Acid phosphatase activity in bean and cowpea plants grown under phosphorus stress

Abstract

The relationship between acid phosphatase activity (APA) and phosphorus (P) stress in two bean genotypes (Phaseolus vulgaris var Tacarigua and var Manuare) and in cowpea (Vigna unguiculata var TUY) are reported in this paper. Sand culture experiments were performed in a highly ventilated greenhouse where plants were drip feed with nutrient solutions with either 1.0 or 0.02 mM P. Acid phosphatase activity was determined in extracts from roots, young (apical) and mature leaves, and in leaf discs and root sections using o‐carboxyphenyl phosphate as substrate. Differences in total dry matter were found to be significant (P = 0.01) only for cowpea. However, reduction in leaf area was significant in both species and varieties. Differences in the P concentration in the dry matter, were large enough to suspect that plants were suffering from a mild P stress. Acid phosphatase activity was above the values reported for these species under P stress, however, APA in these legumes appears not to be inducible by the low P‐concentration level used in this study. A higher APA was found in young as compared to mature leaves, and the expression of APA also showed intraspecific variation. Acid phosphatase activity was related to the age of the leaves and was easily measured in leaf discs, specially for bean. This and the ratio of P concentration between young and mature leaves may be an alternative to absolute P‐status determination in plants.

Notes

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