THE INFLUENCE OF DIFFERENT CONSTANT AND FLUCTUATING WATER VAPOUR PRESSURE GRADIENTS ON MORPHOGENESIS

H.K. Schüssler
Various constant and fluctuating air humidity levels were shown to affect shoot elongation and anthesis of several plant species i. e. Aeschynanthus hybr., Begonia x elatior, Chrysanthemum indicum hybr., Euphorbia pulcherrima, Impatiens New Guinea hybr., Kalanchoe blossfeldiana, Lycopersicon lycopersicum and Saintpaulia ionantha. The plants were grown at a constant air temperature of 20°C ± 0.1°. At 60% relative humidity (vapour pressure gradient 0.94 kPa), shoot elongation that of most of the plant species, decreased compared with at 90% relative humidity (vapour pressure gradient 0.24 kPa). There was also a noticeable difference in the appearance of the plants, those from the treatment with low relative humidity being shorter and more compact. Fresh weight decreased, but the dry weight percentage increased. For Saintpaulia, the number of days to anthesis increased at 60% relative humidity.

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.

Schüssler, H.K. (1992). THE INFLUENCE OF DIFFERENT CONSTANT AND FLUCTUATING WATER VAPOUR PRESSURE GRADIENTS ON MORPHOGENESIS. Acta Hortic. 327, 105-110
DOI: 10.17660/ActaHortic.1992.327.14
https://doi.org/10.17660/ActaHortic.1992.327.14