Journal of Plant Research

, Volume 117, Issue 4, pp 265–276

Correlation between pollen morphology and pollination mechanisms in the Hydrocharitaceae

Original Article

DOI: 10.1007/s10265-004-0155-5

Cite this article as:
Tanaka, N., Uehara, K. & Murata, J. J Plant Res (2004) 117: 265. doi:10.1007/s10265-004-0155-5

Abstract

The pollen morphology of 11 genera and 11 species of the Hydrocharitaceae and one species of the Najadaceae was studied using scanning and transmission electron microscopies, and the exine structures and sculptures are discussed in relation to pollination mechanisms and the molecular phylogeny. The pollen grains of the Hydrocharitaceae are spherical, inaperturate, and form monads or tetrads, while those of the Najadaceae are elliptical, inaperturate, and form monads. The entomophilous genera Egeria, Blyxa, Ottelia, Stratiotes, and Hydrocharis share pollen grains that have projections like spines or bacula. The anemophilous genus Limnobium has reticulate pollen grains. The hypohydrophilous genera Thalassia and Najas are characterized by pollen grains with reduced exine structures. The pollen-epihydrophilous genera Elodea and Hydrilla have tightly arranged small spinous pollen grains, and the male flower-epihydrophilous genera Enhalus and Vallisneria have reduced reticulate or gemmate exines. Character state reconstruction of the exine structures and sculptures using a molecular phylogenetic tree suggests that variation in the exine is generally correlated with the pollination mechanism; the selective pressures acting on the pollination mechanisms have reduced the exine structure in hypohydrophilous plants and resulted in various exine sculptures that are adapted to the different pollination mechanisms in entomophilous, anemophilous, and pollen-epihydrophilous plants.

Keywords

Exine Hydrocharitaceae Hydrophily Phylogeny Pollen Pollination 

Copyright information

© The Botanical Society of Japan and Springer-Verlag  2004

Authors and Affiliations

  1. 1.Tsukuba Botanical GardenNational Science MuseumTsukuba 305-0005Japan
  2. 2.Laboratory of Plant Morphology, Faculty of HorticultureChiba UniversityChibaJapan
  3. 3.Botanical Gardens, Graduate School of ScienceUniversity of TokyoTokyoJapan

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