Form and Function in Angiosperm Pollen

Abstract

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Chromosomal and morphological studies of diploid and polyploid cytotypes of Stevia rebaudiana (Bertoni) Bertoni (Eupatorieae, Asteraceae)

“…Although a higher ploidy number has been associated with larger pollen (Muller, 1979), this correlation is only consistent for autopolyploids (Stebbins, 1971). In some coffee (Boaventura et al, 1981) and cassava (Carvalho et al, 1999) plants with different chromosome numbers, there is a tendency for stomata cell size to increase with the level of ploidy.…”

Pollen morphological studies in the Malvaceae

“…Earlier investigations: Lang (1937), Erdtman (1952), Datta (1958), Saad (1960), Nair (1961), Prasad (1961), Nair (1962), Prasad (1962), Chaudhuri (1965), Martin & Drew (1969), Barth (1975), Coetzee & van der Schijff (1979), Muller (1979), and Radulescu & Tamavschi (1979). n= 14, 18, 20, 28, c. 33, 40, 46, 48, 59, 60, 66 Lagunaria (l/1).-Pollen grains 58x56 11m, spheroidal, 6--9-colporate, spiral pattern distinct.…”

“…Two choose between these two alternative explanations would require a more thorough investigation of, and insight into, the functional aspects of exine morphology. Such an investigation should include the protective function, the harmomegathic function, the reservoir function and the lumping effect (Woodhouse 1935, Heslop-Harrison 1979, Muller 1979.…”

Pollen morphology in tribe Dicomeae Panero and Funk (Asteraceae)

“…The existence in its exine of a tensile system of both outer and supporting columellae constitutes good protection against compressive forces (Bolick 1978(Bolick , 1991. It must be pointed out that the thin supporting columellae of some Dicomeae (Pleiotaxinae, mainly Erythrocephalum) certainly enhance the efficiency of the harmomegathic mechanisms by increasing the flexibility of the exine (Muller 1979). Also, the presence of a multi-stratified (fragmented) internal tecta and the absence of internal foramina are effective defences against the loss of water by the male gametophyte, a clear ecological advantage in the xeric habitats where most of the species of Dicomeae live.…”