In
plant morphology, a cataphyll (sometimes also called a cataphyllum[1] or cataphyll leaf[2]) is a reduced, small
leaf.[3] Many plants have both "true leaves" (euphylls), which perform most of the
photosynthesis, and cataphylls, which are modified to perform other functions.[4]
Cataphylls include
bracts,
bracteoles and
bud scales, as well as any small leaves that resemble
scales, known as
scale leaves.[5] The functions of cataphylls, such as bud scales, may be short-lived, and they are often shed after their function is fulfilled.[6]
Etymology
Cataphyll comes from the
Ancient Greekκατά ("kata"), meaning "down", and φύλλον ("phyllon"), meaning "leaf".[7]
Forms
In some cases, cataphylls perform a
transient function, after which they die and may shed. Those that shed early are said to be
caducous. The
sepals of Papaver species are shed during the very opening of the
petals and are a dramatic example of caducous leaves.[citation needed]
Cataphylls can have many other forms. Some, such as
spines,
corm-scales, and
bud-scales, may be
persistent but may not perform their major function until they die, whether or not they are physically shed. Examples of various kinds of living cataphylls include
bulb-scales,
rhizome-scales,
cotyledons, and scaly
bracts.[2] Several of these occur in various forms and contexts. For example, bud scales occur on numerous kinds of leaf or branch buds, as well as on flower buds.[citation needed]
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 is photosynthesis.[citation needed]
Cotyledons as cataphylls
Cotyledons are widely regarded as a class of cataphyll,[8] though many kinds of cotyledons function as living tissue and remain alive until, at least, the end of their function, at which time they wither and may drop off. They begin as leaf
rudiments. Many kinds accumulate nutrient materials for storage, starting to give up their stored material as the plant germinates. Some, such as the
cotyledons of many
legumes,
conifers, and
cucurbits, develop chlorophyll and perform the first
photosynthesis for the germinating plant.[citation needed]
Corm scales
Like bulb-scales,
corm scales are largely the basal parts of the photosynthetic leaves that show up above ground. Some species of
cormous plants, such as some Lapeirousia, also produce cataphylls that act solely as tunic leaves for the corm.[9] Unlike bulb-scales, however, the corm tunic has no significant storage function; that task is left to the
parenchyma of the
cortex of the corm.[citation needed]
Crocosmia corm with tunic stripped partly off to show its constitution of the basal parts of leaves arising from nodes on the corm. Such leaves, especially early leaves that never performed much photosynthesis, amount to true cataphylls.
Corm of Crocosmia, split to show tunic and leaves, as well as a new corm growing from a bud on the
cortex of the old corm.