Effects of Low Temperature, Seed Source, and Seed Age on Germination of Chamaecyparis lawsoniana

1990

1 Abb., 4 Tab., 21 Lit. Ang.

Unselbständiges Werk

9716

200088890

Seeds of Port Orford cedar (Chamaecyparis lawsoniana (A. Murr.) Parl.) were collected throughout its natural range. Air-dried seeds were stored in glass bottles at -15C. Seeds from 35 sources were germinated fresh, after 3.6 and 10.7-11.7 years of storage. The oldest seeds were germinated on a temperature-gradient bar at ca. 5-20C. Initial germination capacity averaged 19-58% for nine collection areas and did not decrease with storage, germination in darkness, or a ca. 40-day period at suboptimal temperatures. Median rates of germination (1/days to 50% germination) decreased in darkness and at suboptimal temperatures. There was no consistent relationship between rate and capacity, nor evidence of a stratification effect. Estimates of the lower temperature limit for germination ranged from 9.6 to 14.0C (mean 12.6C). A temperature of 14.5-17.0C (mean 15.9C) was required to germinate half of the potentially germinable seeds. Seeds from coastal and low-elevation sites germinated fastest and responded most to rising temperatures. A high threshold for the lower temperature limit for germination may compensate for lack of dormancy and by causing late germination, contribute to the tree's limited distribution.