High Temperature Effects on Leaf Resistance, Leaf Water Potential, and Photosynthesis of Non-bearing Prune Trees1

in Journal of the American Society for Horticultural Science
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  • 1 Department of Pomology, University of California, Davis, CA 95616


The effects of ambient temperatures between 15° and 43°C were determined on net photosynthesis of ‘French’ prune (Prunus domestica L. cv. Agen) trees maintained under a non-limiting soil water supply. The temperature optimum for photosynthesis was about 30° and net CO2 assimilation decreased rapidly above 35° even when water vapor pressure differences (VPD) were only 5 to 10 mb. Leaf resistance (r1) remained very low (2 to 3 sec cm-1) although leaf temperature reached 47° and the leaf water potential (ψ) decreased to -25 bars. Thus, non-stomatal photosynthetic inhibition was responsible for the 80% decline in net CO2 assimilation. Canopy wetting prevented the decline in net CO2 assimilation by reducing leaf temperature 8° (vs. control) and maintaining the ψ 14 bars higher than the non-misted control.

Contributor Notes

Received for publication July 3, 1980.

The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact.

Present address: Department of Citriculture, Hebrew University of Jerusalem, Faculty of Agriculture, Rehovot, Israel.

Present address: Division of Fruit Breeding and Genetics, The Volcani Center, Bet-Dagan, Israel.

Department of Botany, University of California, Davis.