Phosphorus and acid phosphatase enzyme activity in leaves of tomato cultivars in relation to zinc supply

Tomato cultivars Blizzard and Liberto were grown hydroponically in a contro lled temperature (C.T.) room for 35 days. The objective was to investigate the relationship between phosphorus (P) concentration and acid phosphatase enzyme [EC.3.1.3.2.] (APE) activity in leaves in relation to zinc (Zn) conc entration in nutrient solution. Zinc was added at concentrations of 0.01, 0 .5, and 5 mg L-1. The 0.01 and 5 mg L-1 Zn treatments led to a significant reduction in dry matter and total chlorophyll content compared with 0.5 mg L-1 for both cultivars. Zinc concentration was considered inadequate in the leaves of plants subjected to 0.01 mg L-1 Zn, while it was at toxic level in those in the 5 mg L-1 Zn treatment according to values stated for tomato plants. Optimal results for all criteria tested in this experiment were fo r plants grown in 0.5 mg L-1 Zn treatment. In the leaves of plants grown at 0.01 mg L-1 Zn, APE concentrations were significantly the lowest and conce ntrations of P were at a toxic level. The APE activity was noticeably highe r in the P-deficient plants of both cultivars grown in the solutions with h igh Zn (5 mg L-1).