Effects of environmental factors and ageing on germination of golden crownbeard (Verbesina encelioides) - A wide spread weed of Northern India

Golden crownbeard (Verbesina encelioides), which is abundant along roadsides in Northern India, has started to invade field borders in the South West of Punjab. This study was conducted to find the effect of environmental factors and accelerated ageing on germination of this weed. It germinated over a wide range of temperatures (15/5–35/25°C) with optimum germination at 25/15°C. Light was not a pre-requisite for germination. Germination was completely inhibited at −0.6 MPa. The seeds germinated at 160 mM sodium chloride (13.3%), but no germination was observed at 180 mM NaCl. Germination of seeds was very low at pH less than 5 or more than 8. Germination was 95% when seeds were placed on the soil surface. No emergence was observed when seeds were buried to 6 cm or greater depth. Accelerated ageing of seeds for 20 or more days completely inhibited germination. Results indicate that this weed can emerge in multiple germination flushes. It also has the ability to invade drought affected areas, and can grow in soils that are moderately saline, slightly acidic, or alkaline. However, this weed is not expected to buildup persistent soil seed banks due to rapid loss of viability (time to 50% persistence = 4.11 days) under accelerated ageing.