Breeding for drought tolerance can benefit from a better understanding of possible responses of transpiration to various environmental variables. Temperature and vapour pressure deficit (VPD) are two important factors influencing stomatal conductance and transpiration. In this study, maize (Zea mays L.) plants of four hybrids were grown under three day/night temperature regimes (30/26, 26/22 and 22/18 °C) in glasshouses, and the response of transpiration rate to changes in atmospheric VPD was measured at two different temperatures in a growth chamber. For all the hybrids examined, increases in transpiration rate with increasing VPD were similar and well described by a two-segment linear regression. There was little further increase in transpiration as VPD increased beyond a breakpoint. When measured at high temperature, the breakpoint in transpiration response to VPD occurred at significantly higher VPD and transpiration rate than at low temperature. The effect of growth temperature on transpiration was evident when plants were grown at low temperature (22/18 °C) and measured at higher temperature (30 °C). However, on the second day under the measurement temperature, the transpiration rate of these plants increased to the same level as those grown in higher day/night temperature environments. Limitation on transpiration at high VPD is a promising trait that could be incorporated into breeding programs to improve drought tolerance in maize.

English

Carelia Juarez

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