Sink-source unbalance leads to abnormal partitioning of biomass and nitrogen in rice under extreme heat stress: An experimental and modeling study

Abstract

Extreme heat stress occurred frequently with increasing global warming, and significantly reduced crop yield. Experimental and modelling studies for grain yield formation under heat stress were widely carried out, but carbohydrate and nitrogen re-distribution caused by unbalanced sink-source relationships have rarely been noticed. The multi-year experimental datasets involving different heat stress intensities, durations, and rice varieties showed that rice stem was re-activated as a sink organ during grain filling stage after short-term extreme heat stress at flowering, where a large amount of carbohydrate and nitrogen accumulated. The stems may become alternative harvest organs under climate change, whereas needs accurate assessments for adaptation strategy. We further improved the simulation of biomass and nitrogen accumulation in different rice organs according to the re-evaluated sink-source relationship under heat stress, based on RiceGrow model. The nitrogen filling process in stems after the termination of grain filling was quantified, and the delay of leaf senescence was also simulated by accounting for the leaf nitrogen distribution within the canopy under heat stress. The improved model explained the cause and effect of unusual carbohydrate and nitrogen accumulation under heat stress in rice, and can be a useful tool for adaptation strategy under climate change.