An Analysis of the Photosynthesis and Productivity of Vegetative Crops in the United Kingdom

Abstract

The rate of total dry matter production of a vegetative crop, under optimal water and nutrient regimens is related to some leaf and canopy photosynthetic characteristics. Three leaf photosynthetic characteristics are examined in detail: the light utilization efficiency at normal ambient CO₂ and O₂ concentrations, a, the rate of light saturated photosynthesis per unit leaf area, F_max, and the ratio of the rates of photorespira tion and gross photosynthesis. The genetic variability in each of these characteristics is sought from published data on a wide range of C₃ and C₄ plant types. Within C₃ and C₄ plant types there are significant genetic differences only in F_max,, although differences exist between C₃ and C₄ plants in the other two characteristics. The effects of these differences on the rate total dry matter production are estimated, and it is concluded that there is no compelling evidence to indicate that improvements in total dry matter production rates, in the U.K., are likely to result from genetic manipulation of these characteristics in the existing range of plant material.