Cold treatments enhance responsiveness to gibberellin in stock (Matthiola incana (L.) R. Br.)

Endogenous GAs have been suggested as regulators of stem elongation and flo wering of cold-requiring plants. Here, the relationship between temperature conditions and responsiveness to GA(4) on stem elongation and flowering of stock (Matthiola incana) was investigated. The optimum temperature for ind uction of flower bud initiation was 10 degreesC, acid the minimum duration was 20 d in the late flowering cv. Banrei; the type of cold treatment effec t on flowering was classified as a "direct effect". Stem elongation was mar kedly promoted by cold treatment regardless of flower bud initiation. The c old treatment amplified the stem elongation response to GA(4). The GA(4) le vel necessary for flower bud initiation was lower in the 10 degreesC treatm ent than in the 15 degreesC treatment, and it became lower at longer durati ons of cold treatment. These results indicate that the cold treatments enha nce responsiveness to GA(4) not only in the stem elongation process but als o in the flower bud initiation process and that the development of responsi veness to GA(4) may correlate with the temperature and duration of cold tre atment.