Abstract: This paper is dealing with the effects of the photoperiodic induction of flowering on the activities of four phosphatases (DNase, RNase, PDase, and 5’-NDase) in Pharbitis nil. According to our experimental results, the patterns of changes of activity in these four phosphatases after short-day induction can be put into two cases. One is the case of DNase, which activities are decreased altar short-day treatment both in cotyledons and apices indicating that floral induction leads to dropping of DNA metabolism level Another is the case of the other three phosphatases with a very similar but quite different characteristic from that of DNase. In cotyledons, activities of the three phosphatases after induction are higher than those in the non-induced group. In apices, activities are also higher just after induction, and then drop gradually while activities in the non-induced group rise sharply so that both the two contrast curves show a form of “X”. These changes are evidently interrelated with RNA metabolic regulation in the apices after floral induction.

Key words: Pharbitis nil, Flowering niduction, PDase, 5'-NDase, RNase, Dnase