Linking Plants Functioning to Adaptive Responses Under Heat Stress Conditions: A Mechanistic Review

The general circulation models estimated an average increase in global surface temperature about 4 °C (2.9 to 5.5 °C). Escalating temperature and extreme weather events are causing higher variations in substantial grain yield losses in cereal crops leading to food insecurity. Temperature flux, more notably high temperature,, affects plants' physio-biochemical processes, resulting in serious yield reduction and quality due to poor agronomic management in plants. Despite the impact of global insecurity on world food production, limited success has been achieved to heat stress adaptation. Extensive research has been made to assess the consequences of abiotic stresses in early growth stages and endurance under subsequent intensity. However, the consequences of abiotic, especially heat/high-temperature stress on reproductive growth, development, and phenology of cereals, received comparatively less consideration, though it has a significant effect on grain yields. Hence, it is imperative to recognize and focus on the most exposed traits of growth and yield under abiotic stress conditions. Among the abiotic stresses, heat stress adversely affects the chlorophyll and grain filling mechanisms in plants. Thus, the preservation of grain weight throughout the heat stress period is also a signal of heat tolerance at the grain filling stage. High potential grain weight under heat stress may also be a better decisive factor for the selection of cultivars for heat tolerance and resistance to changing future climatic conditions. This review summarizes the alterations in the development systems of plants in response to heat stress with a focus on integrated morpho-anatomical, physiological, and molecular adaptations. It also provides information about advanced heat tolerance mechanisms in various plant species applying different tactics together with genetic techniques for plant growth and development.