Vol. 71 No: 5

Title:
Night Water Consumption by Rose Plants

Authors:
G. ASSAF and N. ZIESLIN

pp: 673-678

Abstract:
Night water consumption of rockwool-grown rose plants was measured during winter months in two separate greenhouses where a night temperature of 17° ± 1°C was maintained. The air relative humidity in one of the greenhouses (A) was controlled during the night hours by frequent fan operation, whereas the second greenhouse (B) was equipped with a dehumidifier and a thermal screen. The average heat transfer coefficient and the energy consumption for maintenance of the desired temperature in greenhouse B were lower than in greenhouse A and the average water consumption of rose plants in greenhouse B was also lower by 57% than in greenhouse A. A significant correlation (r² = 0.94) was found between the heat load of the greenhouse and the night water loss from the plants. Stomata were open and transpiration occurred during the night heating period. Cessation of heating was accompanied by stomatal closure and decreased transpiration. The difference in water loss between the plants in the two greenhouses was attributed to a difference in convective heat flux through the plant canopy from the heating elements near the ground to the cold roof. The possibility that the night transpiration of rose plants and probably [...] other [...] species might be affected by thermal convection is proposed.

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