Abstract
Pinus Koraiensis seeds have physiological dormancy. Cold stratification releases seed dormancy. The changes in metabolite profiles of dormant seeds and cold stratified seeds during shorter incubation time in a favorable condition for seed germination have been studied. However, a more-long-term detection of the changes in metabolites in dormant seeds can identify the real metabolic pathways responsible for dormancy. Metabolite composition was investigated in embryo and megagametophyte of primary physiological dormant seeds (DS) of P. Koraiensis collected at 0, 1, 2, 4, and 6 weeks of incubation and of non-primary physiological dormant seeds (NDS) sampled at 0 and 1 week of incubation, seed coat rupture stage, and radicle protrusion stage. Embryos contained higher levels of most metabolites than megagametophyte. Strong accumulation of most metabolites in DS occurred at 1 and 4 weeks of incubation. A larger reduction in the relative levels of most phosphorylated sugars and amino acids in NDS was found between 1-week-incubation and seed coat rupture stage. The relative levels of metabolites involved in carbohydrate metabolism, especially the pentose phosphate pathway (PPP) and tricarboxylic acid (TCA) cycle, were higher in the embryos of 4-week-incubated DS, but the relative contents of intermediate metabolites of most amino acid metabolism were lower compared to 1-week-incubated NDS. We suggested that the disturbed carbohydrate metabolism and amino acid metabolism in the embryos of DS after 4 weeks of incubation maybe related to primary dormancy. Our study provides information for a better understanding of the mechanism of seed dormancy.
Highlights
Seed germination is a very complex physiological and biochemical process that is mainly determined by genetic factors with a substantial environmental influence (Joosen et al, 2013)
The transition from 1W to 2W was associated with smaller differences in the relative contents of metabolites in both embryos and megagametophytes
All measured metabolites were higher in the embryo than that in megagametophyte in both dormant seeds (DS) and non-primary physiological dormant seeds (NDS)
Summary
Seed germination is a very complex physiological and biochemical process that is mainly determined by genetic factors with a substantial environmental influence (Joosen et al, 2013). Due to the importance of agriculture and the availability of genome sequence data, the genomic, transcriptomic, and proteomic studies of seed germination have largely focused on model species, such as Arabidopsis thaliana (Nakabayashi et al, 2005; Holdsworth et al, 2008a,b; Narsai et al, 2017a), rice (Oryza sativa) (Narsai et al, 2017b), maize (Zea mays) (Sekhon et al, 2013), barley (Hordeum vulgare) (Lin et al, 2014), and wheat (Triticum aestivum) (Yu et al, 2014). Despite recent advances in omics studies of seed germination, few experiments focus on the mechanisms involved in seed dormancy in woody plants from a metabolomic point of view
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