How plants have adapted or become acclimated to shade.
How plants have adapted or become acclimated to shade. Plants which grow in shady conditions have altered structurally and biochemically in order to cope with the low levels of light and harvest it efficiently. Low level light is rich in far-red light and plants have also adapted to make use of this. Shade plants have also had to make adjustments to cope with sudden high levels of light, for example during sunflecks. Whilst some plants show physiological adaptation, many changes are the result of genetic evolution. * Leaves are thinner with a shallow layer of palisade mesophyll cells and a patchy spongy mesophyll with air spaces (fig 1.). This uses less energy and resources to construct. Many shade plants (such as ferns) do not produce flowers for the same reason. * Shade leaves have more chlorophyll in the antenna systems to feed more energy to the reaction centres. There is also an increase in the number of reaction centres. * Shade light contains more light in the far-red range. The reaction centre of photosystem II (PSII) absorbs more light from the far-red range than photosystem I (PSI); hence there is a greater proportion of PSII to PSI. This is achieved by the presence of wide grana with larger numbers of stacked thylakoids (figure 2.). This enables the photosystems to be excited equally in far-red light. * Plants which grow in shade are often exposed to periods