The effects of pinolene-base Vapor Gard (VG) emulsion type film and Kaolin, Surround (WP) particle type film antitranspirants on stomatal behavior, water status, carbon assimilation and transpiration rate of tuberose (Polianthes tuberosa L.) were studied. The plants grown under the irrigation regimes of 100, 80 and 60% of total evapotranspiration (ET) values were investigated to select the most suitable antitranspirant for conserving irrigation water, used in cultivation of tuberose plants in arid regions. Severe water stress, decreased the stomatal frequency and conductance (gs), the leaf water potential (Ψw), the osmotic potential (Ψπ ) and the turgor potential (Ψp), the relative water content (RWC), the chlorophyll content (chl), the carbon assimilation rate (A) and the 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 as 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.
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