Stomatal closure response of maize to soil drying at different vapor pressure deficit conditions and the role of abscisic acid

Authors: MURA, JYOSTNA - Orise Fellow; Reddy, Vangimalla

Submitted to: Plant Physiology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/9/2020
Publication Date: 7/13/2020
Citation: Mura, J., Reddy, V. 2020. Stomatal closure response of maize to soil drying at different vapor pressure deficit conditions and the role of abscisic acid. Plant Physiology and Biochemistry. 154:714-722. https://doi.org/10.1016/j.plaphy.2020.07.023.
DOI: https://doi.org/10.1016/j.plaphy.2020.07.023

Interpretive Summary: Adverse climatic conditions such as drought and high evaporative demand (dry atmosphere) are the predominant cause of low maize yields worldwide. Development of maize hybrids which can conserve water under both water-limited and dry environments is the key to reduce crop yield loss. In this study, physiological and biochemical responses of maize were studied by subjecting plants to drought under three different climate conditions (humid to dry). We report that the plant hormone (abscisic acid) and two genes involved in water transport are responsible for conserving the water in maize under drought by closing stomata. Findings in the study are useful in understanding the drought response mechanisms in maize and to utilize the information in breeding programs to develop drought-tolerant varieties.

Technical Abstract: A plant transpiration rate under progressive soil drying conditions remains constant until a threshold soil-water content is reached, and thereafter, it declines linearly. Plant hydraulic conductivity is probably to be involved in determining the threshold values where water supply is limiting. In maize, a decline in plant transpiration has been observed within a range of threshold values of fraction transpirable soil water (FTSW) which was usually 0.3 -0.4. However, the stability of this function and the involvement of abscisic acid (ABA) and water channel proteins in such responses have not been compared at various levels of atmospheric evaporative demand conditions. It was hypothesized that high evaporative demand resulting in high plants transpiration might influence the threshold value of FTSW under drought stress. This study was conducted in controlled environment chambers with a maize hybrid (Pioneer hybrid 34N43) imposing progressive drought stress under three levels of vapor pressure deficit (VPD- 1.2, 2.3 and 3.5 kPa) conditions. In this study, a shift in the threshold FTSW from VPD 1.2 kPa (FTSW- 0.42) to 3.5 kPa (FTSW- 0.51) was observed, showing an effect of evaporative demand on stomatal closure response under soil drought conditions. Foliar ABA measured at three different intervals of the experiment showed a significant maximum increase about the same time as of stomatal closure initiated (FTSW-threshold), indicating ABA involvement. An increase in the tonoplast intrinsic protein (TIP) and plasma membrane intrinsic protein (PIP) expression levels were observed as the drought progressed. Overall, this study suggests the influence of evaporative demand on the initiation of stomatal closure of drought-tolerant maize subjected to soil drying. The sensitivity of stomatal closure was linked to foliar ABA under drought stress but not under high evaporative demand conditions, suggesting alternative strategies in maize to conserve water.