Physiological Response of Periwinkle Plants (Catharanthus roseus L.) to Tryptophan and Putrescine

A pot experiment was conducted in the screen of the National Research Centre during two successive seasons to study the response of periwinkle plants to foliar spray with tryptophan or putrescine at the concentrations 10 M, 10 M or 10 M. The obtained data indicated that exogenous application of tryptophan or putrescine on periwinkle transplants considerably increased plant growth at successive developmental stages. The effect was more pronounced with 10 M tryptophan or putrescine. Photosynthetic pigments (chlorophyll a, chlorophyll b and carotenoids), soluble and total insoluble sugars, total proteins and total alkaloids in the leaves of periwinkle plants were increased as a result of application of tryptophan or putrescine, more so with 10 M each. Tryptophan at 10 or 10 M increased gibberellic acid (GA3), IAA and ABA contents, while low concentration (10 M) of tryptophan decreased their endogenous levels. Tryptophan at 10 M or 10 M decreased cytokinins, while application of tryptophan at 10 M increase the endogenous cytokinins. Foliar application of putrescine at used concentrations caused obvious increases in the quantitative amounts of endogenous GA3, IAA, cytokinins and ABA.