Raffi at 03:53, 6 April 2007

2007-04-06T03:53:43Z

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[[image:Kalanchoe_veg.jpg|thumb|350px|right|Production of new individuals along a leaf margin of the air plant, ''Kalanchoë pinnata''. The small plant in front is about 1 cm tall. The concept of "individual" is obviously stretched by this process.]]

'''Vegetative reproduction''' is a type of [[asexual reproduction]] found in plants also called '''vegetative propagation''' or '''vegetative multiplication'''. It is a process by which new [[plant]] "individuals" arise or are obtained without production of [[seed]]s or [[spore]]s. It is both a natural process in many plant species (including organisms that may or may not be considered "plants", such as bacteria and fungi) and one utilized or encouraged by [[horticulture|horticulturists]] to obtain quantities of economically valuable plants.

Natural vegetative reproduction is mostly a [[process]] found in [[herbaceous plant|herbaceous]] and [[wood]]y [[perennial plant|perennial]] plants, and typically involves structural modifications of the [[Plant stem|stem]], although any horizontal, underground part of a plant (whether stem or a [[root]]) can contribute to vegetative reproduction of a plant. And, in a few species (such as ''[[Kalanchoe|Kalanchoë]]'' shown at right), [[leaf|leaves]] are involved in vegetative reproduction. Most plant species that survive and significantly expand by vegetative reproduction would be perennial almost by definition, since specialized organs of vegetative reproduction, like seeds of annuals, serve to survive [[season]]ally harsh conditions. A plant that persists in a location through vegetative reproduction of individuals over a long period of time constitutes a [[clonal colony]].

In a sense, this process is not one of "reproduction" but one of survival and expansion of biomass of the individual. When an individual organism increases in size via cell multiplication and remains intact, the process is called "vegetative growth". However, in vegetative reproduction, the new plants that result are new individuals in almost every respect except genetic. And of considerable interest is how this process appears to reset the aging clock.

== Natural vegetative structures ==
The '''[[rhizome]]''' is a modified stem serving as an organ of vegetative reproduction. Prostrate aerial stems, called '''runners''' or '''[[stolon]]s''' are important vegetative reproduction organs in some species, such as the [[strawberry]], numerous [[Poaceae|grasses]], and some [[fern]]s. '''Adventitious''' buds develop into above ground stems and leaves, forming on roots near the ground surface and on damaged stems (as on the stumps of cut trees). ''Adventitious'' roots form on stems where the latter touch the soil surface.

A form of budding called '''[[Basal shoot|suckering]]''' is the reproduction or [[regeneration (biology)|regeneration]] of a plant by shoots that arise from an existing [[root system]]. Species that characteristically produce suckers include [[Elm]] (''Ulmus''), [[Dandelion]] (''Taraxacum''), and members of the [[Rose]] Family (''Rosa'').

Another type of a vegetative reproduction is the production of [[bulb]]s. Plants like [[onion]] (''Allium cepa''), [[Hyacinth (flower)|hyacinth]] (''Hyacinth''), [[narcissus (flower)|narcissus]] (''Narcissus'') and [[tulip]]s (''Tulipa'') reproduce by forming bulbs. Other plants like [[potato]]es (''Solanum tuberosum'') and [[dahlia]] (''Dahlia'') reproduce by a similar method of producing [[tuber]]s. [[Gladiolus]]es and [[crocus]]es (''Crocus'') reproduce by forming a bulb-like structure called a [[corm]].

==Exceptions==
Vegetative propagation is usually considered a cloning method. However, there are several cases where vegetatively propagated plants are not genetically identical. Rooted stem cuttings of thornless blackberries will revert to thorny type because the adventitious shoot develops from a cell that is genetically thorny. Thornless blackberry is a [[chimera (plant)|chimera]], with the epidermal layers genetically thornless but the tissue beneath it genetically thorny. Leaf cutting propagation of certain chimeral variegated plants, such as snake plant, will produce mainly nonvariegated plants.

Grafting is often not a complete cloning method because sexual seedlings are used as rootstocks. In that case only the top of the plant is clonal. In some crops, particularly apples, the rootstocks are vegetatively propagated so the entire graft can be clonal if the scion and rootstock are both clones.

'''[[Apomixis]]''' is a type of asexual reproduction involving unfertilized seeds. [[Hawkweed]] (''Hieracium''), [[dandelion]] (''Taraxacum''), some [[Citrus]] (''Citrus'') and [[Kentucky blue grass]] (''Poa pratensis'') all use this form of asexual reproduction. Bulbils are sometimes formed in the flowers of [[garlic]]. The leafy crown of a [[pineapple]] fruit will root to form a new plant. These cases would not be vegetative reproduction because normally reproductive parts were involved. They would be considered asexual reproduction however. Vegetative reproduction involves only vegetative structures, i.e. roots, stems or leaves.

== Horticultural aspects ==
Man-made methods of vegetative reproduction are usually enhancements of natural processes, but range from simple [[cloning]] such as rooting of cuttings to [[grafting]] and artificial propagation by laboratory [[Plant tissue culture|tissue cloning]]. It is very commonly practised to propagate [[cultivar]]s with individual desirable characteristics. [[Fruit tree propagation]] is frequently performed by budding or grafting desirable cultivars ([[cloning|clone]]s), onto [[rootstock]]s that are also clones, propagated by [[layering]].

In horticulture, a "cutting" is a branch that has been cut off from a mother [[plant]] below an [[internodes|internode]] and then rooted, often with the help of a [[rooting powder|rooting liquid or powder]] containing [[plant hormone|hormones]]. When a full root has formed and leaves begin to sprout anew, the clone is a self-sufficient plant, genetically identical to the mother plant. Examples are cutting from the stems of [[Blackberry|blackberries]] (''Rubus occidentalis''), cutting from leaves of [[African violet]]s (''Saintpaulia''), and cutting the stems of [[Vervain|verbena]]s (''Verbena'') to create new plants. A related form of regeneration is that of [[grafting]]. This is a process of taking a bud and grafting onto a plants stem. Many [[Nursery (horticulture)|nurseries]] now sell trees that can produce four or more varieties of [[apple]]s (''Malus spp''.) from stems grafted to a common rootstock.

=== Cultivated plants propagated by vegetative methods ===
A number of commonly cultivated plants are propagated by vegetative means rather than by seeds. This is a listing of such plants:
:[[Apple]]
:[[Avocado]]
:[[Banana]]
:[[Cacao]]
:[[Canna (plant)|Canna]]
:[[Citrus]] ([[lemon]], [[Orange (fruit)|orange]], [[grapefruit]])
:[[Date (fruit)|Date]]
:[[Fig]]
:[[Manioc]] (cassava)
:Nut crops ([[walnut]], [[pecan]])
:[[Pineapple]]
:[[Pear]]
:[[Poplar]]
:[[Potato]]
:[[Strawberry]]
:[[Sugar cane]]
:[[Tea]]
:[[Vanilla]]
:[[Willow]]

==See also==
* [[Spore]]s
* [[Regeneration (biology)|Regeneration]]

[[Category:Plant reproduction]]

Vegetative reproduction - Revision history

Raffi at 03:53, 6 April 2007