THE INFLUENCE OF DIFFERENT CONSTANT AND FLUCTUATING WATER VAPOUR PRESSURE GRADIENTS ON MORPHOGENESIS
A drop in the relative humidity from 90% to 60% for four hours either before or after sunrise did not give any significant differences. However, there was a tendency for a slightly increased shoot elongation when the relative humidity drop occurred before sunrise compared to after sunrise.
Aeschynanthus responded in several ways contrary to the other plant species. There was e. g. a tendency for a decreased shoot elongation at 90% relative humidity, and a significantly increased one, when the relative humidity drop was in the day period. The water consumption was 111% higher at 60% relative humidity than at 90%. A drop in the relative humidity after sunrise increased the water consumption by 7% compared with a drop before sunrise.