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cataphyll
In plant morphology, a cataphyll (sometimes also called a cataphylla, or cataphyll leaf〔Jackson, Benjamin, Daydon; A Glossary of Botanic Terms with their Derivation and Accent; Published by Gerald Duckworth & Co. London, 4th ed 1928〕) is a leaf whose primary function is something other than photosynthesis. Cataphylls are at most trivially or transiently photosynthetic, and instead of photosynthesis the main functions of most types are storage, protection, or structural support. Many forms of cataphylls die in performing their function. Cataphylls such as bud scales often are shed after the need for them is past, but dead cataphylls that afford protection from weather or pests may be accumulated into long-lasting, thick coverings.
==Forms of cataphylls==
Some kinds of cataphylls perform a transient function, after which they die and may be shed. Those that are shed early are said to be caducous, but that term can apply to any organ that is shed early, not only leaves; for example, many ''Geraniums'' have caducous stamens. The sepals of ''Papaver'' species are shed during the very opening of the petals, and as such they are a dramatic example of caducous leaves. Many other forms of cataphylls, such as some spines, are persistent, but cannot perform their major function until they die, whether they physically get shed or not. Yet others perform indefinitely in the form of persistent structures that remain on the plant after they die. Examples of various kinds of cataphylls include bud-scales, bulb-scales, corm-scales, rhizome-scales, cotyledons, scaly bracts, spines and perhaps glochids.〔 Each of these occurs in various forms and contexts; for example, bud-scales occur on various kinds of leaf or branch buds as well as on flower buds.
At all events, cataphylls are in general ''sacrificial organs''; their function is not related to their own survival, but in direct or indirect support of the propagation of the parent organism.
The word ''cataphyll'' derives from the Greek; in context it means something like "leaf to be broken down", implying leaves that are discarded or consumed. In fact some forms of cataphylls, such as the leaves or leaf bases forming the tunic around a corm or a bulb, are retained after they have died, and the protective presence of their remains is their major function. Similar protective masses of dead leaves encircle the stems of some species of palm trees or ''aloes'', but those are not usually regarded as cataphylls because their primary function while alive was photosynthesis, as is usual for leaves. Clearly, the precise limits of the definition of the concept is a matter of convenience in any given context.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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