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Perforate leaf

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Fenestration seen in Monstera deliciosa

Fenestration is a term in botany that refers either to natural holes or to translucent areas (windows) in the flowers or leaves of some species of plants.[1][2]

Holes in plant leaves

The size, shape, and quantity of holes in each leaf can vary greatly depending on the species and can even vary greatly within a given species. Fenestration is caused by sections of leaf ceasing cell growth or by dying during an early stage in the development of the leaf. These deformations that are created earliest in the leaf development end up looking more like slashes whereas those that develop later end up looking more like holes. This trait is found in only one species in Aponogetonaceae and a few genera in Araceae.

It is not fully known what evolutionary purpose fenestration serves, but there are several possibilities. Fenestration could serve the purpose of reducing the chances of leaves tearing in high winds or it could help to maximize the amount of rain that's able to reach the plant's roots. It could help to cool the plant by producing turbulence around the leaf. Another possibility is that fenestration is a defense against herbivory. The holes might make the leaf look less enticing to herbivores.[3]

The term is also used to describe plants with holes in their trunks, such as Platypodium elegans which can be mistaken for a strangler fig.[4]

A flowering Fenestraria rhopalophylla, so named due to the translucent leaf window on the tips of its modified leaf.

Leaf windows

Leaf windows, also called epidermal window, are specialized leaf structures consisting of a translucent area where sunlight can enter into the interior surfaces of the plant's modified leaf where photosynthesis can occur. The translucent structure can appear as a large continuous patch, a variegated or reticulated region, or as numerous small spots. This structural adaptation is found in certain succulent plants native to arid climates, which allow much of the plant to remain beneath the soil surface where it is protected from desiccation of extreme winds and heat while optimizing the absorption of light by increasing the photosynthetic surface area. Many of the known species containing leaf window are native to South Africa and neighbouring countries.Carnivorous plants can also make use of fenestrations by growing traps (highly modified leaves) which use sunlight to lure and/or confuse insects and increase the effectiveness of the trap.[5]

The primary function of the leaf window is to increase the absorption of radiant energy, and there by the rate of photosynthesis.[6] Leaf windows are situated at the apex of leaves, allowing unobstructed sunlight to be captured and utilized even when the plant is buried below the surface of the soil.[7] The absence of stomata in the translucent tissue of the leaf window prevents water loss in the plant. This allows succulents to minimize the exposure of leaf surface area to the outside environment and reduce the risk of desiccation under intense heat. The actual green, photosynthesizing surface is hidden in the underground part of the plant, so that it collects only the diffused light that strikes the windows. Experiments in the Lithops species of succulents, have shown that the size of leaf windows correlates inversely with habitat solar irradiance.[8] Leaf windows of plants growing in regions of high irradiance and low-rainfall were smaller than of those plants which grew in cloudy, high-rainfall regions. It is presumed that the size variation evolved to allow individual plants to set their optimal uptake of sunlight based on its environment.

Species

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

Genus of plants with numerous species having leaf windows include:

Several other plant species have leaf windows:

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

References

  1. ^ The Kew Plant Glossary: an Illustrated Dictionary of Plant Terms, Royal Botanic Gardens, Kew: Kew Publishing, 2010 {{citation}}: Unknown parameter |authors= ignored (help)
  2. ^ The Cambridge Illustrated Glossary of Botanical Terms, Cambridge University Press, 2001 {{citation}}: Unknown parameter |authors= ignored (help)
  3. ^ Muir, Christopher D. "How Did the Swiss Cheese Plant Get Its Holes?" The American Naturalist 181.2 (2013): 273-81.
  4. ^ Richard Condit; Rolando Pérez; Nefertaris Daguerre (8 November 2010). Trees of Panama and Costa Rica. Princeton University Press. pp. 232–. ISBN 978-0-691-14710-9. Retrieved 18 February 2011.
  5. ^ "Predatory Plant: Lure of the Cobra Lily". KQED Science. Retrieved 2016-06-10.
  6. ^ Egbert, K. (March 2002). "The Influence of Leaf Windows on the Utilization and Absorption of Radiant Energy in Seven Desert Succulents". Photosynthetica. doi:10.1023/A:1020129820295. Retrieved June 10, 2016.
  7. ^ "Windowed". www.cactus-art.biz. Retrieved 2016-06-10.
  8. ^ 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, Germany). 15 (1): 243–247. doi:10.1111/j.1438-8677.2012.00672.x. ISSN 1438-8677. PMID 23043320.

Further reading

  • Bown, Deni (2000). Aroids: Plants of the Arum Family [ILLUSTRATED]. Timber Press. ISBN 0-88192-485-7
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