Influence of phosphorus limitations on the growth, nutrient partitioning and physiology of mahogany ( Swietenia macrophylla King) seedlings.

The effects of four rates of phosphorus (P) fertilization (0, 0.56, 5.6 and 56.0 mg l⁻¹) in soilless medium on the growth and physiology of mahogany seedlings were examined. The greatest response occurred at the 56 mg l⁻¹ rate, with relatively small differences between other treatments. Biometric parameters increased at the 56 mg l⁻¹ compared to 0 mg l⁻¹ rate except root dry mass. Both the concentration and the total content of P and Kjeldahl nitrogen (N) increased in leaves, stems and roots with P application rate. Foliar concentrations of potassium (K), calcium (Ca), magnesium (Mg), manganese (Mn) and sulfur (S) declined, and boron (B) and copper (Cu) increased with P limitations; zinc (Zn) and iron (Fe) were unaffected. Physiological adaptations of mahogany to P limitations include the preferential allocation of carbon (C) to plant roots, and increases in P utilization efficiency, P acquisition efficiency and the concentration of organic acids in xylem fluid. Root phosphatase activity was not influenced by P fertilization. [ABSTRACT FROM AUTHOR]