Characteristics of response of acid phosphatase secreted by the roots of several crops to various conditions in the growth media

Abstract

Five crops (lupin, rice, cabbage, tomato, sugar beet) were grown in phosphorus-sufficient and phosphorus-deficient nutrient solutions. Acid phosphatase was collected for 24 h, and the effects of several soil environmental conditions such as pH, high concentrations of K+, Mg2+, Zn2+, Cu2+, and Al3+, and soil-water extract on its activity were investigated. The activity of acid phosphatase was high at pH 3.5 to 4.5 and decreased with the increase of pH in rice, cabbage, and sugar beet, whereas the activity in the pH ranges from 3.5 to 7.0 was comparatively constant in lupin and tomato. The activity of acid phosphatase did not decrease significantly by high concentrations of K+, Mg2+, Zn2+, and Cu2+in the ranges occurring in the soil solutions of most soils, but decreased slightly by Al3+at the concentration of 0.4 mM. The activity of acid phosphatase secreted by the roots of phosphorus-deficient lupin decreased by the addition of the soil-water extract obtained from a soil with a low phosphorus content, and the decrease was more remarkable at 25°C than at 4°C. Fifty five percent of the acid phosphatase activity compared with that at 0 d, however, still persisted even at 14 d after treatment. Therefore, the activity was considered to be rather stable in reaction to adverse chemical and biological soil conditions for a long period of time. The significance of the response characteristics of acid phosphatase secreted by the plant roots to these soil environmental conditions was discussed. © Taylor & Francis Group, LLC.