Pollination
Characteristics of Wind- and Insect-Pollinated Flowers
Bees are essential pollinators | Credit: Shutterstock.com
Pollination is the transfer of pollen, containing the male sex cell, from another to stigma either of the same flower or different flowers and is the essential first step in the process leading to fertilization. |
- Pollination is the transfer of pollen from stamen to stigma of a flower or flowers.
- Fertilization is the fusion of a male sex cell (the male gamete) from a pollen grain with a female sex cell (the female gamete) in the ovule to produce an embryo.
In cross-pollination, pollen transfer is between different plants, while in self-pollination it is within or between flowers on the same plant. The commonest natural agents of pollination are wind and insects.
Representatives of male and female inflorescences of insect- and wind-pollinated Leucadendron species (A = L. salignum , B = L. tinctum , C = L. coniferum , and D = L. teretifolium ). | Source ResearchGateOpens in new window
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Wind-Pollinated Flowers
The characteristics of wind-pollinated flowers (Figure X-1) are their small size, their green appearance (their petals are reduced in size or absent and lack color), their absence of nectarines and scent production, and their production of large amounts of small, smooth, light pollen which is intercepted by large feathery stigmas. They also often have proportionally larger stigmas and flexible stamens that provide from the flower to maximize the chances of dispersing and intercepting pollen grains in the air.
The most common examples of wind-pollinated plants are the grasses, and trees with catkins such as some Salix species (willow), Betula (birch), Corylus (hazel), Fagus (beech) and Quercus (oak). The conifers also use wind pollination to disperse copious amounts of pollen from the small male cones.
Insect-Pollinated Flowers
The characteristics of insect-pollinated flowers (Figure X-1) are brightly colored petals (often with scent production) to attract insects and the presence of nectarines to entice insects with sugary food. Insects such as bees and flies collect the pollen on their bodies as they fly in and out and carry it to other flowers.
Petals may have nectar guides, colored lines to point the way to the nectarines which may only be visible to insects.
Some flowers are designed to favor certain insects — for example, in Antirrhinum majus (snapdragon) and Trifolium repens (clover) the flower physically prevents entry of smaller non-pollinating insects and opens only when heavy bees land on it.
Other plant species, such as Arum italicum (arum lily), trap pollinating insects for a period of time to give the best chance of successful fertilization. The stigmas and stamens of insect-pollinated flowers tend to be short and sturdy and the pollen they produce is larger, heavier and produced in smaller quantities since pollination success is more likely than in wind-pollinated flowers.
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