Aspects of the Biology of Trientalis Borealis Raf

Abstract

Three species and one subspecies of Trientalis are recognized in North America, but only Trientalis borealis Raf., the northern starflower, occurs in eastern North America. The life cycle consists of three distinct phases each year: shoot development, rhizome growth, and tuber formation. Asexual reproduction by tubers is more important than reproduction by seed. Of the annual dry matter produced, 64.8% is apportioned to asexual reproduction and less than 2% to sexual tissue. Rhizome growth and tuber formation are regulated by photo—period; short days favor tuberization and long days favor rhizome growth. Tuber formation under field conditions began in July, when the photoperiod was about 15 hr. Cool nights and warm days were more favorable for the accumulation of dry matter than warm nights and days. The number of degree—hours accumulated during shoot development of northern and southern populations was similar at sites 200 miles apart on a north—south gradient, but shoot development occurred during a shorter period of time at the northern site. Seedlings of T. borealis have not been found in the field, but relatively high germination rates were achieved under laboratory conditions, Cold treatment increased the percentage germination of trientalis borealis seeds. Ninety days of stratification delayed the period of peak germination and increased the length of time before germination began after the seeds were exposed to room temperatures. The duration of germination and peak period of germination after stratification were about the same for controls and seeds exposed to 30— or 60—day periods of stratification.