Phosphorus Nutrition of Seedlings of the Waratah, Telopea speciosissima (Sm) R.Br. (Proteaceae)

Seedling waratahs, Telopea speciosissima (Sm.) R.Br., were grown in acid-washed, phosphate-deficient sand in a glasshouse for 14 weeks under ten phosphate regimes from 0 to 31 mg P/kg soil. Root length increased at the lower levels of applied phosphate, but the dry weights of roots did not, indicating thinner roots at low phosphate levels. Adding phosphate above a level of 0.6 mg P/kg soil increased dry matter in shoots and leaf area. Phosphate concentrations in the youngest fully expanded leaf (YFEL) ranged from 0.06% at deficient levels of applied phosphate to 0.4% at the optimal growth level of 3.1mg P / kg soil. Toxicity symptoms were present at phosphate concentrations in shoots of 4.7%. Cluster roots were found with levels of phosphate addition from 0-7.8 mg P/kg soil, and their numbers increased as phosphate was increased from deficient to low levels, and decreased where applied phosphate was adequate for plant growth.