Obviously there is a temperature range within which the plants can optimally grow and reproduce. Growth and reproduction are less efficient at temperatures above this range. Above a certain temperature, the plants cannot reproduce.
Crops develop more quickly under warmer temperatures, leading to shorter growing periods and lower yields, and that higher temperatures drives faster evaporation of water from soils and transpiration of water from crops.
Many important grain crops tend to have lower yields when summer temperatures increase, primarily because heat accelerates the plant’s developmental cycle and reduces the duration of the grain-filling period (CCSP, 2008a; Rosenzweig and Hillel, 1998).
Exposure to extremely high temperatures (e.g., > 35C) can also cause damage in photosynthetic, reproductive, and other cells, and recent evidence suggests that even short exposures to high temperatures can be crucial for final yield (Schlenker and Roberts, 2009; Wassmann et al., 2009).