Plant reproduction
Natural vegetative reproduction is a process mostly found in perennial plants, and typically involves structural modifications of the stem or roots and in a few species leaves.
A plant that persists in a location through vegetative reproduction of individuals gives rise to a clonal colony.
When an individual organism increases in size via cell multiplication and remains intact, the process is called vegetative growth.
Hawkweeds (Hieracium), dandelions (Taraxacum), some species of Citrus and Kentucky blue grass (Poa pratensis) all use this form of asexual reproduction.
Pseudogamy occurs in some plants that have apomictic seeds, where pollination is often needed to initiate embryo growth, though the pollen contributes no genetic material to the developing offspring.
Prostrate aerial stems, called runners or stolons, are important vegetative reproduction organs in some species, such as the strawberry, numerous grasses, and some ferns.
A form of budding called suckering is the reproduction or regeneration of a plant by shoots that arise from an existing root system.
Species that characteristically produce suckers include elm (Ulmus)[4]: 299 and many members of the rose family such as Rosa,[4]: 285–296 Kerria[4]: 206 and Rubus.
The most common form of plant reproduction used by people is seeds, but a number of asexual methods are used which are usually enhancements of natural processes, including: cutting, grafting, budding, layering, division, sectioning of rhizomes, roots, tubers, bulbs, stolons, tillers, etc., and artificial propagation by laboratory tissue cloning.
When a full root has formed and leaves begin to sprout anew, the clone is a self-sufficient plant,[7] genetically identical.
Nurseries offer for sale trees with grafted stems that can produce four or more varieties of related fruits, including apples.
The fusion of male and female gametes (fertilization) produces a diploid zygote, which develops by mitotic cell divisions into a multicellular sporophyte.
The mature sporophyte produces spores by meiosis, sometimes referred to as reduction division because the chromosome pairs are separated once again to form single sets.
In the evolution of early plants, abiotic means, including water and much later, wind, transported sperm for reproduction.
Seed producing plants, which include the angiosperms and the gymnosperms, have a heteromorphic alternation of generations with large sporophytes containing much-reduced gametophytes.
Sexual reproduction in flowering plants involves the production of separate male and female gametophytes that produce gametes.
The pollen grains attach to the stigma on top of a carpel, in which the female gametophytes (inside ovules) are located.
After pollination occurs, the pollen grain germinates to form a pollen tube that grows through the carpel's style and transports male nuclei to the ovule to fertilize the egg cell and central cell within the female gametophyte in a process termed double fertilization.
Plants have a number of different means to attract pollinators including color, scent, heat, nectar glands, edible pollen and flower shape.
The stamens are modified to produce pollen in clusters called pollinia, which become attached to insects that crawl into the flower.
If the spores are deposited onto a suitable moist substrate they germinate to produce short, thin, free-living gametophytes called prothalli that are typically heart-shaped, small and green in color.
Bryophytes are typically small plants that grow in moist locations and like ferns, have motile sperm which swim to the ovule using flagella and therefore need water to facilitate sexual reproduction.
Bryophytes show considerable variation in their reproductive structures, and a basic outline is as follows: Haploid gametes are produced in antheridia and archegonia by mitosis.
By delaying the release of some of its seeds, the cactus can protect these from potential threats from insects, herbivores, or mold caused by micro-organisms.
A study found that the presence of adequate water in the environment causes M. Hernandezii to release more seeds to allow for germination.
The plant was able to perceive a water potential gradient in the surroundings, and act by giving its seeds a better chance in this preferable environment.
