Heat tolerance of a tropical-subtropical rainforest tree species Polyscias elegans: time-dependent dynamic responses of physiological thermostability and biochemistry

Abstract

Heat stress interrupts physiological thermostability and triggers biochemical responses thatare essential for plant survival. However, there is limited knowledge on the speed plants adjustto heat in hours and days, and which adjustments are crucial. Tropical–subtropical rainforest tree species (Polyscias elegans) were heated at 40°C for 5 d,before returning to 25°C for 13 d of recovery. Leaf heat tolerance was quantified using thetemperature at which minimal chl a fluorescence sharply rose (Tcrit ). Tcrit , metabolites, heatshock protein (HSP) abundance and membrane lipid fatty acid (FA) composition were quanti-fied. Tcrit increased by 4°C (48–52°C) within 2 h of 40°C exposure, along with rapid accumula-tion of metabolites and HSPs. By contrast, it took > 2 d for FA composition to change. At least2 d were required for Tcrit , HSP90, HSP70 and FAs to return to prestress levels. The results highlight the multi-faceted response of P. elegans to heat stress, and how thisresponse varies over the scale of hours to days, culminating in an increased level of photosyn-thetic heat tolerance. These responses are important for survival of plants when confrontedwith heat waves amidst ongoing global climate change Show more