Abstract
Rice (Oryza sativa L.) is an important crop in China. Although it is known that its yield is restricted by nitrogen (N) supply, the response of the root system to N supply specifically has not been systematically explored. This study aimed to investigate the effect of N uptake on grain yield to clarify the relationships between root morphophysiological traits and N uptake, and to understand relation between phytohormones and root morphophysiological traits. Two N-efficient absorption cultivars (NEAs) and two N-inefficient absorption cultivars (NIAs) were grown in the field, and three N conditions, deficient N (60 kg ha–1), intermediate N (180 kg ha–1), and sufficient N (240 kg ha–1), were applied during the growing season. The results showed higher dry matter and grain yield in NEAs than in NIAs, which was mainly attributed to increased N uptake in the mid- and late growth stages under all N conditions. And NEAs have different root regulation methods to obtain higher N accumulation and yield under different N supply conditions. Under lower N conditions, compared with NIAs, NEAs shown greater total root length, root oxidation activity, and root active absorbing surface area and smaller root diameter owing to higher indole-3-acetic acid and cytokinin content and lower 1-aminocyclopropane-1-carboxylic acid content in the early growth stages to respond to low N stress faster, laying a morphophysiological basis for its high N-uptake capacity in the mid- and late growth stages. Under higher N conditions, NEAs had higher root oxidation activity and root active absorbing surface area for N uptake and yield formation owing to higher abscisic acid and cytokinin content in the mid- and late growth stages, which improved the seed setting rate, thereby increasing the rice grain yield. These results suggest that NEAs can optimize the morphophysiological characteristics of roots through phytohormone regulation to adapt to different nutrient conditions, thereby promoting N accumulation and yield formation in rice.
Highlights
Rice (Oryza sativa L.) is one of the world’s most important crops, with rice the staple food for more than half of the world’s population (Hua et al, 2015; Zhang et al, 2019)
The seed setting rate decreased with increasing N rate in all cultivars, which was significantly higher for N-efficient absorption cultivars (NEAs) than for N-inefficient absorption cultivars (NIAs) under intermediate and sufficient N conditions, implying that a higher grain yield (GY) for NEAs under intermediate and sufficient N conditions was mainly attributed to a higher seed setting rate
N accumulation in the maturity stage under three N conditions was used as the evaluation index to analyze two NEAs and two NIAs, which were used to study the effect of N uptake on grain yield, in order to clarify the relationship between root morphophysiological traits and N uptake, and to understand relation between phytohormones and root morphophysiological traits
Summary
Rice (Oryza sativa L.) is one of the world’s most important crops, with rice the staple food for more than half of the world’s population (Hua et al, 2015; Zhang et al, 2019). Increasing rice yield can crucially contribute to global food security. Nitrogen (N) is the most essential nutrient in rice production, and current high yields of rice are associated with the application of large amounts of N fertilizer (Xu et al, 2012). The use of N fertilizer for rice production in China accounts for 37% of the global total (Li et al, 2014). N supply drives productivity, the N use efficiency (NUE) in the current rice production system is low despite high N fertilizer input, which is the main factor limiting rice yield (Peng et al, 2006). Current research focuses on ways to synergistically improve the NUE of rice while increasing rice yield
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