Prolonged drought affects the interaction of carbon and nitrogen metabolism in root and shoot of cotton

Abstract

Maintaining assimilates metabolism is critical for root and shoot normal function, especially during drought. However, little is known about how plants coordinate assimilates transport and internal root and shoot assimilates usage under drought. To test these objectives, a greenhouse experiment was carried out in which two cotton cultivars (Dexiamian 1 and Yuzaomian 9110) with varied drought tolerance were subjected to a continuous soil water deficit. We used stable-isotope labeling to examine the changes in assimilates allocation, as well as the responses of metabolic activities in the root and leaf to drought. According to the findings, root nitrogen absorption was reduced as a result of insufficient ATP supply and the down-regulated GhNPF4.6 . Further, the limited root nitrate absorption and nitrate transport from root to shoot reduced leaf nitrogen accumulation. Moreover, less proportion of nitrogen invested in photosynthetic apparatus under drought limited the leaf photosynthetic performance. Drought suppressed leaf CO 2 fixation and photosynthates export, but the relative amount of photosynthates allocated in root increased due to the increasing expression of sucrose transporters. However, the stunted respiratory metabolism limited root function although the carbohydrates were sufficient. We conclude that drought disrupts assimilate partition between root and shoot, restricts root carbohydrates use, and reduces leaf photosynthetic nitrogen utilization, resulting in a functional imbalance between root and shoot. • Drought limited CO 2 fixation and promoted photoassimilates transport to root. • Root respiratory metabolism was inhibited by drought. • The inadequate energy supply and the down-regulated GhNPF4.6 reduced nitrate uptake. • The limited leaf photosynthetic nitrogen utilization intensified photosynthesis loss.