ISHS Acta Horticulturae 711: V International Symposium on Artificial Lighting in Horticulture
AIR HUMIDITY CONTROL ESSENTIAL FOR ROSE PRODUCTION UNDER CONTINUOUS LIGHTING |
| Authors: | R.I. Pettersen, L.M. Mortensen, R. Moe, H.R. Gislerod |
| Keywords: | air humidity variation, roses, lighting period, powdery mildew, vase life, water loss |
| Abstract:
The effects of diurnal variations in air humidity under continuous lighting period (LP) (24 h day-1 LP) on water loss from detached leaves were studied in two experiments. In experiment one two pot rose cultivars were grown daily periods of 0, 6, 12 and 24 h at 59% (low) combined with 81% (high) relative air humidity (RH) under continuous lighting. Plants grown at 18 h day-1 LP, 81 % RH were used for comparison. Parameters studied were growth, stomatal conductance and water loss under post-production conditions. In the second experiment two cut rose experiment plants were grown at daily periods of 0, 6, 12 and 24 h at 62% combined with 82% relative air humidity (RH) under continuous lighting. In addition, the effect of constant low (62% RH) and constant high (82% RH) was studied at 18 h day-1 lighting period. Parameters studied were vase life, development of powdery mildew and water loss of detached leaves. In experiment one it was found that increasing lighting period from 18 to 24 h day-1 increased the number of flowers by 34 % and decreased the number of days until flowering by 12 % in pot roses. The rate of weight loss of detached leaves from plants grown at constant high RH and continuous lighting was significantly greater than from plant grown at constant low RH or diurnal variation between low and high RH. Measurements of stomatal conductance of plants grown at constant 81 % RH showed that the stomata suffered from lack of closure under post-production conditions and darkness. In experiment two a close relationship was found between the vase life and control of leaf water loss from detached leaves in the different treatments. Reducing the lighting period increased the vase life and decreased the water loss from the leaves both at constant low and constant high air humidity. In continuous light, six hours with low RH considerably increased the vase life as compared with constant high RH in both cultivars. The development of powdery mildew was significantly reduced when the lighting period was increased from 18 to 24 h day-1. | |
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