The Effect of Auxins and Ethylene on Leaf Abscission of Ficus Benjamina
Removal of part of the new fully expanded leaf lamina of Ficus benjamina cv. Exotica had no effect on abscission of the petiole, whereas removal of the whole lamina caused abscission within 48 hours. One drop (1 μl of 0.1 mgl-1) of either indole acetic acid (IAA), indole butyric acid (IBA) or naphthalene acetic acid (NAA) applied to the petiole resulted in a delay in its abscission. IAA delayed the abscission for 5 days, whereas IBA and NAA treated petioles started to abscise after 3 days. By 14 days, comparable numbers of the IAA and NAA treated petioles had abscised, however less of the IBA treated petioles had abscised. The time of application of IAA to petioles in relation to removal of the distal part of the lamina also influenced the delay of abscission. No accumulation of ethylene was observed when the removed leaf laminas were held in sealed culture vessels. In contrast, ethylene accumulation occurred in vitro in sealed culture vessels containing shoots of F. benjamina on MS medium supplemented with 0.2 mgl-1 benzylaminopurine (BAP). Sealing and size of culture vessel significantly enhanced the percentage of leaves which abscised. Injection of ethylene into cultures immediately after sealing increased abscission, even when the ethylene inhibitor, silver thiosulphate, was present.
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