Response of 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: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 11/4/2021
Publication Date: N/A
Citation: N/A

Interpretive Summary: Chlorophyll pigments are important for plant photosynthesis for production of photosynthates. This work showed that leaf chlorophyll content can be used to identify high heat and low-soil water adapted cotton for breeding improvement. This work has also identified that more work is needed to understand the source/sink relationship of photosynthates between leaf chlorophyll content and developing bolls.

Technical Abstract: Chlorophyll is the primary light harvesting pigment located in the chloroplast and is responsible for driving photosynthesis for production of photosynthates. Reduced chlorophyll content will limit the energy available for photosynthesis which will reduce plant growth and development. If plants produce too much chlorophyll, more light energy will be adsorbed than can effectively be used for photosynthate production and may be harmful. Heat stress has long been identified as a significant factor reducing leaf chlorophyll content. Previous studies in cotton found reduced chlorophyll content was associated with reduced height and photosynthesis parameters However, the duration and intensity of heat stress was not studied, nor were the effects on lint yield other yield components. To avoid heat stress, cotton plants will maintain stomatal conductance and transpiration rates for evaporative cooling. However, evaporative cooling can have adverse effects by depleting soil water in the root zone, which could lead to severe water deficit without supplemental irrigation. Understanding how high heat and low soil-water affect chlorophyll content and yield components can identify opportunities for breeding improvement; therefore, a multi-year trial with four irrigation treatments and two planting dates was conducted in Maricopa Arizona. The results showed that low-soil water significantly increased leaf chlorophyll content while high heat significantly reduced content. Structured equation modeling revealed 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. The findings in this study supports the use of leaf chlorophyll to identify high heat and low-soil water adaptive cotton germplasm for future sustainable cotton production. The study also identified that more work is needed to understand the source/sink relationship of photosynthates between leaf chlorophyll content and developing bolls.