Supplemental red light improves wheat stem quality by regulating cell wall components and structure

1. Supplemental light quality significantly affected stem components compared to natural light. 2. Red light enhances the syringyl and guaiacyl dominated cross-linking structure in lignin. 3. Enhanced cellulose and lignin structure of stems is the key to increased breaking strength. Lodging restricts the further increase of wheat yield. In dense planting environments, there is a contradiction between the weakening of light signals at the base of the population and the need for strengthened stem quality. However, there is currently insufficient quantitative and qualitative information on how light quality affects the content and structure of stem cell wall components. This study used Shannong 16 (SN16) and Shannong 23 (SN23) as experimental materials and set up red light (R) and far-red light (FR) treatments, with natural light (CK) as the control, to explore the effect of light quality on stem cell wall components. The results showed that light quality treatments induced significant phenotypic and cell wall component and structural changes in plants. Specifically, R treatment significantly increased the cellulose crystallinity and lignin precursors in the stem and promoted the increase of cellulose and lignin levels. In particular, changes in lignin composition (increased S and G subunits, decreased H subunits) and increased dimers and trimers composed of G and S were more substantial than the changes. This phenomenon indicates that the R treatment enhanced stem mechanical strength by increasing cellulose crystallinity and lignin cross-linking structure in the cell wall. In summary, as a cultivation measure aimed at reducing lodging in the field by improving the light quality at the base of plants, this strategy has the potential to enhance stem lodging resistance and increase yield in future dense wheat plantings.