Limiting Factors in Photosynthesis- from the Chloroplast to the Plant Canopy

Abstract

The efficiency for solar energy conversion in the most efficient crop like sugar-cane approaches 2 % when expressed on a yearly basis (Varlet-Granchet et al 1978). This yield could seem rather low when compared to the efficiency of the photochemical apparatus which is higher than 30 % under optimal conditions. Despite their low efficiency, plants are still interesting energy converters because they have solved a major problem for solar energy conversion which is the storage of energy under an easily usable form for various purposes (Calvin 1980, this volume). The aim of this paper is to review the main causes of decrease in yield from the chloroplast to the canopy and to look at the possible improvements. This analysis is limited to plants grown under non-limiting conditions for water, temperature and mineral nutrition. The effect of water stress and mineral deficiency is very important in natural ecosystems and is discussed more specifically by Tailing (1980, this volume) for fresh water population and by Divigneaud (1980, this volume) for terrestrial biocenosis.