MANAGEMENT AND DEVELOPMENT
SPECIALIST AND EDUCATOR
The pollination period is one of the most critical stages in the development of a maize plant. By this time the preparation work is done. During the pollination window weather conditions are absolutely crucial. High temperatures, too much rain or drought will hinder effective pollination, which is critical for top yields.
The flowering stage of a maize plant is the most critical period in its development for grain yield.
These are some key steps in the pollination process:
Most maize hybrids tassel and silk about the same time. On a typical midsummer day, peak pollen shed occurs in the morning between 9:00 and 11:00, followed by a second round of pollen shed late in the afternoon.
The pollen shed begins in the middle of the central spike of the tassel and spreads out later over the whole tassel.
Pollen grains are borne in anthers, each of which contains a large number of pollen grains. The anthers open and the pollen grains pour out.
Pollen is light and is often carried considerable distances by the wind. Pollen shed is not a continuous process. It stops when the tassel is too wet or too dry and begins again when temperature conditions are favourable.
Little to no pollen is shed when the tassel is wet, so there is not much chance of pollen being washed off the silks during a rainstorm.
The silks are covered with fine, sticky hairs, which serve to catch and anchor pollen grains.
Pollen grain remains viable for only 18 to 24 hours and the pollen grain starts growth of the pollen tube down the silk channel within minutes of coming in contact with a silk.
The pollen tube grows the length of the silk and enters the female flower (ovule) in 12 to 28 hours.
A well-developed ear shoot should have 750 to 1 000 ovules (the potential kernels) which each produce a silk.
The silks from near the base of the ear emerges first and those from the tip appear last. Under good conditions, all silks will emerge and be ready for pollination within three to five days. This usually provides adequate time to pollinate all silks before pollen shed ceases.
Each tassel contains as many as two million or more pollen grains, which translates to at least 2 000 pollen grains produced for each silk of the ear shoot.
Shortages of pollen are a problem under conditions of extreme heat and drought; they may also occur in fields characterised by uneven emergence in later emerging plants.