Germination of Goldenweed Seed

Abstract

Large, well-filled seed of Drummond's goldenweed (Isocoma Drummondii (T. & G.) Greene) germinated in excess of 80% over a broad range of continuous temperatures (10 to 25° C). Germination of Drummond's and common goldenweed (Isocoma coronopifolia (Gray) Greene) seed was about 20% higher under alternating than constant temperature regimes, and 20 to 30% lower in absence of light. Germination and early seedling growth were reduced by -4 and -2 bars simulated moisture stress, respectively. Germination and early seedling vigor were relatively tolerant of extremes of pH, but NaCl concentrations of 5,000 ppm or higher reduced germination. Drummond's goldenweed seed viability decreased significantly after 200 days storage at room conditions, and no achenes of either species germinated after storage for 15 months. Seed collected from robust plants growing on deep, fertile soil had a higher percent germination than those of plants growing under less favorable conditions, although unimbibed achene weight did not differ. No seed dormancy mechanisms were observed. Initial seedling establishment apparently depends primarily on the occurrence of adequate rainfall in late winter and early spring.