Photosynthesis inCoffea arabica. I. Effects of Light and Temperature

Abstract

SUMMARY: Photosynthetic rates of coffee plants grown under the full sun and shade were compared. The saturating irradiance of 300 μE₋₁m s₋₁of shade plants shifted to near 600 μE in sungrown plants, but shade plants possessed substantially higher photosynthetic rates. Photosynthetic rates decreased above 25°C, which was apparently due to a decline in the mesophyll conductance, as stomatal conductance remained more or less unchanged between 25° and 35°C. Most of these measurements were made on seedlings in plastic bags. It is concluded that coffee is more suited to high density plantings where mutual shading, resulting in low light intensities and lower leaf temperatures, are likely to produce a favourable environment for efficient photosynthesis and growth.