Accepted 25 May 2021