Jeffrey Carmichael

Associate Professor
B.S., 1990, Slippery Rock University
Ph.D., 1995, University of Georgia

Plant Anatomy, Reproductive Biology, and Cell Biology.

Tel. (701) 777-4666 or 777-2621
e-mail: jeffrey_carmichael@und.nodak.edu

Other Web Pages by Jeff Carmichael

I am interested in all aspects of plant biology that emphasize plant structure and function.   Most recently, I have been studying the development of gametes in plants that appear to form embryos asexually.  Sperm and eggs are formed, but they don't seem to fuse during the fertilization process.  Instead, unfertilized egg cells develop into embryos after pollination takes place.  These types of studies are aimed at increasing our understanding of the development and role of gametes during the reproductive process in higher plants.

My previous work has focused on the reproductive biology of the Gnetales (Ephedra, Gnetum, and Welwitschia), an intriguing group of gymnosperms that are closely related to flowering plants.  As part of this work, I documented the fertilization process in Gnetum gnemon in order to further our understanding of the evolution of sexual reproduction within the Gnetales, and more broadly, among seed plants. When viewed within a phylogenetic context, sexual reproduction in Gnetum has implications in three general areas.
1. Origin and Evolution of Double Fertilization . Sexual reproduction in flowering plants occurs by a process of double fertilization in which one fertilization event forms an embryo and a second fertilization event produces endosperm, a polyploid embryo-nourishing tissue found only in angiosperms. Recently, a rudimentary form of double fertilization has been documented within the Gnetales in the genus Ephedra . I have found that a process of double fertilization also occurs in Gnetum gnemon which results in the production of two embryo products, endosperm is not formed. The documentation of double fertilization in Ephedra and Gnetum is congruent with the hypothesis that this process evolved prior to the origin of flowering plants.
2. Relationship Between the Cell Cycle and Fertilization Events . With the advent of in vitro fertilization techniques and regeneration of genetically engineered zygotes, there is heightened interest in the relationship between the cell cycle and sexual reproduction in higher plants. By quantifying DNA in male and female gametophyte nuclei in Gnetum gnemon , it was found that gamete nuclei pass through the synthesis phase of the cell cycle prior to fusion. This reproductive cell cycle pattern was defined as "G2 Karyogamy" and is one of three patterns found among seed plants. Future cell cycle studies will likely serve to increase our understanding of the unique process of gamete fusion in higher plants.
3. Evolution of the Seed Plant Female Gametophyte . In primitive seed plants (cycads, conifers, and Ginkgo ) the female gametophyte undergoes complete development prior to fertilization and serves to nourish developing embryos. In Gnetum gnemon , the female gametophyte is highly reduced at the time of fertilization and develops into an embryo-nourishing tissue only after fertilization occurs. Postfertilization embryo-provisioning in Gnetum is analogous to endosperm formation in flowering plants. Consequently, this energy-efficient strategy has evolved separately in flowering plants and Gnetales. In addition, the reduced nature of the sexually mature female gametophyte in Gnetum is a result of heterochrony and represents a paedomorphic effect.

Carmichael, J.S.  2003.  Plant growth and development: fertilisation.  Encyclopedia of Applied Plant Sciences.  Academic Press, Ltd. 

Carmichael, J.S.  2001.  Gnetales.  Encyclopedia of Life Sciences.  Nature Publishing Group, Macmillan Publishers Ltd.

Haycraft, C.J. and J.S. Carmichael.  2001.  Development of sterile ovules on bisexual strobili of Gnetum gnemon.  American Journal of Botany 88: 1326-1330.

Carmichael, J.S. and S.M. Selbo.  1999.  Ovule, embryo sac, embryo, and endosperm development in leafy spurge (Euphorbia esula L.).  Canadian Journal of Botany 77:599-610.

Selbo, S.M. and J.S. Carmichael.  1999.  Reproductive biology of leafy spurge (Euphorbia esula L.): breeding system analysis. Canadian Journal of Botany 77: 1-5.

Friedman, W.E., and J.S. Carmichael. 1998. Heterochrony and developmental innovation: evolution of female gametophyte ontogeny in Gnetum, a highly apomorphic seed plant. Evolution 52: 1016-1030.

Carmichael, J.S. and W.E. Friedman. 1995. Double Fertilization in Gnetum gnemon: The Relationship between the Cell Cycle and Sexual Reproduction. The Plant Cell. 7: 7: 1975-1988.

Friedman, W.E., and J.S. Carmichael. 1996. Double fertilization in Gnetales: implications for understanding reproductive diversification among seed plants. International Journal of Plant Sciences 157: S77-S94.

Carmichael, J.S. and W.E. Friedman. 1996. Double fertilization in Gnetum gnemon (Gnetaceae): Its bearing on the evolution of sexual reproduction within the Gnetales and the Anthophyte clade. American Journal of Botany 83: 767-780.