How plants have adapted or become acclimated to shade conditons.

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Noreen Mc Quaid

U5400636

TMA 05

Question 2

HOW PLANTS HAVE ADAPTED OR BECOME ACCLIMATED TO SHADE CONDITIONS.

Conditions of shade present low average light intensity for plants, along with a difference in the quality of light (in terms of the numbers of quanta of different wavelengths). Shade light contains more far-red and infra-red quanta and fewer quanta in the range 400 – 680nm.  Additionally, light quality and quantity can vary enormously and rapidly due to the occurrence of sunflecks, (a valuable source of light, yet potentially damaging.)

Adaptation to shade conditions can be determined genetically or be due to acclimation. Obligate shade plants have evolved genetically to exist in permanent shade and cannot acclimate to long-term levels of high light intensity. However there are plants that show an element of phenotypic plasticity and can acclimate to low (and others to high) light intensities.

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  • Shade plants can absorb and utilize low light intensities more efficiently than sun plants; they have a lower light compensation point and achieve net carbon fixation at lower light fluxes. It is their structural and biochemical characteristics which facilitate these properties.

  • At a structural level, shade plants have thinner leaves, with a shallow layer of palisade mesophyll and patchy spongy mesophyll containing more air spaces. They have fewer cells per unit area than sun leaves. Less energy is needed for the construction and maintenance of these thin leaves, making them energy efficient in low light intensities and ...

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