GERMINATION RESPONSE OF ARTEMISIA-TRIDENTATA (ASTERACEAE) TO LIGHT AND CHILL - PATTERNS OF BETWEEN-POPULATION VARIATION

Recently harvested seeds were mostly nondormant at 15°C but required light for full germination. Removal of the pericarp, afterripening in dry storage, and short chill treatments all resulted in a reduction in light requirement. Seed germination response variables were significantly correlated with each other and with mean January temperature at the seed collection site, an index of winter severity. Collections from colder sites were 16-36% dormant in the light at 15°C and nearly 100% light-requiring, while collections from warm desert fringes were nondormant in light and only 50-70% light-requiring. Cold winter collections required up to 98 d to germinate to 50% at 1°C in light, whereas warm winter collections germinated to 50% in as little as 16 d. -from Authors