The Leaf as a Photosynthetic System

Abstract

In Chapter 12, photosynthesis was considered as a function of the “chloroplast” system, and the multiple interactions between photosynthesis and other parts of cell metabolism, e.g. respiratory metabolism, were not discussed. Similarly, many complicated relations between photosynthesis and the structural organisation of higher plants were not taken into account. These physiological aspects of photosynthesis are now considered in this chapter. The leaf is the organ responsible for photosynthesis in cormophytes (see Fig. 29.16). A typical action spectrum of photosynthesis by a leaf is shown in Fig. 14.1; there are significant quantitative differences in comparison with the action spectrum of Chlorella (see Fig. 12.13). The most important difference lies in the scattering of light in the tissue and this is particularly striking in thicker leaves. This leads to a longer optical path and therefore an increased probability of absorption of incident quanta.