EFFECT OF NIGHT HUMIDITY ON THE VEGETATIVE GROWTH AND THE MINERAL-COMPOSITION OF TOMATO AND STRAWBERRY PLANTS

Conditions of low night humidity (50-55%) and high night humidity (90- 95%) were imposed on tomato plants (Lycopersicon esculentum Mill. cv. Young-Kwang) for 30 days, and on strawberry plants (Fragaria grandiflo ra Ehrh. cv. Bogyo) for 40 days. Shoot dry weight and leaf area in tom ato plants increased with high night humidity whereas the strawberry p lants did not show any such increases. The concentrations of five majo r nutrients (N, P, K, Ca and Mg) were reduced in tomato plants under h igh night humidity, with the calcium content in younger leaves being t he most severely affected. For the strawberry plants, however, high ni ght humidity tended to increase the concentrations of major nutrients, including calcium in the younger leaves. Possible reasons for the dif ferences in response of these two species to night humidity are discus sed. (C) 1997 Elsevier Science B.V.