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University of Western Sydney (2019)

Investigating the main and interactive effects of vapour pressure deficit, soil water deficit, warmer temperatures and elevated CO2 on cotton growth and physiology

Theerasutthikul, Potjanee

Titre : Investigating the main and interactive effects of vapour pressure deficit, soil water deficit, warmer temperatures and elevated CO2 on cotton growth and physiology

Auteur : Theerasutthikul, Potjanee

Université de soutenance : University of Western Sydney

Grade : Master of Research 2019

Résumé partiel
Climate change factors such as rising temperature, atmospheric carbon dioxide concentration [CO2] and increased drought frequency and intensity have been shown to affect cotton physiology and productivity. To investigate the effect of climate change on cotton, we divided our study into two parts, of which the first study focused on the effect of vapour pressure deficit (VPD) and soil water deficit (SWD) on stomatal response and the second study focused on the effect of increased temperature (TE) and elevated [CO2] (CE) on cotton growth and physiology. We conducted both experiments in an environmentally controlled glasshouse to imitate the projected drier, warmer and increased [CO2] conditions. Our goal was to use cotton to improve the understanding of the physiological and growth response of C3 crops to changing climate.

The first experiment was developed as climate change has driven increasing air temperature and longer warm seasons throughout Australia. These changes have resulted in a drier atmosphere (higher vapour pressure deficit, VPD) and drier soil (high soil water deficit, SWD) that contributes to cotton stress and therefore, reduces cotton growth and physiological performance. This study investigated the effect of atmospheric and soil drought on cotton physiology by experimentally controlling air temperature (22, 26, 30 and 34C), humidity, and soil moisture content (100% and 50% field capacity) to determine the physiological responses of cotton to these factors individually, and in combination. A novel approach in this study was to assess the two components (temperature and relative humidity) of VPD to examine the relative contribution of each factor to plant response to VPD, and to determine whether SWD affected this relationship. Higher SWD decreased stomatal conductance (gs), and higher VPD further reduced gs. Higher SWD and VPD also reduced transpiration (E), but to a lesser degree than the reduction in gs. In contrast, photosynthesis (A) was not affected by the change in SWD, nor very responsive to VPD or temperature. The stomatal model predicted that well-watered cotton would increase whole-plant water use more than cotton grown in SWD under elevated temperature. Présentation

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