Agricultural Water Management (Oct 2024)
Compound extreme heat and drought stress alter the spatial gradients of protein and starch in wheat grains
Abstract
The spatial gradients of protein and starch in wheat grains affected the grain milling characteristics and flour utilization. The increase in compound heat stress and drought stress (HDS) due to global climate change threatens wheat grain yield and quality parameters, but the impacts of extreme climate events on the gradients of protein and starch in wheat grains remain unclear. In this study, two-year, environment-controlled experiments with four heat stress levels (17/27, 21/31, 25/35, and 29/39°C) and three drought stress levels (30 %, 55 %, and 75 % field capacity) were conducted to investigate the effects of HDS on the gradients of protein and starch concentrations within the five grain layers. The results showed that HDS resulted in significantly greater protein concentrations, while resulting in lower starch concentrations in the wheat grain layers. Among the five layers, the endosperm layers exhibited the greatest increase in protein concentration under HDS, but the starch concentration under HDS decreased in the order of husk > aleurone > endosperm layer. HDS unevenly altered the protein and starch concentrations of the five grain layers. There was significant linear relationship between relative protein and starch concentration with accumulated heat degree days (AHDD). With a 1°C·d increase in AHDD, the protein concentration in the five grain layers increased by 1.17–2.19 %, while the starch concentration decreased by 0.62–0.90 %, depending on the drought stress levels. A significant linear relationship was also observed between the relative protein and starch concentrations and evapotranspiration (ET). A 1 mm increase in ET led to a protein concentration decrease of 0.58–0.76 % in P1-P5, with a corresponding starch concentration increase of 0.28–0.46 %, depending on cultivar and treatment stages. Our results indicate that HDS significantly impacts the grain quality parameters for the flour milling process and human diet and will provide important insights into adapting wheat quality to climate change.
