Regulatory effects of organic compound L-glutamic acid on multi-scale structural characteristics of starch in...

Post-anthesis drought impairs wheat starch synthesis, compromising structure and function. Organic compounds are widely used to modulate crop growth and mitigate environmental stressors, but the potential of L-glutamic acid (L-Glu) in alleviating drought-induced effects on starch biosynthesis and structural attributes remains unexplored. A two-year field trial (2022-2024) revealed that: (1) Foliar application of L-Glu significantly increased the contents of amylopectin, amylose, and total starch in drought-stressed grains, increased the volumetric proportions of B-type and C-type starch granules, and reduced the number of surface and internal micropores and microchannels within starch granules. (2) L-Glu enhanced drought-tolerant wheat's starch branching level and the proportions of A- and B₁-chains, inducing structural reorganization evidenced by increased relative crystallinity, increased Fourier-transform infrared peak intensity ratios (1047/1022 cm^-1 and 1022/995 cm^-1), and reduced Raman full width at half maximum (FWHM) at 480 cm^-1, synergistically optimizing short- and long-range molecular order. (3) L-Glu improved starch transparency, wholemeal swelling power, and modified thermal stability and pasting properties, enhancing starch quality for food and industrial applications. In summary, under post-anthesis drought stress, the organic compound L-Glu enhanced starch biosynthesis in wheat grains and effectively alleviated the negative impacts of drought on starch quality through multiscale structural optimization, thereby improving its functional properties.