[Growth substances, metabolism of sugars and types of stems in Periploca graeca L].

P. graeca is a species with polymorphous stems: - short upright stems: slow growing and lacking revolutive movement, - long twining stems: fast growing, characterized by revolutive movement (=circumnutation), - long creeping stems: fast growing and diageotropic.The short upright-stemmed type shows evidence of much auxin and cytokinin activity, but no gibberellin activity can be discerned. Among the long-stemmed varieties less auxin and cytokinin activity is found, but the gibberellin activity is greater. No significant difference can be detected between the two long-stemmed varieties.The twining main axis of a young plant has a gibberellin activity which is at a maximum in the third internode from the apex, that is, the internode which carries the curvature responsible for the revolutive movement. The short upright stems are transformed to twining shoots by treatment with gibberellic acid.The stems of P. graeca L. contain sucrose, glucose and fructose in measurable quantities. The long stems have a greater proportion of reducing sugar and a higher invertase activity than the short stems.In the main axis the maximum of invertase activity and the maximum of the level of reducing sugars is in the third internode from the apex. The short stems transformed by a gibberellic acid treatment possess a high invertase activity and a high level of reducing sugars. These results show a relationship between the elongation rate, sugar metabolism and invertase activity.However, it is difficult to establish the relationships between peroxidase activity, auxin level and elongation rate on the basis of our results.