Photosynthetic Response of Strawberry Leaves to Changing Temperatures

Photosynthesis is an important process for crop productivity. Net photosynthesis (P-net) of leaves of two strawberry cultivars, grown in the field under plastic tunnels was measured during harvest and related to light intensity, leaf temperature, and leaf age. Light saturation of strawberry leaves was reached at a light intensity of about 1400 mu mol photons m(-2) s(-1). At light saturation, P-net of the leaves increased with increasing temperatures and was highest at about 30 degrees C with 18 and 16 mu mol CO2 m(-2) s(-1) at mid-harvest for 'Marmolda' and 'Darselect' respectively. With further increasing temperatures, P-net decreased. However, at 40 degrees C, P-net was still considerable with about 10 mu mol CO2 m(-2) s(-1) indicating that photosynthesis of strawberry leaves seems to be adapted to hot conditions. Leaf age had a considerable influence on P-net. The youngest fully developed leaf of a plant was compared to 10, 20, and 30 days older leaves at different harvest periods. The older leaves had a 24% or 12% higher P-net than the youngest fully developed leaf for 'Marmolada' and for 'Darselect' respectively. However, the response of P-net to temperature and light intensity was not influenced by leaf age.