Influence of air humidity and lighting period on growth, vase life and water relations of 14 rose cultivars

Abstract

The influence of three relative air humidities (RH) (75, 83 and 91% RH corresponding to vapour pressure deficits of 550, 390 and 200 Pa, respectively) and two lighting periods (18 and 24 h day −1) on growth, vase life and leaf–water relations was studied in 14 rose cultivars. Air humidity had no effect on the number of flowering shoots while shoot fresh weight decreased by 11% as a mean of all cultivars when RH was raised from 83 to 91%. An increase in the lighting period (LP) enhanced the number of flowering shoots by 12% and fresh weight per shoot by 5%. A rise in air humidity from 75 to 91% RH reduced the vase life by 30% (varying from 12 to 75% in the different cultivars) at 18 h LP and by 44% (varying from 31 to 78% in the different cultivars) at 24 h LP, while an increase in LP reduced vase life by 23 and 38% at 75 and 91% RH, respectively. The magnitude of the responses differed significantly among cultivars. Generally, a close relationship was found between reduction in vase life and rate of water loss of detached leaves from all cultivars. It is concluded that high air humidity and continuous lighting in general should be avoided in the production of greenhouse roses.