The Regulatory Role of Polyamines on the Structural and Functional Photoadaptation of the Photosynthetic Apparatus

Abstract

The adaptation of the photosynthetic apparatus to low and high light intensities is a well documented phenomenon, as well in higher plants [1], as in green algae [2]. The organisms respond to shade conditions by increased amounts of chlorophyll at a lowered photosynthetic capacity. Their photosynthetic compensation point is shifted to lower light intensities and the respiratory oxygen uptake decreased. Low light intensities can be mimiced by monochromatic red light in higher plants [3] and by blue light in algae [4]. The photoreceptors responsible for the adaptation to the different light qualities are phytochrome [5] and blue light photoreceptors [6], respectively. Changes in the molecular organization of the photosynthetic apparatus of green algae adapting to low intensities of white light result in an increase of the light harvesting complex, preferentially of photosystem II [7]. The ability of green algae to adapt unexpectedly fast (in about 8h, [8]) to new irradiation conditions demonstrates the high capability of the photosynthetic apparatus to respond to changes in the environmental conditions.