Heat response, senescence and reproductive development in plants.

Heat stress (HS)-induced reduction in crop productivity is likely to enhance because of the impending climate change. HS affects both vegetative and reproductive phase in plants leading to loss in yield. HS at the vegetative stage results in less biomass accumulation and at reproductive stage anther development is particularly susceptible to heat episodes in crops. Heat acclimation is a major protective mechanism in plants enabling survival under HS in the field. Development of thermotolerance is associated with reactive oxygen species (ROS), sugar and hormone signalling, expression of heat-shock transcription factors (HSFs) genes and activation of heat-shock proteins (Hsps), enhancement in antioxidant capacity, accumulation of compatible solutes etc. HS can induce/accelerate monocarpic senescence in crops, and hasten the process of grain development by shortening the duration and enhancing the growth rates of developing sinks leading to shrivelled grains. More studies are needed to address species-specific physiological criteria for HS tolerance to define climate change vulnerability of crops and breeding of HS-tolerant genotypes. There is a need to understand the mechanism/s enabling pollen fertility under HS in crops in order to reduce the yield loss. In this chapter we discuss current understanding of HS effect on leaf senescence, reproductive development and mechanisms enabling heat-stress tolerance with special emphasis on ROS, sugar metabolism, Hsps and transcription factors (TFs).