THE INFLUENCE OF THERMAL SCREENING AND MOISTURE GAP ON THE TRANSPIRATION OF GLASSHOUSE TOMATOES DURING THE NIGHT.

From research with glasshouse tomatoes in which comparisons were made between glasshouse compartments with and without thermal screens, it was shown that transpiration decreased significantly through thermal screening. The decrease in transpiration became greater in the course of the growing period. The reduction of transpiration under thermal screen depends on the level of transpiration. At a level of 0.45²1 m^-2 night^-1 and 0.10 1 m^-2 night^-1 the reduction by screening was 25 and 60% respectively.

The difference in transpiration between compartments with and without thermal screen disappeared after a small opening was made. Obviously under these conditions a moisture ventilation of 15–20 cm in the compartments with thermal screens was enough to maintain transpiration at levels similar to compartments where thermal screens were omitted.

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