A study of the regenerative ability of yarrow (Achillea millefolium L.) rhizomes

Abstract

The regenerative ability of yarrow (Achillea millefolium L.) rhizomes was studied in a series of experiments at Lincoln College during 1981-83. Factors considered were: rhizome age, NO₃ concentration, correlative inhibition and the effect of the herbicides glyphosate and 36DCPA.

Complete apex inhibition of auxillary buds was observed in laboratory conditions (25°C; 75% RH). Regenerative ability of the decapitated rhizome fragments was dependent on rhizome length. Fifty-eight per cent, 27% and 17% of bud growth was observed from 120, 80 and 40 mm rhizome fragments respectively. Percentage of actively growing buds and mean bud length also showed the same trend. External NO₃ concentration up to 200 ppm did not result in increasing the mean bud length, although it resulted in increasing the number of growing buds and percentage of actively growing buds. Rhizomes of about one-year-old showed a higher regenerative ability than the very old and young rhizomes.

In field conditions also different age groups of rhizomes showed the same trends. Fragments buried more than 100 mm depth did not produce any shoots. The most suitable depth for regeneration was found to be 25-50 mm irrespective of rhizome age.

Both herbicides were not 100% effective in reducing the potential regeneration in laboratory conditions (2S°C; 75% RH) or greenhouse conditions even at concentrations up to 2.16 kg ai ha⁻¹ glyphosate and 0.5 kg ai ha⁻¹ 36 DCPA. Addition of the surfactant L77 (0.5 v/v) was not effective in increasing the herbicide activity. Severe fragmentation at specific times after herbicide application was recognised as the most important factor in controlling the regenerative ability of rhizomes.