Heat, water and corn

​Every corn growing season differs in two important factors affecting plant height and flowering of corn plants.  The growing point of the corn plant continues to produce new cells until the V5 (5 visible leaf collars). At that time, the new cells differentiate to produce the tassel cells. It is elongation of those cells that determines the plant height.  Pressure from the water transported through the xylem to the upper plant tissue and newly formed cells causes the cells to elongate. Heat energy, interacting with the genetics, determined the change in cells produced by the apical meristem from producing more stem and leaf cells to tassel cells. This genetically affected trait has allowed a tropical plant to be adapted to temperate zones around the earth.
 
Seasons and environments differ in both water and heat with the consequence of important corn productivity factors including leaf area, accumulations of carbohydrates, timing from planting to harvest, uptake of minerals, number of kernels per ear and ultimately grain yield.  Early season hot and dry weather results in shorter plants and early flowering.  Continuation of excessive heat increases evaporation of water through stomates, potentially dehydrating leaf cells, affecting photosynthesis in chloroplasts and flow of glucose through phloem in vascular system to roots and newly formed kernels.
 
Timing of excessive heat or drought is significant to the final season affect on grain production and standability of the corn crop. Corn breeders select genetics that tend to perform well in multiple environments, but all are affected when heat is unusually hot and soils are extra dry.