GROWTH CHARACTERISTICS OF THREE EUCALYPTUS CLONAL HYBRIDS IN RESPONSE TO DROUGHT STRESS: THE UNDERLYING PHYSIOLOGY By

ii Previous research by Drew et al. (2009) on a SAPPI dendrometer trial, in northern KwaZulu-Natal, South Africa, yielded growth results for two Eucalyptus grandis clones (termed E. grandis x urophylla (GU) and E. grandis x camaldulensis (GC)). The GU clone was found to have a greater diameter than the GC clone, and further research has demonstrated that age, not environmental conditions, is the major determinant of tree growth for the GU and GC clone. The clones also showed different patterns of growth response following a rainfall event. In current study, young plants of three Eucalyptus grandis clones (two GU clones (GUA and GUW) and one GC clone) were grown in 80 L planting bags for 18 months at UKZN, Westville, South Africa. The experiments for this study entailed subjecting the three clones to three watering regimes. The trial was conducted using a randomised complete block (RCB) with a 3 3 factorial design (i.e. 9 treatments with 12 replicate plants in each treatment). The three watering regimes were monitored daily with a soil moisture probe an