POLYAMINE LEVELS DURING THE ONSET OF CAM IN OPUNTIA-F-INDICA (MILLER)

Polyamines have been related to the ''Crassulacean Acid Metabolism'' ( CAM) in higher plants. Such relationship was however observed in plant s where CAM activity is inducible by external factors. Results present ed here indicate that, in Opuntia F. indica, cladodes where onset of C AM is dependent on internal conditions, i.e. leaf age, the concentrati on of putrescine increases in parallel to the acidity of the cytoplasm . The parallel increase of putrescine concentration and acidity (malic acid concentration) can be best evaluated during the onset of CAM (yo ung cladodes), while such correlation is not observed in mature cladod es where CAM is already in it's full function. Spermidine and spermine show no correlation with CAM activity neither during the onset of CAM nor during it's full function. However, spermidine levels correlate n egatively to CAM activity when cladodes attain > 30 days of age. The r esults suggest that putrescine in free form could possibly counteract the increase of cellular acidity during onset of CAM in Opuntia F. ind ica; the possible roles of spermidine are discussed.