Cross pollinating with another plant and not even necessarily of the same species! A plant with genes dominant only XX only makes dominant XX. Crossed with itself, that's all you'll ever get.
Add in another set of genes and you could get XX, Xx, or xx! And that's for just one set of traits. Overall, self pollination reduces variation by limiting the available pool of allele types to work with. Flowering plants have co-evolved with their pollinator partners over millions of years producing a fascinating and interesting diversity of floral strategies and pollinator adaptations.
The great variety in color, form, and scent we see in flowers is a direct result of the intimate association of flowers with pollinators. The various flower traits associated with different pollinators are known as pollination syndromes. Flowering plants have evolved two pollination methods: 1 pollination without the involvement of organisms abiotic , and 2 pollination mediated by animals biotic.
Plants that use wind for cross-pollination generally have flowers that appear early in the spring, before or as the plant's leaves are emerging.
This prevents the leaves from interfering with the dispersal of the pollen from the anthers and provides for the reception of the pollen on the stigmas of the flowers. In species like oaks, birch, or cottonwood, male flowers are arranged in long pendant catkins or long upright inflorescences in which the flowers are small, green, and grouped together, and produce very large amounts of pollen.
Pollen of wind-pollinated plants is lightweight, smooth, and small. Grasslands ensure successful wind pollination through sheer number of flowering plants and the large quantities of pollen released.
Photo by U. Forest Service. Inset photo: A grass plant Bouteloua gracilis in anthesis anthers releasing pollen. Photo by Steve Olson. Some plants such as Erythronium grandiflorum stagger the timing of pollen release to increase visitation by pollinators and lower the chances of self-pollination. Wind-pollinated species like this cottonwood releases copious amounts of pollen from its catkins before the tree leafs out. Female gametes are found in the ovules of a flower.
Pollination is the process that brings these male and female gametes together. The wind or animals, especially insects and birds, pick up pollen from the male anthers and carry it to the female stigma. Flowers have different shapes, colours and smells, and often sugary nectar and nutritious pollen, to encourage animals to visit and pollinate them. Wind-pollinated flowers are shaped to make it easy for the wind to pick up or deposit pollen. Many flowers can be pollinated by their own pollen — a process called self-pollination.
However, this does not always result in the genetic variation needed for species to survive. Many plants have ways to make sure they are only pollinated by pollen from a flower on a different plant, which is called cross-pollination.
Some have the male and female parts in separate flowers on the same plant, while others have male and female flowers on different plants. Many have the stigmas and anthers ripening at different times to prevent self-pollination. In gymnosperms, pollination involves pollen transfer from the male cone to the female cone. Upon transfer, the pollen germinates to form the pollen tube and the sperm for fertilizing the egg. Pollination has been well studied since the time of Gregor Mendel.
Mendel successfully carried out self- as well as cross-pollination in garden peas while studying how characteristics were passed on from one generation to the next. Interestingly, though these two plants appear to be entirely different, the genetic difference between them is miniscule. Pollination takes two forms: self-pollination and cross-pollination. Self-pollination occurs when the pollen from the anther is deposited on the stigma of the same flower, or another flower on the same plant.
Cross-pollination is the transfer of pollen from the anther of one flower to the stigma of another flower on a different individual of the same species. This method of pollination does not require an investment from the plant to provide nectar and pollen as food for pollinators.
0コメント