Dark-mediated dormancy release in stratified Lolium rigidum seeds is associated with higher activities of cell wall-modifying enzymes and an apparent increase in gibberellin sensitivity |
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Authors: | Danica E Goggin Stephen B PowlesPeter E Toorop Kathryn J Steadman |
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Institution: | a Australian Herbicide Resistance Initiative, School of Plant Biology (M086), University of Western Australia, 35 Stirling Highway, Crawley 6009, Australia b Royal Botanic Gardens, Kew, Seed Conservation Department, Wakehurst Place, Ardingly, Haywards Heath, West Sussex RH17 6TN, UK c School of Pharmacy and School of Biological Sciences, University of Queensland, Brisbane 4072, Australia |
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Abstract: | Dormancy release in freshly matured, imbibed annual ryegrass (Lolium rigidum) seeds is inhibited by light and involves a decrease in seed sensitivity to abscisic acid. Other processes involved in dormancy release in the dark were investigated by measuring seed storage compound mobilisation and the activity of cell wall-degrading enzymes. Activities of endo-β-mannanase and total peroxidase were higher in dark-stratified compared to light-stratified seeds, indicating that weakening of the structures constraining the embryo was accelerated in the dark. A dramatic degradation of storage proteins in light-stratified seeds, accompanied by induction of a high molecular mass protease, suggests that maintenance of storage(-like) proteins is also important in dark-mediated dormancy release. α-Amylase activity was induced in dark-stratified seeds at least 48 h prior to radicle emergence upon transfer to conditions permitting germination, or in light-stratified seeds supplied with exogenous gibberellin A4. This suggests that (a) α-amylase is involved in stimulation of germination of non-dormant L. rigidum seeds, and (b) dark-stratified seeds have an increased sensitivity to gibberellins which permits the rapid induction of α-amylase activity upon exposure to germination conditions. Overall, it appears that a number of processes, although possibly minor in themselves, occur in concert during dark-stratification to contribute to dormancy release. |
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Keywords: | DTT dithiothreitol GA gibberellin Hepes N-2-hydroxyethylpiperazine-N&prime -2-ethanesulphonic acid ICL isocitrate lyase PMSF phenylmethylsulphonyl fluoride |
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