Journal of Applied Horticulture. 2004: 6(2): 16-22

Effects of Kaolin and Pinolene film-forming polymers on water relations and photosynthetic rate of tuberose (Polianthes tuberosa L.) plants under water deficit conditions

Moftah, A E; Al Humaid, A I

College of Agriculture and Veterinary Medicine, PO Box: 1482 King Saud University, Al-Qassim Branch, Riyadh, Saudi Arabia.

The effects of pinolene-base Vapor Gard (VG) emulsion type film and Kaolin (Surround WP) particle type film antitranspirants on stomatal behaviour, water status, carbon assimilation and transpiration rate of tuberose (Polianthes tuberosa) cv. Double plants, grown under irrigation regimes of 100, 80 and 60% of total evapotranspiration (ET) values, were studied to select the most suitable antitranspirant for conserving irrigation water, with no detrimental effects on growth and production of tuberose plants grown in arid regions. Severe water stress decreased the stomatal frequency and conductance (gs), leaf water potential ( Psi w), osmotic potential ( Psi pi ) and turgor potential ( Psi p), relative water content (RWC), chlorophyll content (chl), carbon assimilation rate (A) and transpiration rate (E). Both types of antitranspirants effectively enhanced the performance and physiological activities of water-stressed plants particularly, at the 80% ET, but they did not compensate for the negative effects caused by the 60% ET treatment. However, the particle type, kaolin, was more effective than the emulsion type, VG, due to its ability to reduce leaf temperature. The increased gs caused by VG and kaolin sprays were accompanied by increased A suggesting that gs might have a limiting effect on A in water-stressed plants. Water use efficiency (WUE) of kaolin-sprayed leaves was significantly higher than that of VG sprayed leaves. However, no significant differences between both antitranspirants on E were recorded. Increased WUE, therefore, could be attributed to a higher A by using kaolin compared with VG sprays. Thus, particle type antitranspirants are more effective in regulating water status, WUE and the photosynthetic activity of tuberose plants in arid regions.