Landscapes in the desert Southwest must be water efficient and utilize drought tolerant plants. Therefore, plants with landscape potential must be evaluated for their level of drought tolerance and drought tolerance mechanisms. Drought tolerance, for some plant species, may be related to the plants ability to produce ethylene as a mechanism for defoliation, thus reducing water use. Cassia corymbosa has potential as a woody shrub for southwestern landscapes because of its dark green foliage and bright yellow flowers. Studies were conducted to determine the effect of leaf dehydration and drought stress on ethylene production in Cassia. Leaf dehydration was examined by excising leaves and placing them at 20, 25, or 30 °C. The time course of ethylene production depended on the temperature (rate of dehydration), but the peak occurred at 18% to 25% fresh weight loss, regardless of dehydration temperature. The effect of irrigation rate was determined by supplying plants with 0%, 40%, 60% and 100% of the daily water consumption (WC) based on pot capacity. Ethylene production depended on irrigation rate. Plants irrigated at 100% of daily WC were not stressed and did not produce ethylene. Irrigation at 60% of daily WC induced peak ethylene production 72 hours after treatment with decreased production as at longer times. Irrigation at 40% or 0% of the daily WC did not induce ethylene production because of the rapid dehydration. Drought-induced ethylene production in Cassia corymbosa appears to be closely related to the rate of dehydration and may provide a drought tolerance mechanism.
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