Out of Darkness: Nocturnal Transpiration and Its Circadian Control As Contributors of Drought Tolerance in Crops
(2019) ASA, CSSA and SSSA International Annual Meetings — Location: San Antonio (Texas) (10.November.2019)
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- Abstract
- In crops, nocturnal transpiration rate (TRN) is often assumed to be negligible, despite findings on trees indicating that decreases in TRN may save water needed for daytime CO2 fixation. Furthermore, recent evidence on trees indicates that circadian control of TRN may be beneficial for drought adaptation by “priming” stomata to maximize gas exchange before the challenging midday conditions. In this work, we addressed the following questions: i) is TRN non-negligible in crops? ii) is it genotypically variable? iii) is TRN circadially controlled? and iv) do these findings indicate opportunities to enhance drought tolerance? To this end, we used a gravimetric phenotyping system to screen maize, wheat and maize diversity panels, totaling 129 genotypes. Within all species, we found that TRN is largely variable across genotypes (up to 2.5-fold variation), representing up to ∼15% or 30% of the daytime TR dependently of whether the latter is measured under a low or high daytime evaporative demand. In addition, we found that under drought, TRN represents an increasing fraction of daily water loss at least in wheat. Furthermore, in all species, TRN was found to exhibit a pre-dawn increase under constant environmental conditions, indicating that it is partly controlled by the circadian clock. In wheat, the slope of this increase was found to correlate with canopy conductance and is putatively under selection by Australian breeders as it has been increasing in a year-of-release-dependent fashion. In barley, this slope negatively correlated with precipitation from germplasm’s areas of origin, such that drought-adapted lines exhibited a stronger circadian control of TRN. Collectively, the findings indicate that breeding for reduced TRN but with high rates of pre-dawn increase in the late hours of the night would be a useful drought tolerance strategy, by minimizing “wasteful” nighttime water loss and maximizing early morning water use efficiency.
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Sadok, W., Tamang, B., Schoppach, R., Steffenson, B., & Anderson, J. A. (2019). Out of Darkness: Nocturnal Transpiration and Its Circadian Control As Contributors of Drought Tolerance in Crops. ASA, CSSA and SSSA International Annual Meetings, San Antonio (Texas). https://hdl.handle.net/2078.5/220108