"Pollination in Dendrobium, as in several other orchids, induces rapid growth in the width of both the ovary and the column (the organ containing the pollinia and the stigma). The visible effects of that growth do not occur when non-pollinated flowers are exposed to ethylene or after application of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) to the stigma of non-pollinated flowers. However, growth of the ovary and column of pollinated flowers is inhibited by the ethylene antagonist 1-methylcyclopropene (1-MCP) and the ethylene synthesis inhibitor aminooxyacetic acid (AOA). The effects on growth, including column and ovary growth, were similar following the application of an auxin such as 1-naphthylacetic acid (NAA) to the stigma, while studies with ethylene inhibitors showed that NAA acted through ethylene. The known presence in the pollinia of ACC and an auxin-like compound apparently explains the initial growth of the column and ovary in response to pollination"-- Provided by publisher