The vapor pressure deficit (VPD) between the leaf and the atmosphere is the driving force behind transpiration, which supplies plants with water and nutrients, but at the same time causes water to be lost from the plant. As the atmosphere warms, the VPD increases, and with it, water loss. Plants regulate their water balance by opening and
closing their stomata. Their response to environmental conditions, such as soil or atmospheric drought, varies from plant species to species and depends, among other factors, on the anatomical structure of the stomata. In this study, we investigated the dynamics of stomatal response to changes in VPD in two corn hybrids that are classified as having different levels of drought tolerance ('P8834' Aquamax and 'P9363'; Corteva Agriscience™). Half of the plants were exposed to misting (lower VPD) for a few hours each day, while the other half grew under actual conditions (higher VPD); in part of the experiment, the plants were also watered differently. We investigated the effects of
acclimation to lower VPD, hybrids, and substrate moisture on the anatomy of leaf stomata and their response to different VPD values; however, due to fogging that was not intense enough and insufficiently controlled, we were unable to achieve the desired range of VPD values. The anatomy of the stomata differed between the hybrids from the outset, and after acclimatization, further changes occurred between the treatments; however, we cannot assert that this was a result of the conditions we established. With a moderate increase in VPD, the tolerant hybrid closes its stomata more quickly than the intolerant hybrid, while the control plants close their stomata more quickly than the mist-treated plants. When transferred from a lower to a higher VPD, non-irrigated plants restrict stomatal conductance more than irrigated plants. The tolerant hybrid and plants growing under more stressful conditions exhibit greater stomatal sensitivity.
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