Any reproductive process that does not involve meiosis or syngamy is said to be asexual, or vegetative. The absence of syngamy means that such an event can occur in the sporophyte generation or the gametophyte stage. Because of the lack of new genetic material, an organism clones itself through this process and makes genetically identical organisms. This can be advantageous in some circumstances, but deleterious in others, depending on how the makeup of the plant suits its ecosystem. There are a few major ways in which plants asexually reproduce in their life cycles to secure future generations.
New plants can grow by the separation of parts of the original plant. When fragmentation, or division, occurs, an offspring is created by the breakup of a single part of the plant. By planting parts of the tuber of a potato, one can create new organisms with the same genetic makeup. When weeds are broken apart, they can regrow from each fragmented underground stem. In Marchantia, fragmentaion of the thallus gives rise to vegitative reproduction. When rain drops hit the plants, these structures are splashed out and may germinate into completely new plants. With these vegetative structures, many clones can be formed from one original parent. Bulbs and Rhizomes are also examples of asexual reproduction.
Special dispersal structures such as a capsule and a hood, and mini adults may also aid a plant when it reproduces asexually. Gemma cups are an example of a dispersal structure that leads to a genetically identical organism. With mini-adults, the morphology of the reproductive unit is similar to that of the parent. A plant may produce plantlets (mini plants) on its stems or leaves that will later germinate into clones of the original.
Finally, some plants have developed a way to produce seeds without their flowers being fertilized. In apomixis, an embryo is created from a diploid cell in the ovule. Then the ovules mature into seeds. The dandelion is one plant that uses this form of vegitative reproduction.
Asexual reproduction can be advantageous and/or disadvatageous. One positive aspect is that it can create individuals rapidly and in large quantities. Secondly, bypassing the sexual process can help a plant in times of dryness since motile sperm require water to fertilize the egg. Another advantage lies in the fact that plants with the desired characteristics can be cloned for economic reasons (agriculture). However, if something goes wrong, such as as the occurance of a fatal mutation, the whole society of clones can be terminated. For this reason, farmers are careful in determining how to propagate their vegetation. In conclusion, the asexual process of reproduction is an important one to plants.
Meiosis and Syngamy |
| Evolution of Life Cycles |
| Haploid Life Cycle | Diploid Life Cycle | Haploid-Diploid Life Cycle |
| Ecology of Reproduction | Asexual Reproduction | Summary |
| Sources | G lossary |