Conclusions
The current study examined the effects of growth temperature, water deficit and heatwave on leaf carbon gain and biomass production in cotton plants. Warmer growth temperature promoted growth rate and leaf level carbon gain due to greater stomatal conductance and thermal acclimation of photosynthesis, but compromised aboveground dry mass production. Furthermore, growth temperature affected the response of leaf carbon gain and/or yield to nocturnal warming and heat stress. Water stress also exerted control over carbon gain and reproductive dry matter, either independently or interactively, but these effects were less pronounced. The instantaneous impacts of the heatwave on carbon gain and biomass production was largely neutralized, yet fruit biomass was negatively affected.
Overall, temperature appears to be a major determinant of biomass production in cotton. More specifically, both short- and long-term increases in daytime temperature will lead to reduced cotton yields, while nocturnal warming has limited capacity to alter that impact. Additionally, yield will not be strongly diminished if soil water content is maintained well above the level triggering leaf wilting. Therefore, plant traits enabling heat tolerance especially for heatwave conditions should continually be targeted and prioritized in future breeding selection. This study adds to the current knowledge about the impacts of global climate change on cotton by providing evidence of the response of carbon gain and biomass to some of the key climate change factors, and highlights the interactive effects of environmental factors on plant growth. Subsequent studies in the field are required to more fully uncover the mechanisms that can be used to model crop yield under future climates.
Conflict of interest: The authors declare that they have no conflict of interest.