... 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 of bright light known as sunflecks. A few plants cope with this by altering the orientation of leaf blades and hence decreasing the amount of light absorbed. * Some shade plants have enlarged root systems to help combat water lost by heat dissipation during sunflecks. * Sunflecks are not far-red enriched and may cause over-excitation of PSII. In the short term, plants may cope by energy redistribution. Light energy is redistributed from PSII to PSI so both photosystems are equally excited. * Prolonged over-excitation of PSII may lead to photoinhibition (reversible damage of photosynthesis). The build ...

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