Effect of vapour pressure deficit on gas exchange of field-grown cotton

Authors: BROUGHTON, KATRINA - Commonwealth Scientific And Industrial Research Organisation (CSIRO); Payton, Paxton; TAN, DANIEL - University Of Sydney; TISSUE, DAVID - Western Sydney University; BANGE, MICHAEL - Cotton Seed Distributors

Submitted to: Journal of Cotton Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/18/2021
Publication Date: N/A
Citation: N/A

Interpretive Summary: Vapor pressure deficit is a term that essentially describes the difference between water content of the atmosphere and its saturation point, that is the maximum amount of water air can hold at a given temperature. This pressure difference (VPD) is an important term when describing the driving force of water from plants to the atmosphere. Understanding VPD responses is critical to managing crop production and predicting crop responses over a range of climates. With projected warmer air temperatures, changes in rainfall distribution and altered VPD in future climates, it is important to understand the potential effect of VPD on leaf-level physiology of field-grown crops. In this study, scientists in Lubbock, Texas and collaborators in Australia examined cotton response to changing VPD in the field by manipulating key environmental parameters and found that VPD was a major contributor to water use and plant response over a wide range of growth conditions. This study highlights the importance of accounting for VPD in climate change research, given that plants are highly responsive to changes in VPD. This experiment provides a basis for physiology and production models, particularly in terms of cotton response to projected climatic environments and can be incorporated into models to more accurately predict cotton water use in the field.

Technical Abstract: The aim of this study was to assess the impact of altered VPD on leaf-level physiology of field-grown cotton to improve current understanding of the plant-by-environment interaction, thereby contributing to validation and improvement of physiological and yield response models. Different VPD environments in the field were generated by planting cotton on three dates within the sowing window (early-season (S1) = 5 th October 2011; mid-season (S2) = 9 th November 2011; and late-season (S3) = 30 th November 2011). VPD was also modified by altering crop irrigations. Results: VPD accounted for the largest proportion of the explained variation in both stomatal conductance (32~39%) and photosynthetic (16~29%) responses of cotton. Generally, smaller percentages of variation were attributed to other main factors such as the individual plant (Plant), and accumulated temperature stress hours (ASH; a measure of plant water status over time) and interactive factors, including leaf vapour pressure deficit (VPD L ) x Plant and Plant x ASH; however, a proportion of variation was unexplained. In addition, the A sat / E (instantaneous transpiration efficiency; (ITE) model developed based on cotton grown in the glasshouse was applied to cotton grown in the field. We found that the modelled A sat / E and field-measured A sat / E were very similar, suggesting that the mechanistic basis for ITE was similar in both environments.