Should plants keep their (canopy) ‘cool’ or allow themselves to grow ‘warm’ under stress: It is a Hobson’s choice and plants survive by doing a balancing act

Abstract

Two drought postponement strategies are put into operation in plants when the soil starts to dry. Ironically, one results in ‘cooler’ canopies (maintains transpiration (T) by keeping stomata open) and the other initiates a cascade of events leading to closure of stomata and the consequent ‘warming’ of canopies. The ‘dilemma’ of plants is which of these two strategies to operate at what time and for how long. Our studies suggest that it is a Hobson’s choice for plants as both processes have distinct advantages and disadvantages. In this paper we discuss why, how and when the plant makes the choice between these two strategies when it is undergoing a long drought in the field. We also briefly discuss the metabolic costs involved in adapting either of these strategies and the balancing act a plant does, not to just survive, but maximize carbon gain in a difficult catch 22 situation.