ACCUMULATION OF ASCORBIC-ACID IN THE COTYLEDONS OF MORNING GLORY (PHARBITIS-NIL) SEEDLINGS DURING THE INDUCTION OF FLOWERING BY LOW-TEMPERATURE TREATMENT AND THE EFFECT OF PRIOR EXPOSURE TO HIGH-INTENSITY LIGHT

Seedlings of Pharbitis nil strain 'Violet' were cultured at a low temp erature, which induces their flowering even in continuous light, with or without prior exposure to high-intensity light, which enhances the flower-inducing effect of the exposure to low temperature. Analysis by HPLC of extracts of cotyledons showed that the level of an unstable c ompound increased during these treatments, in addition to the increase in levels of phenylpropanoids reported previously. The compound was i dentified as ascorbic acid from the spectroscopic data. The change in the concentration of ascorbic acid at low temperature was correlated w ith the increase in the induction of flowering and the increase in lev els of the phenylpropanoids. The rapid increase in level of ascorbic a cid after exposure to high-intensity light reflected the promotive eff ect of high-intensity light on the induction of flowering at low tempe rature. However, levels of ascorbic acid also increased in seedlings o f P. nil strain 'Kidachi' that were cultured in high-intensity light, a treatment that does not induce flowering in this strain. Thus, ascor bic acid cannot be associated with the induction of flowering by high- intensity light alone. Ascorbic acid increased the rate of formation o f caffeic acid from p-coumaric acid in vitro, a result that suggests t hat ascorbic acid might be involved in the increases in levels of phen ylpropanoids in the seedlings.