Abstract
Based on the theory of ecological crop nutrient deficiency and compensation effect, the nitrogen (N) deficiency at tillering stage and N compensation at young panicle differentiation stage in rice (Oryza sativa L.) was selected to study. Four N treatments were treated, and the effects of N deficiency and compensation were investigated on grain yield, N uptake and utilization and the physiological characteristics of rice. The results showed that the yield per plant presented an equivalent compensatory effect. Double N compensation led to superiority in the number of effective panicle per plant, increased the activity of nitrate reductase and glutamine synthetase. The content of endogenous growth-inhibitory hormone abscisic acid (ABA) decreased in the leaves, photosynthesis was enhanced, and the number of tillers per plant increased after double N compensation. During maturation stage, the panicle dry weigh in T1 (double N compensation at young panicle differentiation stage, after N deficiency at tillering stage) was higher than that in CK1 (constant supply of N throughout different stages of growth) and the biomass per plant in T1 increased by 1.47% compared with CK1. N contents in all organs, N accumulation, and total N content were all higher in T1 during maturation stage. Moreover, N agronomic efficiency, N physiological efficiency, and N partial factor productivity were optimized for T1 and CK2 (constant N compensation at young panicle differentiation stage, after N deficiency at tillering stage) compared with CK1. This study contributes to the understanding of the physiological mechanisms underlying the compensation of N deficiency in rice.
Highlights
To cope with growing population and limited land resources, improving rice (Oryza sativa L.) varieties to increase yield per unit area has become the consensus goal of global rice research
CK0, N fertilizer was not supplied during all stages of growth; CK1, constant supply of N throughout different stages of growth; CK2, constant N compensation at young panicle differentiation stage, after N deficiency at tillering stage; T1, double N compensation at young panicle differentiation stage, after N deficiency at tillering stage
Compared with CK1, the 1000-grain weight in CK2 and T1 had increased by 2.81 and 1.05%, respectively. These results indicated that for this double-cropping super hybrid late rice, double N compensation after N deficiency would rendere visible compensation in terms of yield per plant, effective panicle per plant and harvest index (HI)
Summary
To cope with growing population and limited land resources, improving rice (Oryza sativa L.) varieties to increase yield per unit area has become the consensus goal of global rice research. The super rice varieties have morphological characteristics such as moderate tillering, straight flag leaves, above average short height, firm stems with lodging resistance, and large panicles with more spikelets These varieties exhibit superior physiological functions such as high photosynthetic efficiency, strong root activity, and coordination of “source-sink-stream.”. The cultivation area has a size of more than eight million hectares per year, and especially the super hybrid rice achieves remarkable results in the double-cropping paddy fields of southern China (Wu et al, 2016). These varieties increase both production and income, promote the renewal of rice cultivars, and significantly improve the capacity of material production and yield potential. It is worth to gain in-depth understanding about the formation of the N deficiency compensation effect and the underlying physiological mechanisms, as well as the changes in N uptake and utilization
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