Pollen Development

The mature male gametophyte is a tricellular pollen grain, consisting of two small sperm cells enclosed within a larger vegetative cell which will grow the pollen tube

Pollen development begins with meiosis, which creates four grains enclosed in a callose wall: the tetrad. Breakdown of the callose releases the microspores. These polarize, with a large vacuole (gray) at one end and a nucleus (black) at the other, preparing the grain for an asymmetric cell division. The cell plate formed during pollen mitosis I has a distinctive hemisperical shape, and after division is completed the smaller generative cell detaches from the cell wall and in enveloped within the vegetative cell. The generative cell undergoes another round of cell division to form the two sperm cells of the mature pollen grain.

Click on the links at the top of the page to see images of wild type pollen development using three different microscopy methods. I took these images while a graduate student in the lab of Sebastian Bednarek in the Department of Biochemistry at the University of Wisconsin, Madison, while studying a mutant (dynamin related protein 2) with defective pollen development (Backues et al. (2010) Plant Cell 22:3218-3231).

Reviews of pollen development:

Gómez J.F., Talle B. and Wilson, Z.A. (2015) Anther and pollen development: A conserved developmental pathway J Integr Plant Biol. 57:876-891 DOI: 10.1111/jipb.12425

Borg, M, Brownfiled, L. and Twell, D. (2009) Male gametophyte development: a molecular perspective. J. Exp. Botany 60:1465-1478 DOI: 10.1093/jxb/ern355

Original papers with pictures and descriptions of pollen morphology during development:

Owen, H.A., and Makaroff, C. (1995). Ultrastructure of microsporogenesis and microgametogenesis in Arabidopsis thaliana (L.) Heynh. ecotype Wassilewskija (Brassicaceae). Protoplasma 185: 7–21.

Brown, R., and Lemmon, B. (1991). Pollen development in orchids. 5. A generative cell domain involved in spatial control of the hemispherical cell plate. J. Cell Sci. 100: 559–565.

Regan, S., and Moffatt, B. (1990). Cytochemical Analysis of Pollen Development in Wild-Type Arabidopsis and a Male-Sterile Mutant. Plant Cell 2: 877-889