EFFECTS OF CHANGES IN VENTILATION ON CUCUMBER

Greenhouse temperature and specific humidity decreased after the ventilatiors were opened while water vapour transport by ventilation increased from 1 to 28 g m^-2 min^-1. Transpiration increased from 3 to 12 g m^-2 min^-1, leaf temperature and superficial density of the leaves decreased. Highest leaf temperature was measured around the petiole.

A circular leaf burning occurred around the petiole on leaves in the upper layers of the crop, possibly caused by water deficiency due to the increase of transpiration.

From simulation it was concluded that there is a close relation between water vapour transport and transpiration. Since water vapour transport can be integrated in the ventilation control algorithm it might be possible to counteract too quick changes of transpiration rate and thereby avoid water stress situations and damage of the plants.

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