The effect of cycloheximide and growth regulators on the senescence of cut leaves in Hosta sp. and Zantedeschia aethiopica

The leaves of Zantedeschia and Hosta are used as florist greens in different floral arrangements. The most efficient postharvest treatment for cut foliage is the use of growth regulators, which prolong their vase life by delaying degradative changes occurring in leaves, especially proteolysis. Cycloheximide (CHI) is one of the protein synthesis inhibitors, blocking the enzymes responsible for decreasing membrane integrity, a phenomenon hastening senescence. The aim of this experiment was to evaluate the effects of CHI and benzyladenine (BA) or gibberellic acid (GA₃) on the longevity of cut foliage in hosta (Hosta sp.) cultivars and Ethiopian calla (Zantedeschia aethiopica) and to follow the changes in certain proteolytic processes occurring during senescence. Generally, 24 h conditioning with cycloheximide shortened the longevity of cut calla leaves while having no effect on hosta vase life. In ageing leaves of ‘Minima Glauca’ hosta and calla, the total proteolytic activity increased, including that of cysteine protease. Due to the application of BA or GA₃ in hosta and calla, respectively, this activity was limited. On the contrary, the use of CHI either did not affect the activity of cysteine protease or increased it several-fold relative to the control, in hosta and calla, respectively. Leaves treated with growth regulators had many more soluble proteins and fewer free amino acids, including free proline, than leaves from other treatments. The highest free proline level was determined in calla leaves conditioned with CHI, where it increased 18-fold relative to the initial level.