Drought response modeling of leaf photosynthetic parameters in two Gossypium species

Authors: Chastain, Daryl; SNIDER, JOHN - University Of Georgia; SINGH, BHUPINDER - Texas A&M Agrilife; VIRK, GURPREET - University Of Georgia

Submitted to: Journal of Agronomy and Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/27/2024
Publication Date: 4/30/2024
Citation: Chastain, D.R., Snider, J., Singh, B., Virk, G. 2024. Drought response modeling of leaf photosynthetic parameters in two Gossypium species. Journal of Agronomy and Crop Science. 210(3):12709. https://doi.org/10.1111/jac.12709.
DOI: https://doi.org/10.1111/jac.12709

Interpretive Summary: Cotton is well adapted to dry areas, but drought can lead to fiber yield loss. The mechanisms leading to the declines in photosynthesis are primarily explained by decreases in carbon dioxide inside the leaf; however, there is still considerable debate around the light harvesting processes. To fill in these knowledge gaps, we designed a study to investigate the effect of drought on leaf level metabolism from the point of light harvesting to actual carbon fixation in pima and upland cotton. We found that in both species CO2 diffusion is the primary limitation under drought. Interestingly, while upland cotton dissipates excess energy through photorespiration, pima cotton uses other mechanisms such as heat dissipation. This information can be useful to modelers when attempting to predict crop responses to future climate scenarios.

Technical Abstract: Cotton is well adapted to dry areas, but progressive water deficits can lead to decline in net photosynthesis (A), ultimately reducing yield. However, the exact mechanism responsible for this decline in net photosynthesis (stomatal or non-stomatal) is not fully understood under field conditions, partially due to limitations in the ability to collect critical data. To this end, a field study was conducted to quantify the impact of progressive mild drought, as measured by midday stomatal conductance to water vapor (gs), on cotton leaf metabolism in pima and upland cotton. Survey gas exchange and rapid photosynthetic CO2 response (RACiR), were conducted during flowering on the same leaf. The study observed decline in A as gs declined for both species. Correlation analysis indicated typical relationships with A and parameters associated with stomatal limitations (Ci, Cc, gs, E); however, it was found that while pima exhibited a strong relationship between Jmax and ETR, upland cotton did not. Furthermore, when ETR is broken down into proportions contributing to net photosynthesis and photorespiration (ETRA, ETRP, respectively), we found that a greater proportion of ETR is being shuttled to the photorespiratory pathway in upland, relative to pima as gs decreases.