Some factors that may influence the invasiveness of Mikania micrantha Kunth ex H.B.K. in Fiji

摘要

A study was undertaken to predict tlie tolerance 'and persistence of Mikania micrantha Kunth ex, H.B.K. seed in the soil seed bank in Viti Levu, Fiji. A iaborator>-controlled ageing test (LCAT) indicated thai M. micrantha seed would likely survivein the soil seed bank for between 1 and 3 years. A second study w as conducted to determine the effect of sodium chloride (NaCl), at concentrations similar to those oc-cuiTinu naturally in the soils of Viti Levu, Fiji, on the uerminalion rate and root development of M micran-thez.Av'crage percent germination in the controls was >93% and this occurred within 5 days of the start of incubalion (30/15deg C +- 1deg C, 12 h photoperiod). Moderate salinity (200mM NaCl) significantly reduced germinaiion to c.60% and high salinity (300mM NaCn down to 6%. Primary root growth was inhibited by low concentrations of NaCl (25mM). However, in such treaiments, seedlings survived by producing a high density, shallow fibrous root system around their siem bases. Thus,seedling establishment could occur e en in moderate levels of NaCl. This implies that M. micrantha can tolerate moderate salinity conditions and may be able to grow in areas where other weed species cannot grow so well. Both studies have identilkd components of the adaptive mechanism emjjloyed by M micrantha in invading agricultural land in Viti Levu. This knowledge on seed longevity and salt tolerance could facilitate the development of management plans of this weed in Fiji.