WATER-USE, WATER-USE EFFICIENCY AND GROWTH ANALYSIS OF SELECTED WOODY ORNAMENTAL SPECIES UNDER A NONLIMITING WATER REGIME

Selected woody ornamental species were grown in a glasshouse under a non-limiting irrigation regime. Relative growth rate (RGR), net assimilation rate (NAR), leaf area ratio (LAR), whole plant transpiration (T), evapotranspiration (ET) and water-use efficiency (WUE) were determined during a 73 day period. Covering the container medium with polyethylene reduced evaporative losses from 13% to 88%, depending on plant species, without affecting growth. The greatest reduction in evaporation occurred in plants with open canopies and low T rates. The shrub/tree species Lagerstroemia indica had the highest NAR and RGR, while the prostrate (plagiotropic) ground covers Trachelospermum asiaticum and Jasminum floridum and the orthotropic shrub/tree species Ligustrum japonicum had the lowest NAR and RGR. Leaf area ratio was greatest in Ligustrum and Pittosporum tobira. Water consumption, leaf area and root:shoot ratio were greatest in Lagerstroemia. Sophora secundiflora, which is adapted to more xeric conditions, had the highest T and lowest WUE. The highest WUE was found in Lagerstroemia, Raphiolepis and Pittosporum.