Intraspecific variation in the petal epidermal cell morphology of Vicia faba L. (Fabaceae)

Emily J Bailes,Beverley J Glover

doi:10.1016/j.flora.2018.06.005

Abstract

At a microscopic scale, the shape and fine cell relief of the petal epidermal cells of a flower play a key role in its interaction with pollinators. In particular, conical shaped petal epidermal cells have been shown to have an important function in providing grip on the surface of bee-pollinated flowers and can influence bee visitation rates. Previous studies have explored interspecific variation in this trait within genera and families, but naturally-occurring intraspecific variation has not yet been comprehensively studied. Here, we investigate petal epidermal cell morphology in 32 genotypes of the crop Vicia faba, which has a yield highly dependent on pollinators. We hypothesise that conical cells may have been lost in some genotypes as a consequence of selective sweeps or genetic drift during breeding programmes. We find that 13% of our lines have a distribution of conical petal epidermal cells that deviates from that normally seen in V. faba flowers. These abnormal phenotypes were specific to the ad/abaxial side of petals, suggesting that these changes are the result of altered gene expression patterns rather than loss of gene function.

Highlights

The majority of flowers rely on animals, insects, for their pollination
The three different petal morphologies produced by V. faba – standard, wing and keel petals – had specific categories of cell types associated with them so that they could be discriminated on the basis of their epidermal cell morphology (Table 1; Figure 2; see methods for descriptions of terminology)
The results of this study represent the first comprehensive assessment of the level of variation in petal epidermal morphology within a species. It suggests that for the large part the flowers of the field bean are optimized for pollination by bees; conical cells are present on the abaxial surface of the wing petal, the most important petal surface for a bee manipulating a flower, providing grip in all of the genotypes that we analysed

Summary

Introduction

The majority of flowers rely on animals, insects, for their pollination. The epidermis of plants is highly variable in morphology, with different cell shape and cell surface textures resulting from cuticle folding and ornamentation with other compounds such as epicuticular waxes (Koch et al, 2008) These different cell structures influence the interaction of plants with pathogens, pests and mutualists by altering the grip and accessibility of the surface, as well as its optical properties (Gorton and Vogelmann, 1996; Comba et al, 2000; Whitney et al, 2009; Alcorn et al, 2012). It has been suggested that conical cells, which reduce the wettability of the flower surface, act as a self-cleaning mechanism to keep flowers free of dust and other particles which may make their surface less attractive to pollinators (Whitney et al, 2011b)

Objectives

Methods

Results

Discussion

Conclusion