Synchronous and high frequency germination of interior spruce somatic embryos following partial drying at high relative humidity

Abstract

The germination of mature somatic embryos of interior spruce was limited by the low frequency of root emergence. In addition, development was abnormal, since elongation and greening of the hypocotyl and cotyledons preceded root emergence by 1–2 weeks. Pretreatment of the embryos on water-saturated Kim-paks increased the frequency of root emergence but did not alter the abnormal pattern of germination. Somatic embryos do not survive desiccation at room humidity, but partial drying at high humidity promoted germination up to 90%. Furthermore, this treatment decreased the time required for root emergence such that elongation of the root and hypocotyl–cotyledon was synchronized over a period of 5–6 days. This germination closely resembled that of excised zygotic embryos. Drying over a range of humidities indicated that humidities of 81% and lower were lethal to the embryos, whereas germination was enhanced following treatment at humidities greater than 95% relative to untreated controls. The best germination and root elongation occurred on one-half strength basal media containing 2–3.4% sucrose. Of the plantlets derived from treated embryos, 50% survived transfer to soil compared with only 5% of the untreated controls. Key words: conifers, desiccation, germination, high relative humidity, partial drying, somatic embryogenesis, spruce.

Somatic Embryogenesis and Efficient Plant Regeneration in Japanese Cypresses

“…The maturation frequency and the quality of embryo produced are the key criteria for the optimization of an efficient plant regeneration system via somatic embryogenesis. The cotyledonary somatic embryos of the Hinoki and Sawara cypress readily germinated after transfer to a PGR-free medium without any kind of post-maturation treatment, as was previously reported as necessary to promote the germination of somatic embryos of some other species (Roberts et al, 1990b;Roberts et al, 1991;Kong and Yeung, 1992;Kong and Yeung, 1995;Jones and van Staden, 2001). Thus, most of the germinants developed epycotyl and grew into normal plants.…”

Somatic embryogenesis of selected spruce species (Picea abies, P. omorika, P. pungens 'Glauca' and P. breweriana)

“…The highest germination rate (35%) was recorded by von Arnold and Hakman (1988) for somatic embryos of P. abies. Good results of germination were also achieved by means of partial drying of cotyledonary embryos at a relatively high humidity (Roberts et al 1990). …”

Stimulation of somatic embryo growth and development in Picea spp. by polyethylene glycol

“…As a result, the overall benefit of exposing embryogenic lines to various concentrations of PEG in the maturation medium remains controversial (Hudec et al, 2016). Somatic embryos in many conifer species are partially dried at high relative humidity or desiccated in the presence of supersaturated solutions of salt in order to improve germination and conversion rates (Roberts et al, 1990;Jones & van Staden, 2001;Dronne et al, 1997). This approach has also been used in our recent studies (Hazubska-Przybył et al, 2015) and resulted in an improvement in radicle growth in both P. abies and P. omorika embryos when they were exposed to partial drying at 97% relative humidity for 2 weeks.…”