An invigoration regime for Pinusstrobus seeds

Abstract

Samples of a seed lot of eastern white pine (Pinusstrobus L.) from New Brunswick were cold stratified at moisture contents that reached five different levels from 17 to 40% of fresh weight at the end of 4 weeks. Each sample was subsequently tested for germination and mean germination time. Maximum seed germination occurred at a moisture content of about 35%. Three subsamples from another seed lot from the same area were subjected to cold stratification at a slightly suboptimal moisture content (30%) for 0, 2, or 4 weeks. These stratified seeds were subsequently invigorated at 15 °C at the same moisture content for 0, 7, 11, and 16 days. (Vigour is used in this paper to describe a seed lot's mean germination time; increased vigour signifies faster germination.) The seeds were then tested for percent germination and mean germination time. Increasing stratification and invigoration duration influenced percent germination positively, as did their interaction. Drying seeds for 24 h prior to commencing the germination test decreased germination by about 5%. Duration of stratification and invigoration were negatively and highly significantly related to mean germination time in a linear fashion, while their interactive term was nonsignificant and, therefore, not used when analyzing mean germination time. Drying the treated seeds for 24 h increased mean germination time by about 1 day. According to regression estimates, seeds germinated 0.45 ± 0.02 (mean ± SE) day faster per day of invigoration for up to 16 days treatment, while they germinated 1.44 ± 0.06 days faster per week of stratification for up to 4 weeks stratification.