Acid phosphatase as a diagnostic tool

Abstract

There are many reports in which a relationship between P deficiency and acid phosphatase activity (APA) have been found, but, as responses to stress are an integral part of plant growth and metabolism not only enzyme activity but also the appearance of morphological and physiological indicators associated with P stress have to be examined. To this aim, bean, cowpea, pigeonpea, and cotton plants were grown from seed in pots with sand irrigated with nutrient solutions containing 0.01, 1.0, and 0 mM P. Three plants from each we re harvested at different ages and growth and APA determined using i) intact roots, ii) root extracts, and iii) discs from young and mature leaves. APA was measured with p‐Nitrophenylphosphate 5 mM in Na‐acetate buffer 50 mM pH 5 at 30°C. Results showed that NaCl when added to the extracting solution for intact roots, was detrimental to cotton but not to pigeonpea and cowpea and to a lesser extent to bean plants. APA when expressed on a root fresh weight basis decreased with age. Higher activities in intact roots were found for 21‐day‐Old pigeonpea plants grown in 0 and 0.01 mM P. In leaf discs, APA was different among species and P‐treatments, but higher in cowpea leaves. Even though a clear relationship between APA and P‐deficiency was not found, a decrease in leaf area production, increased root/total dry weight ratios and decreased shoot/root ratios were observed. Proper timing for the onset of the P‐stress threshold is apparently crucial for induction of APA in different species.

Notes

This research was partly supported by CDCH‐UCV grant A. 01.31.2980.92.