High floral bud abscission and lack of open flower abscission in Dendrobium cv. Miss Teen: rapid reduction of ethylene sensitivity in the abscission zone
Kanokpon Bunya-atichart A , Saichol Ketsa A C and Wouter G. van Doorn BA Department of Horticulture, Faculty of Agriculture, Kasetsart University, Chatuchak, Bangkok 10900, Thailand.
B Wageningen University and Research Centre, PO Box 17, 6700 AA Wageningen, The Netherlands.
C Corresponding author. Email: agrsck@ku.ac.th
Functional Plant Biology 33(6) 539-546 https://doi.org/10.1071/FP05200
Submitted: 11 August 2005 Accepted: 9 March 2006 Published: 1 June 2006
Abstract
We studied the abscission of floral buds and open flowers in cut Dendrobium inflorescences. Abscission of floral buds was high and sensitive to ethylene in all cultivars studied. Many open flowers abscised in most cultivars, but cv. Willie exhibited only small amount of floral fall and cv. Miss Teen none. Applied ethylene (0.4 μL L–1 for 24 h at 27°C) greatly hastened abscission of open flowers in most cultivars, but had only a small effect in cv. Willie and no effect in cv. Miss Teen. Flower fall, if it occurred, was completely inhibited by 1-methylcyclopropene (1-MCP), showing that it was regulated by endogenous ethylene. Ethylene production from the abscission zones was low in all cultivars studied. In cv. Miss Teen the abscission zone changed from highly ethylene sensitive to completely insensitive in ~30 h, coinciding with floral opening. Removal of the floral buds somewhat reduced abscission in open flowers, but the lack of open flower abscission in cv. Miss Teen could not be explained by higher bud fall. The ovary did not grow in the (unpollinated) flowers, showing that lack of abscission in cvv. Willie and Miss Teen was not due to parthenocarpy. Flower removal in cv. Miss Teen had no effect on ethylene sensitivity of the abscission of the remaining pedicel. However, removal of the distal 2 cm of the 3-cm-long pedicels dramatically increased ethylene sensitivity. This suggests that the pedicel is important for the low ethylene insensitivity of abscission, in this cultivar. It is concluded that the abscission zones in the cvv. Willie and Miss Teen, in contrast with the other cultivars investigated, became rapidly insensitive to ethylene at the time of flower opening. At least part of the ethylene sensitivity in Miss Teen seems to be due to a factor in the pedicel.
Keywords: Dendrobium, ethylene production, ethylene sensitivity, flower abscission.
Acknowledgments
The authors acknowledge the contributions of the Thailand Research Fund and of the Postgraduate Education and Research Development Project in Postharvest Technology.
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