A study was conducted to characterize the morphological and physiological responses of four herbaceous perennial species subjected to two subsequent drought cycles.
Lantana camaraL. `New Gold' (lantana), Lobelia cardinalisL. (cardinal flower) , Salvia farinaceaBenth. `Henry Duelberg' (mealy sage), and Scaevola aemulaR. Br. `New Wonder' (fan flower) were subjected to two consecutive 10-day drought cycles. Growth response, leaf gas exchange, and chlorophyll fluorescence were measured during the experiment. The morphology of L. cardinalisand L. camarawas not affected by drought, while S. farinaceahad reductions in plant height and leaf area and S. aemulahad reductions in dry weight. Overall, plant growth and development continued even when substrate water content was reduced to 0.13 mm3mm-3, which indicated a level of substrate water below container capacity was sufficient for greenhouse production of these species. The drought treatments had little effect on the photochemical efficiency (Fv/Fm) of Photosystem II. An increase in minimal fluorescence (Fo) was observed in S. aemulaon the last day of the second cycle. Drought treatment caused increased leaf-level water use efficiency (WUE) at the end of the first cycle in L. cardinalisand S. aemula, but not in L. camaraand S. farinacea. Plants of L. camara, S. farinacea, and S. aemulathat had received drought during both cycles became more water use efficient by the end of the second cycle, but L. cardinalisdid not.