Corn seedlings and low temperatures

​Spring temperatures in temperate zones are variable.  Movement of maize from its central Mexico origin to much cooler and variable environments required many years of selection for performance under temperature stresses not experienced by its ancestors.  Fortunately, the genetic variability within corn and the efforts by people to select for adaptation has resulted in varieties that survive at above freezing temperatures.
 
Low temperatures do result in some reduction in photosynthesis in seedlings but the biggest response is in other metabolism affecting most growing plant functions. Cell division and cell elongation are greatly reduced as the temperature approaches 50° and probably stops at lower temperatures.  Metabolism in these young leaves includes creation of more chloroplasts, affecting the color of the new leaves as they slowly emerge with a yellowish color.  Cell elongation is reduced under cooler temperatures causing the new leaves to be shorter than when grown under higher temperatures.
 
Movement of the sugars produced by photosynthesis from leaf tissue to the new meristem cells and root tissues is a metabolic-driven process. Consequently, sugars can accumulate in the leaf tissue when corn seedlings are too cool.  Accumulation of water soluble sugars could have a negative effect on the osmosis of cells, essentially dehydrating them.  One adaptation for this condition is production of the red pigment anthocyanin in leaves, resulting in a reduction of photosynthesis.  Hybrids differ in occurrence of red leaves when seedlings are exposed to low temperatures.  It is temporary and is not thought to have effect on final productivity of the plants.
 
Genotypes vary in response to low temperatures.  This can cause hybrid seed production problems in that it affects the timing of flowering between the two parents.  If the male parent development reacted to low early season temperatures more than the female parent, the result can be little pollen at the time the female parent plants are silking. This can result in less seed and higher probability of genetic purity problems.  Seed producers develop strategies to negate this potential as it is part of the seed business.