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 1. Present
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.
Changes in root morphology and acid phosphatase activity (APA) were followed during the developent of P-deficiency in tomato plants grown for 7, 14, and 21 days in 0.16 P well aereated nutrient solutions, followed by a period of sufficiency (recovery) in 1 mM P. Plants were harvested weekly for APA, dry weight, and P concentration in roots, stems and leaves, and every 2 weeks for root morphology determinations. APA was highly correlated to development and recovery from P stress. Mixmium values were attained during growth under deficiency and decreased to that of the control plants after a period of recovery in 1 mM P nutrient solutions. Total root weight and average root diameter decreased under P-stress and root surface area per unit dry weight increased. Efficiency of P utilization (g dry weight/mg absorbed P) was much higher at the end of the stress period but approached that of the controls as P-supply was restored to sufficiency levels. The implications of these results in developing rapid and reliable screening technigues to detect successful plant performance under P-stress is discussed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.