Response of upland cotton (Gossypium hirsutum L.) leaf chlorophyll content to high heat and low-soil water in the Arizona low desert

Authors: Thompson, Alison; Conley, Matthew; Herritt, Matthew; Thorp, Kelly

Submitted to: Photosynthetica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/2/2022
Publication Date: 4/13/2022
Citation: Thompson, A.L., Conley, M.M., Herritt, M.T., Thorp, K.R. 2022. Response of upland cotton (Gossypium hirsutum L.) leaf chlorophyll content to high heat and low-soil water in the Arizona low desert. Photosynthetica. 60(2):280-292.
DOI: https://doi.org/10.32615/ps.2022.014

Interpretive Summary: The unique environment at the Maricopa Agriculture Center provided the opportunity to measure crop growth and development under fluctuating high temperatures and variable soil-water content. The resulting data revealed that light absorption efficiency and evaporative cooling regulation could lead to improved cotton adaptation for sustainable production in a changing environment. The data also highlight the importance of utilizing crop management strategies, including irrigation and nitrogen management. Novel genotype × environment × management studies are needed for effective plant breeding in a changing environment.

Technical Abstract: Cotton is an economically important crop supporting a global industry. Like many crops, abiotic stress, including high heat and low-soil water content, threaten the future of sustainable cotton production. Both high heat and low-soil water can reduce net photosynthesis resulting in low fiber yields. Leaf chlorophyll content has a direct relationship with photosynthetic rate. Understanding how high heat and low soil-water affect chlorophyll content can identify opportunities for breeding improvement that will lead to sustainable fiber yields under adverse conditions. A multi-year trial located in Maricopa Arizona included four irrigation treatments, two planting dates, and eight upland cotton entries. Measurements included leaf chlorophyll content, available soil water, ambient air temperatures, and cotton growth measurements collected by a high clearance tractor equipped with proximal sensors. Structured equation modeling showed that low-soil water significantly increased leaf chlorophyll content while high heat significantly reduced content. The results also indicated that during periods of high heat, cotton will divert available resources to leaf area and chlorophyll content and that cottonseed are a stronger sink for available resources than the fiber. Identification of cotton germplasm that are light absorption efficient and that maintain leaf chlorophyll content could improve cotton production in hot, dry environments. Further research is needed to understand the source/sink relationship of photosynthates between leaf chlorophyll content and developing bolls.