Citrus rootstocks have a strong influence on shoot mineral nutrition and consequently on the adaptation of citrus trees to adverse soil conditions. Since citrus yield is often limited by low P availability, a greenhouse study was carried out to evaluate the effects of P application in the nutrient solution (0.0125; 0.05; 0.2 and 0.8 mmol L-1) on growth and P nutrition of the citrus rootstocks varieties ('Rangpur' lime, 'Swingle' citrumelo, 'Cleopatra' and 'Sunki' mandarin). After 100 days of P treatments, the rootstocks were harvested and further separated into leaves, stem and root system to determine dry weight and P accumulation. Five days before harvesting the experiment, leaves and roots were sampled to determine acid phosphatase activity. The P supply in the nutrient solution improved leaf area, shoot and root dry weigth. P concentration in the leaves and accumulated P were proportional to the P concentration in the nutrient solution. Regardless of P treatment, 'Rangpur' lime had a more vigorous growth and P accumulation, whereas the mandarin varieties 'Cleopatra' and 'Sunki' had lower shoot and root growth. P uptake efficiency was enhanced by P supply in the nutrient solution, and 'Swingle' had the lowest P uptake efficiency. 'Rangpur' lime was the most efficient rootstock in P utilization for biomass production, especially in the shoot. There was variation in acid phosphatase activity in the roots, suggesting that citrus rootstocks differ in the capacity of using soil organic P. Since 'Rangpur' lime tended to have roots with highest P uptake efficiency, most vigorous growth and highest dry weight per unit of P taken up, as well as acid phosphatase activity in the roots, this might be most the suitable rootstock for low-P soils.
nutrient solution; root growth; mineral nutrition; phosphorus uptake
