Corn is a globally significant crop, providing food for humans and livestock, and serving as a raw material for various industries. The successful development of corn kernels, which are the edible and economically valuable part of the plant, relies entirely on a process called pollination. Understanding how this process unfolds is important for maximizing corn yield and ensuring food security.
Unique Corn Anatomy
The corn plant possesses distinct male and female reproductive structures on the same plant, a characteristic known as monoecious. The male flower, called the tassel, develops at the top of the plant. This branched structure produces and releases pollen grains. Meanwhile, the female flowers are found lower down on the stalk, encased within protective husks, forming the corn ear.
Each potential kernel on an ear is connected to a single strand called a silk. These silks emerge from the tip of the ear and are fine, sticky hairs. The physical separation of the tassel and the ear, along with the distinct roles of these structures, are fundamental to corn’s pollination strategy.
The Pollination Process
Corn relies on wind for pollination. Pollen release begins when the anthers on the tassel open. A single corn plant can produce a substantial amount of pollen, ranging from 2 to 5 million grains, with shedding usually occurring over a 10 to 14-day period. Most pollen falls within 20 to 50 feet of the plant from which it was shed, though it can travel further.
The silks are covered with fine, sticky hairs that efficiently capture airborne pollen grains. Each silk is connected to a single ovule (a potential kernel) within the developing ear. Upon landing on a silk, a pollen grain germinates, extending a pollen tube down the length of the silk. This tube grows towards the ovule, a journey that takes 12 to 28 hours.
From Pollination to Kernel Development
Once the pollen tube reaches an ovule, fertilization occurs. Each fertilized ovule transforms into a kernel, forming the rows on the corn cob. The silks that have been pollinated and fertilized will then detach and begin to dry and turn brown.
The grain fill period, during which kernels develop, begins after pollination and continues for 60 days until maturity. Around 10 to 14 days after silking, the developing kernels are in the “blister stage.” As development progresses, the kernels accumulate starch, passing through milk and dough stages before reaching full maturity. A full ear of corn depends on the pollination of many silks.
Factors Influencing Pollination Success
Several environmental and physiological factors can impact corn pollination. Temperature plays a role, as extreme heat can reduce pollen viability and damage exposed silks. Pollen shed is also influenced by moisture; it can stop if the tassel is too wet or too dry.
Wind conditions are also important, as wind is the primary vector for pollen dispersal. Insufficient or excessive wind can hinder effective pollen transfer. Drought stress is a significant challenge, as it can delay silk emergence and elongation while potentially accelerating pollen shed, leading to a mismatch in timing. This desynchronization can result in poor kernel set. Planting density can also affect wind flow through the crop, indirectly influencing pollen distribution.