Summary
Brassica napus pollen development during the formation of the generative cell and sperm cells is analysed with light and electron microscopy. The generative cell is formed as a small lenticular cell attached to the intine, as a result of the unequal first mitosis. After detaching itself from the intine, the generative cell becomes spherical, and its wall morphology changes. Simultaneously, the vegetative nucleus enlarges, becomes euchromatic and forms a large nucleolus. In addition, the cytoplasm of the vegetative cell develops a complex ultrastructure that is characterized by an extensive RER organized in stacks, numerous dictyosomes and Golgi vesicles and a large quantity of lipid bodies. Microbodies, which are present at the mature stage, are not yet formed. The generative cell undergoes an equal division which results in two spindle-shaped sperm cells. This cell division occurs through the concerted action of cell constriction and cell plate formation. The two sperm cells remain enveloped within one continuous vegetative plasma membrane. One sperm cell becomes anchored onto the vegetative nucleus by a long extension enclosed within a deep invagination of the vegetative nucleus. Plastid inheritance appears to be strictly maternal since the sperm cells do not contain plastids; plastids are excluded from the generative cell even in the first mitosis.
Similar content being viewed by others
References
Brighina L, Cecchi Fiordi A, Palandri MR (1981) Ultrastructural investigations on the two-nucleate pollen grain of Tillandsia caput-medusae Morr (Bromeliaceae). Am J Bot 68:1033–1041
Charzynska M, Murgia M, Milanesi C, Cresti M (1989a) Origin of sperm cell association in the “male germ unit” of Brassica pollen. Protoplasma 149:1–4
Charzynska M, Murgia M, Cresti M (1989b) Ultrastructure of the vegetative cell of Brassica napus pollen with particular reference to microbodies. Protoplasma 152:22–28
Dumas C, Knox RB, Gaude T (1985) The spatial association of the sperm cells and vegetative nucleus in the pollen grain of Brassica. Protoplasma 124:168–174
Grant I, Beversdorf WD, Peterson RL (1986) A comparative light and electron microscopic study of microspore and tapetal development in male fertile and cytoplasmic male sterile oilseed rape (Brassica napus). Can J Bot 64:1055–1068
Hagemann R (1983) The formation of generative and sperm cells without plastids in angiosperms and the underlying mechanisms. In: Erdelska O (ed) Fertilization and embryogenesis in ovulated plants. VEDA, Bratislava, pp 97–99
McConchie CA, Jobson S, Knox RB (1985) Computer-assisted reconstruction of the male germ unit in pollen of Brassica campestris. Protoplasma 127:57–63
McConchie CA, Russell SD, Dumas C, Tuohy M, Knox RB (1987) Quantitative cytology of the sperm cells of Brassica campestris and Brassica oleracea. Planta 170:446–452
Murgia M, Wilms HJ, Cresti M, Cesca G (1986) Ultrastructure of pollen development in Euphorbia dulcis L. 1. Diploid plants. Acta Bot Neerl 35:405–424
Schröder MB (1984) Ultrastructural studies on plastids of generative and vegetative cells in the family Liliaceae. Biol Zentralbl 103:547–555
Sears BB (1980) Elimination of plastids during spermatogenesis and fertilization in the plant Kingdom. Plasmid 4:233–255
Spurr AR (1969) A low-viscosity resin embedding medium for electron microscopy. J Ultrastr Res 44:31–43
Tuohy M, McConchie C, Knox RB, Szarski L, Arkin A (1987) Computer-assisted three-dimensional reconstruction technology in plant cell image analysis: applications of interactive computer graphics. J Microsc 147:83–88
Vergne P, Delvalle I, Dumas C (1987) Rapid assessment of microspore and pollen development stage in wheat and maize using DAPI and membrane permeabilization. Stain Technol 62:299–304
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Murgia, M., Detchepare, S., Van Went, J.L. et al. Brassica napus pollen development during generative cell and sperm cell formation. Sexual Plant Reprod 4, 176–181 (1991). https://doi.org/10.1007/BF00190001
Issue Date:
DOI: https://doi.org/10.1007/BF00190001