A Comparative Study of the Influence of Drought Stress on Flowering in Urtica Dioica and U. Urens

Abstract
(1) Experiments involving daily transfers of root systems between nutrient solutions and air have been used to examine the effects of desiccation on flowering in Urtica dioica and U. urens. Flowering occurred earlier in U. urens and was maintained at intensities of drought which strongly inhibited reproduction in U. diocia. This difference coincided with lower xylem water potentials and higher mortalities in U. urens and is consistent with plant strategy theories relating life-history and reproduction of frequency of habitat disturbance.