ISHS Acta Horticulturae 420: Ornamental Plant Improvement: Classical and Molecular
FACTORS AFFECTING ETHYLENE SENSITIVITY IN PHALAENOPSIS ORCHID FLOWERS |
| Authors: | R. Porat, A. Borochov, A. H. Halevy |
| Abstract:
Environmental factors and growth conditions affect the response of plants to hormones. In this work we describe physiological, developmental and chemical factors that affect ethylene sensitivity in Phalaenopsis orchid flowers. Pollination-induced senescence is a well known phenomenon in many flowers including orchids. We found that following pollination there was an obvious increase in the flowers sensitivity to ethylene, leading to an enhanced senescence. Changes in the flowers sensitivity to ethylene were also observed during their development from anthesis to senescence: at the day of opening the flowers are rather sensitive to ethylene, and this sensitivity declines during the flowers life span and increases again at senescence. It was suggested that ethylene-induced responses are transduced via signal transduction components. Treating flowers with chemicals that affect the activity of G-proteins and the cytosolic calcium levels resulted in a modification of the response to ethylene: when flowers were treated with cholera toxin and GTP  S, activators of G-proteins, the sensitivity to ethylene increased.
A similar treatment with GDP S that does not activate G-proteins had no effect on the process.
Treating the flowers with calcium ions together with its ionophor A23187, a treatment that was shown to increase the cytosolic calcium level, increased the sensitivity to ethylene.
In contrast, treatments with EGTA, a calcium chelator that reduces the availability of extracellular calcium to the cytosol, decreased the flowers response to ethylene.
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