2,4-D AND ALKALOID ACCUMULATION IN PERIWINKLE CELL-SUSPENSIONS

Omission of 2,4-D from culture medium during one subculture of Cathara nthus roseus cells, strain C20, resulted in an increased alkaloid accu mulation, without effect on growth. Alkaloid accumulation, rather than growth, seemed to be more sensitive to 2,4-D. 2,4-D inhibited alkaloi d accumulation essentially during growth phase, but its inhibitory eff ect during this period was partially reversible. As this reversibility was underlined only during the stationary phase, this suggested that this action could be situated upstream in a terpenoid non-specific pat hway. 2,4-D feeding showed that inhibition is weaker and weaker as the alkaloid accumulation period proceeds. Auxin action during this perio d could take place downstream in specific alkaloid pathways. The lower alkaloid accumulation obtained after loganic acid feeding compared to that obtained with secologanin and loganin could indicate that logani c acid methylation should be one of the 2,4-D target(s).