NET PHOTOSYNTHESIS IN MACADAMIA AND PAPAW AND THE POSSIBLE ALLEVIATION OF HEAT STRESS

The rate of net photosynthesis in the subtropical macadamia was at a maximum at temperatures from about 16 to 25°C, but decreased above 26°C and would have reached zero at 41–43°C. When both young and mature leaves were present on the trees the rate of net photosynthesis was slightly higher than in trees with mature leaves only.
At 26°C the rate of net photosynthesis decreased as radiant flux density decreased below 600 Wm^-2 and especially belwo 300 Wm^-2.

In the tropical papaw the rate of net photosynthesis started to decrease above 30°C and was still about half the maximum at 41°C. In this plant net photosynthesis also decreased most rapidly below a radiant flux density of 300 Wm^-2.

Since these orchard trees are often exposed, during the heat of the day, to temperature levels that are obviously adverse for net photosynthesis, the effects of evaporative cooling of orchard trees through intermittent sprinkling, when conditions warrant it, are being studied.

Symposium on Tropical and Subtropical Fruits, XX IHC

P. Allan, J. de Jager

https://doi.org/10.17660/ActaHortic.1979.102.4