Morphological Response of Eucalyptus Seedlings to Phosphorus

Eucalyptus has attracted attention from global development researchers and environmentalists due to its desirable trait of fast growth and commercial values as wood and pharmaceutical sources. To better grow Eucalyptus and figure out its growing and survival ability in phosphorus (P) limiting conditions, Eucalyptus citriodora and E. dunnii were selected and grown hydroponically in a greenhouse at six P concentrations of 0, 0.01, 0.1, 0.5, 1 and 2 mM for two months. Phosphorus concentration in solution affected plant tissue P content (r= 0.9591, 0.9658; P value= 0.0025, 0.0017, for E. citriodora and dunnii). Phosphorus use efficiency at low P concentration (0.1 mM) was 13 g/mM and 19 g/mM for E. citriodora and dunniii. While at regular (0.5mM) and high (1mM) P concentration, P use efficiency reduced to 2.34 , 1.56 and 5.7, 2.66 g/mM. Leaf area, stem diameter at the base, height, number of nodes, internodes length, shoot and root biomass, showed similar response at 0 and 0.01 mM levels (extremely low P) and seedlings were stunt. Optimum growth occurred at 0.1 mM (Low P), 0.5 mM (regular P), 1 mM (high P) without significant differences. The average of leaf area, stem diameter at the base, height, number of nodes, internodes length, shoot and root biomass for E. citriodora were 220.1875 m², 3.4325mm, 24.6250cm, 15.8750, 1.3704cm, 1.7288g, 0.6375g at 1mM. E. dunnii showed the same trend. However, at highest P level (2 mM), Eucalyptus growth was significantly reduced due to toxicity and inhibition of other nutrient, especially micronutrient uptake. Eucalyptus could use P efficiently and low P at 0.1 mM should be sufficient to grow Eucalyptus seedlings.