Leaf window

Leaf window, also known as epidermal window,[1] and fenestration,[2][3] is a specialized leaf structure consisting of a translucent area through which light can enter the interior surfaces of the leaf where photosynthesis can occur. The translucent structure may include epidermal tissue, and in some succulent plants it consists of several cell layers of parenchyma, which may also function as water-storage tissue.[4] It can appear as a large continuous patch, a variegated or reticulated region, or as numerous small spots. It is found in some succulent plants 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.

For a leaf with window-like holes, see Perforate leaf.
A flowering Fenestraria rhopalophylla, so named due to the translucent leaf window on the tips of its modified leaf.

Functions

The primary function of the translucent windows is to increase the absorption of radiant energy, and thereby the rate of photosynthesis.[5] 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,[6] minimizing exposure of leaf surface area to desiccation by intense heat. The windows focus and channel diffused light to the green photosynthesizing surface hidden inside the underground part of the plant.[1] An absence of stomata in the translucent tissue prevents water loss. It has been found in the Lithops species of succulents that leaf window size correlates inversely with habitat solar irradiance; plants growing in regions of high irradiance and low rainfall have smaller windows than those growing in cloudy, high-rainfall regions.[7]

The carnivorous cobra lily (Darlingtonia californica) uses fenestration to confuse insects and increase the effectiveness of its trap.[8]

Species
The epidermal window of Lithops salicola has a mottled appearance, which acts as camouflage

Genera of plants with numerous species having translucent epidermal windows include:

Several other plant species have epidermal windows:

Plants with leaf windows are sometimes known as window plants, though this is also the common name used to refer to Fenestraria rhopalophylla.

See also

References
  1. Egbert, K. J.; Martin, C. E.; Vogelmann, T. C. (2007-06-19). "The influence of epidermal windows on the light environment within the leaves of six succulents". Journal of Experimental Botany. 59 (7): 1863–1873. doi:10.1093/jxb/ern105. PMID 18436541.
  2. Hickey, M.; King, C. (2001), The Cambridge Illustrated Glossary of Botanical Terms, Cambridge University Press
  3. Beentje, H.; Williamson, J. (2010), The Kew Plant Glossary: an Illustrated Dictionary of Plant Terms, Royal Botanic Gardens, Kew: Kew Publishing
  4. Christensen-Dean, G.A.; Moore, R. (1993), "Development of Chlorenchyma and Window Tissues in Leaves of Peperomia columella", Annals of Botany, 71 (2): 141–146, doi:10.1006/anbo.1993.1018
  5. Egbert, K. (March 2002). "The Influence of Leaf Windows on the Utilization and Absorption of Radiant Energy in Seven Desert Succulents". Photosynthetica. 40: 35–39. doi:10.1023/A:1020129820295. S2CID 23237859.
  6. "Windowed". www.cactus-art.biz. Retrieved 2016-06-10.
  7. Martin, C. E.; Brandmeyer, E. A.; Ross, R. D. (2013-01-01). "Ecophysiological function of leaf 'windows' in Lithops species - 'Living Stones' that grow underground". Plant Biology (Stuttgart). 15 (1): 243–247. doi:10.1111/j.1438-8677.2012.00672.x. ISSN 1438-8677. PMID 23043320.
  8. "Predatory Plant: Lure of the Cobra Lily". KQED Science. 2014-03-03. Retrieved 2016-06-10.
  9. Opel, M.R. (2005), "Leaf Anatomy of Conophytum N. E. Br. (Aizoaceae)", Haseltonia, 11: 27–52, doi:10.2985/1070-0048(2005)11[27:LAOCNE]2.0.CO;2, S2CID 84314908
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