Traditional methods of preparation of botanical specimens for scanning electron microscopy (SEM) have proven to induce artifacts in some specimens which often reduce quality of resulting images, and are highly misleading for taxonomic purposes. The advantages of low temperature SEM are illustrated by an investigation of freshly collected flowers, using a cryo-system interfaced to an SEM. This method overcame the deficiencies of traditional procedures to produce exceptional images of floral surfaces in their natural state. Depending on the nature of the material under investigation, the method my be indispensable (e.g., for accurate details of petal surfaces), preferable (e.g., glandular hairs are better shown than by critical point drying), inefficient (e.g., images of stigmas of equivalent clarity are obtainable by direct examination of unfixed uncoated material), or unrewarding (e.g., examination of dry herbarium specimens). This paper stresses previously unappreciated adaptive and taxonomic importance of microtopography of floral surfaces of several genera important as agricultural forage crops. Certain species have evolved adaptive petal surface microsculpturing that facilitates cross-pollination by their insect associates. In the cross-pollinating species examined, different petal areas appear to be specialized for the landing of pollinating insects, and perhaps also as tactile (braille-like) orientation guides to the hidden nectaries. By contrast, in related self-pollinating species and cultivars, and when flowers are clustered in a head that provides a landing platform for pollinators, these adaptations are reduced or absent.
Brookes, Brenda and Small, Ernest
"Enhanced Floral Analysis by Low Temperature Scanning Electron Microscopy,"
Scanning Microscopy: Vol. 2
, Article 22.
Available at: https://digitalcommons.usu.edu/microscopy/vol2/iss1/22