Abstract: Leaf acid phosphatase activity(APA) is used to diagnose P deficiency in tomato leaves. Results showed that there were significant negative correlations (P<0.01) between the enzyme activity tested with the leaf disc methods and the P concentration in the leaves or whole plants or the dry weight of tomato. Very significant negative correlation (P<0.01) was found in the 15 minutes reaction time with the homogenised leaves method between the enzyme activity and the other 3 elements mentioned above. The assay of the enzyme either with the leaf disc method or with the homogenised leaves method is simple and rapid. Therefore, it can be used to detect P deficiency in the tomato plant. APA is not only affected by P status, plant age and environment, but also by PNPP, pH, temperature and reaction time. So there are many problems to be solved before setting up a critical value for the enzyme activity.

Key words: Tomato, Acid phosphatase, Leaf disc method, Homogenised leaves method