Drying and storage of prechilled Douglas fir, Pseudotsuga menziesii, seeds

Abstract

Douglas fir, Pseudotsuga menziesii (Mirb.) Franco, seeds exhibit relative dormancy as they do not germinate at suboptimal temperature (15°C), whereas at optimal temperature (20°C) some germination occurred. Thus, germination at 15°C was chosen to estimate dormancy release. In the first experiment, seeds were prechilled at 32% moisture content (MC) for 0-34 weeks at 3°C. Long chilling treatments enhanced germinability and, more markedly, germination speed both at 20°C and at 15°C. Seeds pretreated for the longest periods were then dried to 6.7% MC and stored up to 6 months without any detrimental effect on germination at 15°C. In the second experiment, seeds from a second seedlot were prechilled for 18 weeks and then stored at three different MCs over a period of 17 months. Seeds stored at the lowest MC (6.7%) germinated fastest and to the highest percentage both at 15 and 20°C. In the nursery, seedling emergence tests confirmed results from this experiment. In most cases, comparisons between seeds prechilled at controlled MC before storage and those stratified with the traditional method resulted in better performance of the first ones, both in the laboratory and in the nursery.

Does prolonged stratification of Douglas fir influence the yield of seedlings?

“…Although dormancy need not be the rule for Douglas fir (Müller et al 1999;Dirr, Heuser 2006), seed lots that European nursery operations usually manage show certain signs of dormancy (Martiník, Palátová 2012). From the available references and the current practice (e.g.…”

Germination and emergence response of specific Douglas fir seed lot to different temperatures and prechilling duration

“…In the case of sowing dormant seeds in spring, an adequate pre-sowing treatment is also a vital condition of success (Sorensen 1991). In general, there are large differences in dormancy with respect to the origin of Douglas fir seed lots (Müller et al 1999;Martiník Palá-tová 2012). According to Heit (1968) stratification is necessary only for Douglas fir var.…”

“…Germination capacity of these seeds without stratification was considerably limited. The manifestation of dormancy -reduced germination of non-stratified seeds at sub-optimum temperatures (Bewley, Black 1994;Müller et al 1999;Gosling et al 2003) -is also apparent from the germination outcome of non-stratified seeds in the conditions of both phytotrons. At temperatures of 11 and 15°C, the non-stratified seeds germinated either not at all or only minimally.…”

“…One of the critical points in artifi cial regeneration of Douglas-fi r is a small yield of seedlings in nursery practice of the Czech Republic. From many aspects which infl uence the yield of Douglas fi r seedlings the presowing treatment seems to be important because the seeds exhibit dormancy (Heit 1968;Gosling, Peace 1990;Müller et al 1999).…”

“…One of the critical points in artifi cial regeneration of Douglas-fi r is a small yield of seedlings in nursery practice of the Czech Republic. From many aspects which infl uence the yield of Douglas fi r seedlings the presowing treatment seems to be important because the seeds exhibit dormancy (Heit 1968;Gosling, Peace 1990;Müller et al 1999).Cold stratifi cation of seeds has a favourable eff ect on subsequent germination and shows an increase in total germination capacity, increased germination rate and extended range of temperatures at which the seeds germinate (Gosling 1988). Th e main prerequisite for successful stratifi cation is its suffi cient duration.…”