Seed moisture content during chilling and heat stress effects after chilling on the germination of common alder and downy birch seeds

Abstract

The effects of seed moisture content (MC) and heat treatment on the germination response of common alder (Alnus glutinosa) and downy birch (Betula pubescens) seeds were examined. Seeds of each species were adjusted to MC of 7% to 50% MC, then chilled for up to 36 weeks, after which they were allowed to germinate at 15°C with 8 hours lighting per day or 20 (dark)/ 30°C (light). Seed lot effects were evident, but treatment effects were consistent in each lot and species. The response to moist chilling treatments was larger at 15°C than at 20/30°C. Chilling had no effect on germination unless seed MC was >15%, but it was low also at 20% MC. The highest germination was achieved following 24-36 weeks chilling at the optimum or target MC (TMC) levels of about 30% in alder and 35% in birch. In a separate experiment, seeds were fully imbibed (FI) (~50% MC; standard method used in operational practice) or adjusted to TMC levels, after which some seeds of each treatment group were chilled to release dormancy. Following this, the seeds were dried back to TMC levels and then subjected to 60°C for up to 4 hours after which they were allowed germinate under the same conditions described above. Heat treatment damaged the prechilled FI seeds, but no damage occurred to the non-chilled seeds. However, heat stress stimulated germination in the non-chilled FI seeds of both species and the TMC seeds of alder.

Effect of soil moisture during stratification on dormancy release in seeds of five common weed species

“…These results agree with those of previous research on trees that seed moisture content must reach a critical level for dormancy breakage to occur during cold stratification (e.g. Jensen, ; O'Reilly & Atrip, ). In our study, germination of A. retroflexus , C. album and C. hybridum seeds increased and then decreased as soil moisture content increased, suggesting that a certain seed moisture content is necessary for dormancy breakage during cold stratification.…”

“…Generally, the effective temperatures for cold stratification are between 1 and 10°C with speed of dormancy breakage being highest at 2–5°C (Stokes, ). The optimum seed moisture content for dormancy breakage during cold stratification has been determined for a relatively few species, including the trees Alnus glutinosa (L.) Gaertn., 30% (O'Reilly & Atrip, ); Betula pubescens Ehrh., 35% (O'Reilly & Atrip, ); Picea glauca (Moench) Voss., ≥25% (Downie et al ., ); and Picea sitchensis (Bong.) Carrière., 25% and 30% (Gosling & Rigg, ).…”

Food storage in a changing world: implications of climate change for food-caching species

“…In general, some moisture is required to facilitate germination but the optimum water content varies across species [111]. Soaking seeds is a common commercial method used to "prime" seeds for germination, leading to a higher percentage of germination for many species [2,118].…”

Desiccation, Moisture Content and Germination of Zostera marina L. Seed

“…After each exposure time, 100 seeds were examined from each of three replicate groups from each treatment for germination rate using an actual germination method (described above). Similarly, 100 seeds were examined from each of three replicate groups from each treatment for MC using the formula: where w 1 was the weight of the seeds after desiccation exposure and w 2 was the weight of the seeds after being dehydrated in an oven of 104°C to constant weight (O’Reilly & De Atrip 2007).…”