English

Abstract

Summary Longevity of flowers and overall postharvest performance of plants are the most important quality characteristics in ornamental plants. The omnipresent phytohormone ethylene exerts a central role in both flower development and senescence. Hydrangea is a genus comprising shrubs of high ornamental value and although widely distributed, their tolerance towards ethylene has, besides the use as defoliant prior to cold storage, hardly been investigated. The objective of the current study was to study the effect of ethylene on leaf abscission, flower development and postharvest performance in two commercial Hydrangea cultivars, designated Hm080108 and Hm080109. Ethylene in a concentration of 5 µL L-1 for 7 days served as an effective defoliator in the two investigated Hydrangea cultivars in transition towards dormancy. Hm080108 and Hm080109 dropped 13.5±1.1 and 14.6±1.4 leaves, respectively, in response to this ethylene treatment compared to 5.7±0.5 and 4.6±0.5 leaves, respectively, in the control treatment. Interestingly, defoliation with ethylene had an effect on subsequent flower development; Hm080109 developed significantly more inflorescences compared to non-treated control plants, with 3.3±0.6 and 1.5±0.5 inflorescences per plant, respectively. Vegetative plants of Hm080108 subjected to 2 µL L-1 ethylene responded with a leaf drop of 5.1±0.5 after 12 days of ethylene exposure, i.e., significantly higher than the controls which dropped 1.7±0.5 leaves. Both cultivars subjected to 2 µL L-1 ethylene for three days responded with a significantly higher sepal drop of 18.4±4.4 and 19.5±8.8 for Hm080108 and Hm080109, respectively, compared to no sepal drop in the controls. Collectively, the flower development observed upon defoliation opens up for novel commercial application of ethylene in promoting flowering.