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Leaf window, also known as epidermal window, and fenestration. is a specialized
leaf A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, ...
structure consisting of a translucent area through which light can enter the interior surfaces of the leaf where
photosynthesis Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored in ...
can occur. The translucent structure may include epidermal tissue, and in some succulent plants it consists of several cell layers of
parenchyma Parenchyma () is the bulk of functional substance in an animal organ or structure such as a tumour. In zoology it is the name for the tissue that fills the interior of flatworms. Etymology The term ''parenchyma'' is New Latin from the word ...
, which may also function as water-storage tissue. It can appear as a large continuous patch, a variegated or reticulated region, or as numerous small spots. Is found in some
succulent plant In botany, succulent plants, also known as succulents, are plants with parts that are thickened, fleshy, and engorged, usually to retain water in arid climates or soil conditions. The word ''succulent'' comes from the Latin word ''sucus'', meani ...
s native to arid climates, allowing much of the plant to remain beneath the soil surface where it is protected from desiccation by winds and heat while optimizing light absorption. Many species featuring leaf windows are native to Southern Africa.


Functions

The primary function of the translucent windows is to increase the absorption of
radiant energy Radiant may refer to: Computers, software, and video games * Radiant (software), a content management system * GtkRadiant, a level editor created by id Software for their games * Radiant AI, a technology developed by Bethesda Softworks for '' ...
, and thereby the rate of photosynthesis. Epidermal windows are commonly situated at the apex of leaves, allowing light to be captured and utilized even when the plant is almost entirely below the soil surface, minimizing exposure of leaf surface area to
desiccation Desiccation () is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic (attracts and holds water) substance that induces or sustains such a state in its local vicinity in a moderately sealed container. ...
by intense heat. The windows focus and channel diffused light to the green photosynthesizing surface hidden inside the underground part of the plant. An absence of
stoma In botany, a stoma (from Greek ''στόμα'', "mouth", plural "stomata"), also called a stomate (plural "stomates"), is a pore found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange. The pore is bor ...
ta in the translucent tissue prevents water loss. It has been found in the
Lithops ''Lithops'' is a genus of succulent plants in the ice plant family, Aizoaceae. Members of the genus are native to southern Africa. The name is derived from the Ancient Greek words () 'stone' and () 'face', referring to the stone-like appearan ...
species of succulents that leaf window size correlates inversely with habitat
solar irradiance Solar irradiance is the power per unit area ( surface power density) received from the Sun in the form of electromagnetic radiation in the wavelength range of the measuring instrument. Solar irradiance is measured in watts per square metre (W/ ...
; plants growing in regions of high irradiance and low-rainfall have smaller windows than those growing in cloudy, high-rainfall regions. The carnivorous cobra lily (Darlingtonia californica) uses fenestration to confuse insects and increase the effectiveness of its trap.


Species

Genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomencla ...
of plants with numerous species having translucent epidermal windows include: *'' Bulbine'' spp. (B. haworthioides, B. mesembryanthemoides, etc.) *''
Conophytum ''Conophytum'' is a genus of South African and Namibian succulent plants that belong to the family Aizoaceae. The name is derived from the Latin ''conus'' (cone) and Greek ''phytum'' (plant). The plants are also known as knopies (buttons in ...
'' spp. *'' Callisia'' spp. ( ''C. navicularis'', etc.) *'' Fenestraria'' spp. *'' Frithia'' spp. *'' Haworthia'' spp. *''
Haworthiopsis ''Haworthiopsis'' is a genus of succulent plants in the subfamily Asphodeloideae. The genus was previously included in '' Haworthia''. Species in the genus are typically short perennial plants, with leaves often arranged in a rosette and frequ ...
'' spp. ('' H. koelmaniorum'', '' H. tessellata'', etc.) *''
Lithops ''Lithops'' is a genus of succulent plants in the ice plant family, Aizoaceae. Members of the genus are native to southern Africa. The name is derived from the Ancient Greek words () 'stone' and () 'face', referring to the stone-like appearan ...
'' spp. *'' Pleiospilos'' spp. (Questionable) *'' Peperomia'' spp.: notably '' P. columella'' and '' P. nivalis'' *'' Sarracenia'' spp. Several other plant species have epidermal windows: *'' Cephalotus follicularis'' *''
Darlingtonia californica ''Darlingtonia californica'' , also called the California pitcher plant, cobra lily, or cobra plant, is a species of carnivorous plant. It is the sole member of the genus ''Darlingtonia'' in the family Sarraceniaceae. This pitcher plant is nat ...
'' *'' Senecio rowleyanus'' Plants with leaf windows are sometimes known as ''window plants'', though this is also the
common name In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often contrast ...
used to refer to ''Fenestraria rhopalophylla''.


See also

*
Perforate leaf Perforate leaves, sometimes called fenestrate, occur naturally in some species of plants. Holes develop as a leaf grows. The size, shape, and quantity of holes in each leaf can vary greatly depending on the species and can even vary greatly within ...
, leaves which have holes


References

{{Reflist Leaves Plant morphology