Target seed moisture content, chilling and priming pretreatments influence germination temperature response inAlnus glutinosaandBetula pubescens

Abstract

The response of common alder [Alnus glutinosa (L.) Gaertn.] and downy birch (Betula pubescens Ehrh.) seeds to germination temperature was examined following chilling and priming. Seeds of two seed lots of each species were subjected to combinations of chilling (4918C) and priming (208C) treatments in fully imbibed (FI) state or a lower target seed moisture content (TMC) level (30% and 35% in alder and birch, respectively). After treatment, the seeds were allowed to germinate for 56 days at constant temperatures of 7.5, 10, 15, 20, 25 or 308C. The response to temperature and pretreatment differed between species, but the effect was consistent in each seed lot within each species. In alder, the TMC seeds germinated well across the full range of temperatures, whereas there was an optimum temperature (22 Á238C) for seeds given the FI pretreatment. Priming had no significant effect on the germination response of the TMC seeds in alder, but priming greatly improved germination in the FI seeds, especially at the lower germination temperatures (optimum 18 Á198C). In contrast, in birch, the TMC seeds germinated better across the full temperature range, but the optimal germination temperature (158C) was the same for all seed pretreatments. Priming improved germination in both the FI and TMC seeds in birch.

Cryopreservation of conditionally dormant orthodox seeds of Betula pendula

“…Seeds that are not exposed to light (or increased oxygen pressure) do not germinate at temperatures lower than 12-15°C. Prechilling (4°C) of moist birch seeds (moisture content 30 or 35%, fresh weight basis) in darkness for 12 weeks increased the germination in comparison with not chilled seeds and seeds chilled in fully imbibed state (De Atrip and O'Reilly 2005;De Atrip et al 2007). Additional priming (20°C) of seeds in fully imbibed state improved germination, which was the highest at 15°C (the range 7.5-30°C was examined) (De Atrip et al 2007).…”

“…Prechilling (4°C) of moist birch seeds (moisture content 30 or 35%, fresh weight basis) in darkness for 12 weeks increased the germination in comparison with not chilled seeds and seeds chilled in fully imbibed state (De Atrip and O'Reilly 2005;De Atrip et al 2007). Additional priming (20°C) of seeds in fully imbibed state improved germination, which was the highest at 15°C (the range 7.5-30°C was examined) (De Atrip et al 2007). Nikolaeva et al (1985) and Heit (1967) emphasized the need for cold stratification (0-5°C) for 1-2 months when germination is carried out at a low temperature in darkness.…”

“…For B. pubescens seeds, dormancy can be released using a target moisture content level of 30-35% (De Atrip and O'Reilly 2005). Priming at 20°C of fully imbibed seeds of this species for 2 days also improved germination after such pretreatment (De Atrip et al 2007). …”

The effect of temperature during cone and seed development on primary dormancy of Scots pine (Pinus sylvestris L.) seeds

“…The seeds have variable primary dormancy depending on seed source, but often benefit from a short moist chill which breaks shallow physiological dormancy, sometimes known as conditional or relative dormancy (Gosling 1984(Gosling , 1988. Unchilled seeds usually germinate over a narrow temperature range that gradually widens as the seeds become non-dormant (De Atrip et al 2007;Gosling et al 2009).…”