Growth, physiological and flowering responses of Xanthostemon chrysanthus (F. Muell.) Benth. to paclobutrazol and potassium nitrate / Ahmad Nazaruddin Mohd Roseli

Xanthostemon chrysanthus (F. Muell.) Benth. or golden penda (locally known as jambu kuning) is gaining its popularity in Malaysian landscape. However, under local climatic condition, the flowering of X. chrysanthus is very erratic and inconsistent. An investigation on the growth, physiology, flowering and identification of a suitable practice to induce flowering of this species was carried out. Based on the Biologishe Bundesanstalt, Bundessortenamt and Chemical Industry scale, nine principal growth stages, i.e. bud development (stage 0), leaf development on tree branches (stage 1), formation of side shoots (stage 2), shoot elongation (stage 3), inflorescence emergence (stage 5), flowering (stage 6), fruit development (stage 7), maturity or ripening of fruit and seed (stage 8) and fruit senescence (stage 9) were determined in X. chrysanthus. Vegetative and reproductive stages of this species were completed within 198 and 176 days, respectively. Xanthostemon chrysanthus planted in loamy sandy soil at two selected urban sites in Kuala Lumpur, i.e. Metropolitan Batu Park (MBP) and Pusat Bandar Manjalara (PBM) showed that trees at MBP, which is a recreation park with bigger planting area, had better growth performance than those trees at road median at PBM. Significant higher coarse sand content in soil of PBM influenced the water holding capacity, causing significantly lower growth responses, especially the relative growth rate of canopy diameter and leaf area index. Physiologically, higher photosynthetic rate, transpiration rate and stomatal conductance were recorded during rainy season with vegetative branches as compared to reproductive branches. Profuse flowering was observed with some trees at MBP in certain times while none of the trees flowered at some other times…