C₄ Plants and CAM Plants

Abstract

The photosynthetic efficiency of a plant can be defined by the amount of organic matter accumulated under optimal environmental conditions per unit area and time. Ecological conditions of the habitat, to which the plant is adapted, play an important role. This applies particularly to light (see Fig. 14.6). Sun plants, able to utilise the highest natural light fluxes, generally have a particularly high photosynthetic efficiency. However, locations with high light fluxes often experience high temperatures, which stimulate photorespiration (see p. 236), and large water deficits, necessitating a high diffusion resistance for gases at the stomata in order to reduce water loss (see p. 237). The latter is also important in salt-rich locations, where the high osmotic potential (low water potential) of the solution in the soil induces water stress. In general, both conditions prevent optimal utilisation of light by photosynthesis.