35.5: Asexual Reproduction
Asexual reproduction allows plants to reproduce without growing flowers, attracting pollinators, or dispersing seeds. Offspring are genetically identical to the parent and produced without the fusion of male and female gametes.
Vegetative reproduction is a common type of asexual reproduction, in which detached fragments—such as stems, roots, or leaves—from individual plants develop into complete organisms. Dandelions of the Taraxacum genus use a method of asexual reproduction called apomixis, which produces seeds without pollination or fertilization.
Plant breeders also use artificial methods of asexual reproduction—including cutting, grafting, layering, and micropropagation.
Some plants can be propagated by merely placing stem cuttings that contain nodes into moist soil and allowing them to root.
Grafting can be used to combine the desirable traits of different plants. A stem segment (the scion) from one plant is grafted, or attached, to a root section (the stock) from another plant. Over time, the vascular systems of the two plants fuse, forming a graft. The scion grows, producing new shoots and eventually flowers and fruit. Grafting is typically used to produce different varieties of grapes, roses, and citrus trees, among other species.
Layering involves bending a young stem of a plant and covering the stem with soil. Rooting hormones may also be applied. When roots appear, the new plant can be transplanted to a different area.
Micropropagation quickly produces several plants from a single plant using plant tissue culture methods. These techniques are useful for propagating rare or endangered species that are difficult to grow in natural conditions.
While asexual reproduction confers several advantages, strictly asexually-reproducing species are at an increased risk of extinction. Asexual reproduction can reduce genetic variability, limiting an organism’s ability to adapt to changing environmental conditions.