Studies on the Origin of Some Hydrolytic Enzymes Associated With the Leaves and Tentacles of Drosera Species and Their Role in Heterotrophic Nutrition

SUMMARY Extracts from the leaves and tentacles of field‐grown plants of Drosera whittakeri, D. binata and D. auriculata had acid protease activity. Several pH optima were associated with some extracts, implying the presence of several proteolytic enzymes but other extracts showed proteinase activity at all acid pH values with no well‐defined pH optima. Only one distinct pH optimum of proteinase activity (pH 2.6) was associated with the leaves and tentacles of axenic cultures of D. binata. Chitinase activity was present in field‐grown plants of D. whittakeri and D. binata. It was not detected in axenic cultures of D. binata nor was it induced when chitin was applied to the tentacles of plants raised in axenic culture. Several of the many bacteria associated with field‐grown plants of D. whittakeri were isolated and found to secrete active extracellular proteinases with acid pH optima. These organisms could account for much of the proteolytic activity associated with extracts of field‐grown plants. Application of a fungicide/antibiotic mixture to the tentacles of non‐sterile plants of D. whittakeri inhibited insect‐enhanced growth. It is concluded that microbial hydrolytic enzymes play an essential role in this process.