Pollination and Fertilization of corn

For those interested in semantics,let's review two definitions related to sex in the cornfield.Pollination is the act of transferring pollen grains to silk by wind or insects.Fertilization is the union of male gametes from pollen with female gametes from ovules.Technically, pollination is almost always successful (i.e.pollen reaches filaments),but unsuccessful fertilization (i.e. pollen tube failure,filament failure, pollen death) will result in poor kernel set and yield loss.Pollen grain germination occurs within minutes after a pollen grain lands on a receptive filament.Pollen tubes containing the male genetic material develop and grow within the silk and fertilize the ovules within 24 hours.Pollen grains can land and germinate anywhere along the length of the exposed receptive filament.Many pollen grains may germinate on the receptive filament, but usually only one successfully fertilizes the ovule.

Silk Responses to Severe Stress 

severe drought stress.The most common cause of incomplete silking is severe drought stress.The silk has the highest water content of any maize plant tissue and is therefore the most sensitive to the amount of water in the plant.Severe moisture deficits can slow silk elongation,causing delayed or no silk emergence from ear buds.If the delay is long enough,pollen release may be almost or completely complete before acceptor filaments are available;resulting in nearly or completely blank cobs.In addition to causing silk failure,severe drought stress,especially when accompanied by high temperature and low relative humidity,can also dry out the exposed silk,making it unreceptive to pollen germination.Effects of drought stress on silk receptivity may be more prevalent than pollen availability or vigor in the Eastern Corn Belt.The severity of drought stress required for a significant delay in silk emergence or drying may be characterized by severe leaf curling beginning in the early morning and continuing into the evening.This severe leaf rolling is often accompanied by an initial change in leaf color from a "healthy" green to a grayish green before the leaves eventually die.Insect cut wire,Severe silk clipping by insects such as the corn rootworm beetle or the Japanese beetle can interfere with pollination success by reducing or eliminating live or receptively exposed silk tissue.Fortunately,unless the beetle is in constant activity for several days without interruption,the continuous elongation of the filament within the shell will expose the undamaged receptive filament tissue at a rate of about an inch or more per day.Silk "balls",Sometimes silking does not appear successfully because they do not follow the usual straight "path" from the ovule to the end of the shell leaf.Instead,silk elongations are coiled (twisted,coiled,tangled) within the shell leaf.This spinning "balling" phenomenon is not well understood and hybrids tend to vary in their susceptibility to this spinning failure.Two different pieces of circumstantial evidence are usually relevant to the question.One is the physical restriction on silk elongation imposed by unusually 'tight' or long husk leaves in some hybrids.Another situation often associated with silk "pilling" is unusually cool nights during silk elongation but before silk emerges. The physiological impact of such cool nights on silk elongation is unknown.It has been several years since I last saw a field with a lot of silk "pilling".