Conifer Reproductive BiologyWhen it comes to reproduction, gymnosperms are deeply weird. Cycads and co- fers have drawn out reproduction: at least 13 genera take over a year from polli- tion to fertilization. Since they don’t apparently have any selection mechanism by which to discriminate among pollen tubes prior to fertilization, it is natural to w- der why such a delay in reproduction is necessary. Claire Williams’ book celebrates such oddities of conifer reproduction. She has written a book that turns the context of many of these reproductive quirks into deeper questions concerning evolution. The origins of some of these questions can be traced back Wilhelm Hofmeister’s 1851 book, which detailed the revolutionary idea of alternation of generations. This alternation between diploid and haploid generations was eventually to become one of the key unifying ideas in plant evolution. Dr. Williams points out that alter- tion of generations in conifers shows strong divergence in the evolution of male and female gametes, as well as in the synchronicity of male and female gamete development. How are these coordinated to achieve fertilization? Books on conifer reproduction are all too rare. The only major work in the last generation was Hardev Singh’s 1978 Embryology of Gymnosperms, a book that summarized the previous century’s work. Being a book primarily about embry- ogy, it stopped short of putting conifer reproduction in a genetic or evolutionary context. |
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Common terms and phrases
Aderkas adult sporophyte alleles American Journal angiosperm Araucariaceae archegonia Canadian Journal chromosomal cone Conifer Reproductive Biology conifers corrosion cavity Cupressaceae Cupressus diploid edible pine seed egg cell embryo development embryo lethal system embryogeny evolution female gametophyte female strobili fertilization Forest fossil gametes gene genera genetic genome germination gymnosperms haploid haplotypes heterospory hybrid inbreeding depression Journal of Botany karyotypic Koski Larix LePage lethal equivalents lethal factors loblolly pine male and female male gametophyte male strobilus marker mating system megaspore meiosis meiotic Mesozoic micropylar microspore mother cell multiple archegonia nucellus nuclei organelle outcrossing ovule Owens patterns Photo Pinaceae pine Pinus pine pollen Pinus krempfii Pinus spp Pinus taeda Podocarpaceae pollen grain pollen tube pollen wall pollination drop polyembryony proembryo Pseudolarix Pseudotsuga recombination sacci seed plants self-pollination selfed embryo death Silvae Genetica simple polyembryony Singh sperm spores sporophyte stage strobilus suspensor Table taxa tetrad tissues tree viability Wollemi pine zygote