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

摘要

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 1ndash;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 hypocotylndash;cotyledon was synchronized over a period of 5ndash;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 2ndash;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.