Gibberellin-induced delay of leaf senescence of Alstroemeria cut flowering stems is not caused by an increase in the endogenous cytokinin content

Abstract

The effects of various chemically pure gibberellins and cytokinins on leaf yellowing of Alstroemeria were described. The loss of chlorophyll was measured both in leaves of cut flowering stems and in a model system consisting of detached leaf tips. It was demonstrated that plant growth substances affected chlorophyll loss in both systems to the same extent. Leaf senescence was delayed by various gibberellins and cytokinins. The results demonstrated that some of the gibberellins (GA4 and GA7) are far more effective in delaying chlorophyll loss than GA3, which is commonly used as a postharvest treatment for Alstroemeria cut flowering stems. Immunoassays were used to demonstrate that the effect of gibberellins on leaf yellowing does not involve an increase in the endogenous cytokinin concentrations in the leaves as an intermediate step.