Chimera (plant)
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[[Image:Ficus.Benjamina.Chimera.jpg|thumb|right|250px|''[[Ficus Benjamina]]'' [[L.]] Variegated chlorophyll-deficient chimera. ]]
'''Chimeras''' (or "chimaeras") in [[botany]] are usually single organisms composed of two genetically different types of tissue. They occur in [[plant]]s, on the same general basis as with [[Chimera (genetics)|animal chimeras]]. However, unlike animal chimeras, both types of tissues may have originated from the same [[zygote]], and the difference is often due to [[mutation]] during ordinary [[cell division]].
==Types of plant chimera==
===Variegated plants===
The best-known plant chimeras are those cultivated for their [[variegation]]. Generally the genetic difference is due to [[mutation]] in [[meristem]]atic tissue of a normal plant. For most variegation, the mutation involved is the loss of the [[chloroplast]]s in the mutated tissue, so that part of the plant tissue has no green pigment and no [[Photosynthesis|photosynthetic]] ability. This mutated tissue is unable to survive on its own but is kept alive by its partnership with the normal, photosynthesising tissue.
===Thornless plants===
Other types of chimera are valued by [[gardener]]s and other [[horticulturist]]s because the skin tissue lacks the [[Spine (biology)|spine]]-producing characteristic of the underlying tissue.
===Graft-chimeras===<!-- This section is linked from [[Potato]] -->
A distinct type of plant chimera is the [[Graft-chimaera|graft-chimera]] (or, incorrectly, graft-hybrid), involving tissues from two genetically different parents, different [[cultivar]]s or different species (which may belong to different genera). The tissues may be partially fused together following [[grafting]] to form a single growing organism that preserves both types of tissue in a single shoot. The first such known chimera was probably the [[Bizzaria]] which is a confusion of the [[Florentine Citron]] and the [[sour orange]]. Perhaps the best-known example of this is [[+Laburnocytisus 'Adamii'|+''Laburnocytisus'' 'Adamii']], caused by a fusion of a ''[[Laburnum]]'' and a [[Broom (shrub)|broom]].
==Propagation==
Because chimeras have more than one type of genetic material, while they may produce viable offspring from [[seed]], these will not be true to type. All [[Plant propagation|propagation]] that preserves the variation has to be by [[Cutting (plant)|cuttings]] or division. Some types of cuttings, such as root cuttings, will produce entirely new growing points, usually from the inner one of the two types of tissue, so that these cannot be used either.
==Derivation==
The word chimera in these senses is a reference to the monstrous [[Chimera (mythology)|chimera]] of ancient [[Greek mythology]], a legendary beast made up of parts of several different animals.
[[Category:Botany]]