Abstract
THE chief purpose of Mepham and Lane in their recent article1 seems to be to establish that the exine of the pollen grain is formed by secretion from within the microspore and owes little or nothing to the activity of the disorganizing tapetum. Their interesting new observations and their substantial claims to reinterpretation of the ontogeny of the pollen grain suffer from over-condensation, and it is a pity that they had no space to consider other recent electron microscope studies, at close time intervals, of pollen grain development from the pollen-mother cell stage to pollen maturity2–6. They claim that in Tradescantia bracteata “the bulk of the exine is produced at an early stage”. Heslop-Harrison's pioneer study of Silene pendula2, however, made it clear that, although the pattern of the exine is clearly determined while the microspores are within their own callose envelopes and the common callose envelopes of the pollen mother cell, the most important part of exine development occurs after dissolution of the callose walls and exposure of the exine to the fluid of the anther loculus. A similar conclusion has emerged from studies of Helleborus foetidus and Endymion non-scriptus made in the Botany School, Cambridge3–6.
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References
Mepham, R. H., and Lane, G. R., Nature, 219, 961 (1968).
Heslop-Harrison, J., Grana Palynol., 4, 7 (1963).
Echlin, P., Chapman, B., Godwin, H., and Angold, R., Proc. Sixth Intern. Cong. Electron Microsc., Kyoto, Electron Microsc., 2, 315 (1966).
Echlin, P., and Godwin, H., J. Cell Sci., 3, 161 (1968).
Echlin, P., and Godwin, H., J. Cell Sci., 3, 175 (1968).
Angold, R. E., Rev. Palaeobot. Palynol., 3, 205 (1968).
Godwin, H., Echlin, P., and Chapman, B., Rev. Palaeobot. Palynol., 3, 181 (1967).
Chambers, T. C., and Godwin, H., New Phytol., 60, 393 (1961).
Dunbar, A., Grana Palynol., 7, 10 (1967).
Goodwin, II., New Phytol., 67, 667 (1968).
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GODWIN, H. Pollen Exine Formation. Nature 220, 389 (1968). https://doi.org/10.1038/220389a0
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DOI: https://doi.org/10.1038/220389a0
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