Biochemical events during germination and early growth of somatic embryos and seed of interior spruce (Picea glauca engelmannicomplex)

Abstract

Utilization of lipid and protein storage reserves was examined during germination and early growth of somatic and excised seed embryos in vitro, and seed of interior spruce. High germination frequencies were recorded for somatic and excised seed embryos, and elongation of radicles and hypocotyls observed for both embryo types. Although elongation of the embryo types differed (i.e. somatic ≤ excised seed < seed), fresh weight gain was similar. Utilization of triglycerides in somatic embryos was more rapid than in excised seed and seed embryos, thus it appeared to be under embryo infuence. By contrast, depletion of storage proteins appeared to be influenced by the megagametophyte, with hydrolysis in somatic and excised seed embryos preceding that of the seed embryo by 2 days. Differential utilization of the storage reserves was temporally associated with differences in growth patterns of somatic and seed embryos. The evidence presented indicates that the in vitro germination medium does not entirely supplant the role of the megagametophyte during germination and early growth. The relevance of these results to artificial seed technology is discussed.

Morphogenic Aspects of Somatic Embryogenesis

“…In support of this, the application of ABA to microspore-derived rapeseed embryos stimulated storage protein transcript accumulation [208] and promoted the correct developmental induction of storage protein transcripts to levels comparable to equivalent stage zygotic embryos [211]. Developing Norway and interior spruce somatic embryos matured on ABA displayed storage protein levels similar to those of zygotic embryos [202,215,216], with similar developmental patterns of storage protein transcript appearance [217] and protein accumulation [202,217], as developing zygotic embryos. Furthermore, reduced levels of ABA resulted in lower levels of storage protein accumulation [166].…”

“…Rapeseed microspore embryos contained triglyceride levels that were similar to those of the dry seed, based on dry weight [208] and percentage of total lipid [220]. Interior spruce somatic embryos contained similar triglyceride levels to zygotic embryos on a per embryo basis, but genotype differences were noted between the somatic embryos [215]. White spruce embryos contained five times the triglyceride levels on a per embryo basis as compared to zygotic embryos [227].…”

“…Storage protein and lipid degradation occurred in dried spruce somatic embryos following imbibition [206,215,223]. Protein and lipid reserves declined substantially within one day following imbibition, well before radicle elongation [215]. This was more rapid than in seed embryos, and suggested that the kinetics of reserve degradation differed between zygotic and somatic embryos, probably as a result of the lack of surrounding nutritive seed tissues in the somatic embryo.…”

“…Storage protein and lipid degradation occurred in dried spruce somatic embryos following imbibition [206,215,223]. Protein and lipid reserves declined substantially within one day following imbibition, well before radicle elongation [215].…”

Screening RAPD primers to assess clonal fidelity in somatic embryos of Sawara cypress (<i>Chamaecyparis pisifera</i> Sieb. et Zucc.) and field performance of somatic embryo-derived trees

“…Similarly, Bozhkov and von Arnold (1998) and Högberg et al (2001) reported inferior growth increment in somatic plants versus that in seedlings of Picea abies. For the same species, Cyr et al (1991) reported that the differences between somatic plants and seedlings occurred early during plant development. Although somatic plants were consistently shorter than seedlings after the first growth period, the differences in height decreased by the end of the second growth period (Högberg et al 2003).…”