Seed plants have a diplohaplontic life cycle which has two phases. The first is a dominant, concurrent sporophyte phase and the second is a brief gameto-phyte phase; both phases are multicellular so somatic growth follows meiosis and somatic growth follows the union of gametes or syngamy. But even so, there are variants within this basic plan. Some angiosperm species, like bamboo, flower only once at the end of life. Conifers, by contrast, are long-lived iteroparous species which can produce male and female gametophytes annually for hundreds or even thousands of years. Each year, the adult sporophyte gives rise to a new set of indeterminate meristems at the telescoping ends of the latest branch tips and some of these branch tips develop either male or female reproductive initials. Conifers thus have meristems which produce both vegetative and reproductive growth as opposed to the predetermined germline typical of the diplontic life cycle of vertebrates. This “moving interface” between vegetative and reproductive cell lineages has not been well-studied in conifers and it constitutes a fertile area for exploring adaptive response, mutational accumulation, DNA repair systems and regulatory cues.
KeywordsHydrate Recombination Germinate Gibberellin Century Botanist
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- Burris, L., C. Williams, et al. 1992. Scion age and its effect on flowering and early selection age. Knoxville, TN, Southern Forest Tree Conference.Google Scholar
- Dorman, K. 1976. The Genetics and Breeding of Southern Pines. Washington, DC, US Department of Agriculture, Forest Service U.S. Government Printing Office.Google Scholar
- Ferguson, M. 1904. Contributions to the life history of Pinus with special reference to sporo-genesis, the development of gametophytes and fertilization. Proceedings of the Washington Academy of Science 6: 1–202.Google Scholar
- Hofmeister, W. 1851. Vergleichende Untersuchungen der Keimung, Entfaltung und Fruchbiung hoherer Kryptogamen (Moose, Farrn, Equisetceen. Rhizocarpeen und Lycopodiaceen) und der Samenbildung der Coniferen. Leipzig.Google Scholar
- Klekowski, E. 1988. Genetic load and its causes in long-lived plants. Trees 55: 195–203.Google Scholar
- Korol, A., I. Preygel, et al. 1994. Recombination Variability and Evolution. Chapman & Hall, London.Google Scholar
- Kozlowski, T. 1971. Growth and development of trees. Vol. 1. Seed Germination, Ontogeny and Shoot Growth. Academic, New York.Google Scholar
- Matziris, D. 2002. Short note: Hemaphroditism in black pine. Silvae Genetica 51: 130–131.Google Scholar
- Richards, A. 1997. Plant Breeding Systems. Chapman & Hall, London.Google Scholar
- Singh, H. 1978. Embryology of Gymnosperms. Gebruder Borntraeger, Berlin.Google Scholar
- Skinner, D. 1992. Ovule and embryo development, seed production and germination in orchard grown control pollinated loblolly pine (Pinus taeda L.) from coastal South Carolina. Master's thesis, Department of Biology, University of Victoria, Victoria, BC, 88 pp.Google Scholar
- Strasburger, E. 1894. The periodic reduction of the number of chromosomes in the life history of living organisms. Annals of Botany 8: 281–316.Google Scholar