Water Relations of Hibiscus following Pruning or Chemical Growth Regulation

in Journal of the American Society for Horticultural Science
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  • 1 Texas A&M University, College Station, TX 77843

Growth of potted hibiscus (Hibiscus rosa-sinensis L.) was limited either by pruning or by a soil drench of `uniconazole at 3.0 mg a.i. per pot. Both treatments changed the water use of hibiscus. Five days after treatment with uniconazole, plants showed reduced water use, an effect that became more pronounced with time. Water use of pruned plants was reduced immediately after pruning, but soon returned to the level of the control due to the rapid regeneration of leaf area. Pruned or chemically treated plants used 6% and 33% less water, respectively, than the control. Chemically treated plants had a smaller leaf area, and individual leaves had lower stomatal density, conductance, and transpiration rate than control plants. Under well-watered conditions, the sap flow rate in the main trunk of control or pruned plants was 120 to 160 g·h-1·m-2, nearly three times higher than the 40 to 70 g·h-1·m-2 measured in chemically treated plants. Liquid flow conductance through the main trunk or stem was slightly higher in chemically treated plants due to higher values of leaf water potential for a given sap flow rate. The capacitance per unit volume of individual leaves appeared to be lower in chemically treated than in control plants. There was also a trend toward lower water-use efficiency in uniconazole-treated plants. Chemical name used: (E)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-l-yl)-1-penten-3-ol (uniconazole).

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