Relationships between maximum photosynthetic rates and photosynthetic tolerance of low leaf water potentials

Abstract

Comparisons of photosynthesis and stomatal and mesophyll conductance of CO2 at high leaf water potentials were made in four populations of Taraxacum officinale and in drought tolerant and intolerant individuals within cultivars of four crop species. Plants with the highest rates of photosynthesis at high leaf water potentials were least tolerant of drought, in terms of ability to grow in dry soil, or in maintenance of high photosynthetic rates at low leaf water potentials. Differences in photosynthesis at high leaf water potentials resulted from differences in stomatal conductance, whereas differences in photosynthesis at low leaf water potentials resulted from differences in mesophyll conductance.