Pollen Evolution

Research on the morphology and development of pollen and tapetum has contributed to understanding the evolution of these characters and elucidating phylogenetic relationships among seed plants.

Scanning electron micrograph of pollen of Meliosma pinnata ssp. macrophylla (Sabiaceae). Polar view showing three colporate apertures. Scale bar = 5 µm.

Considerable depth of expertise in comparative pollen morphology at Kew includes Carol Furness (Acanthaceae, monocots, eudicots, Ericaceae, Malpighiales, general and developmental), Hannah Banks (Fabales, Nelumbonaceae), Paula Rudall (monocots and general), and Madeline Harley (Arecaceae, Burseraceae, Lamiaceae, Liliacae, Iridaceae and general), plus numerous research visitors.

This expertise, in parallel with improved hypotheses of angiosperm relationships based on molecular sequence data, permit the re-assessment of key pollen and anther characters in angiosperms. Work on this began with the monocots (see Monocot pollen evolution) and has been expanded since 2000 to include basal angiosperms and eudicots. This long-term project is based in the Jodrell Laboratory and involves collaborations with colleagues from Kew and other institutions. The aims are (1) to review pollen and anther characters of systematic significance throughout the angiosperms and their seed plant outgroups (e.g. tapetum type, microsporogenesis, pollen apertures, microgametophyte) and (2) to target specific groups for more detailed study, particularly Fabales (legumes and relatives) and Malpighiales. Research techniques include light microscopy and both scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

Since 2006 the distributions of plasmodial tapeta, inaperturate pollen and successive microsporogenesis have been reviewed in eudicots. An ongoing collaboration with colleagues in France is investigating the roles of selection pressure and developmental constraints in determining pollen aperture patterns. In Ericaceae, a new hypothesis for the evolution of selective microspore abortion leading to the development of pollen shed as pseudomonads in epacrids (Styphelioideae) has been presented. The evolutionary significance of the proximal-distal microspore polarity transition, a key innovation in seed plants, has been examined and found to have important downstream effects, not only on aperture location and site of germination but also on microgametophyte polarity, and, perhaps, indirectly on sperm motility.

There is a long history of research on monocot and legume (Fabaceae) pollen at RBG Kew, while work on Malpighiales pollen was begun recently. Other ongoing collaborative research focuses on pollen of Aquifoliales and Merremieae (Convolvulaceae).

Key publications 2006-2011

• Rudall, P. J. & Bateman R. M. (2007). Developmental bases for key innovations in the seed-plant microgametophyte. Trends in Plant Science 12: 317-326.
• Furness, C. A. (2009). Pollen evolution and development in Ericaceae, with particular reference to pseudomonads and variable pollen sterility in Styphelioideae. International Journal of Plant Sciences 170: 476-495.
• Furness, C. A. (2008). A review of the distribution of plasmodial and invasive tapeta in eudicots. International Journal of Plant Sciences 169: 207-223.
• Furness, C. A. (2007). Why does some pollen lack apertures? A review of inaperturate pollen in eudicots. Botanical Journal of the Linnean Society 155: 29-48.
• Furness, C. A. (2008). Successive microsporogenesis in eudicots, with particular reference to Berberidaceae (Ranunculales). Plant Systematics and Evolution 273: 211-223.