Comparison of the Micromorphology and Ultrastructure of Pollen Grains of Selected Rubus idaeus L. Cultivars Grown in Commercial Plantation

The genus Rubus is one of the largest taxonomically diverse and complex genera in the family Rosaceae. Morphology of pollen grains (equatorial and polar axes length, shape and size, aperture position, exine sculpture, perforations) is regarded as one of its main diagnostic features for identification of species and varieties. An attempt was made to fill the gap concerning the pollen micromorphology and ultrastructure of R. idaeus L. using light, scanning, and electron transmission microscopy. This study is a comparative analysis of micromorphological and ultrastructural traits of pollen from six raspberry cultivars. The pollen grains were classified as small or medium of shape prolato-spheroids. The parallel striae in the equatorial view in the exine sculpture were sometimes branched dichotomously in ‘Glen Ample’, ‘Polka’, and ‘Polana’, arcuate in ‘Laszka’ and ‘Pokusa’, or irregularly overlapping in ‘Radziejowa’. The width of exine striae of biennial fruiting cultivars was much larger than in repeated fruiting cultivars. In terms of the increasing number of perforations per unit area of the exine surface, the cultivars were ranked as follows: ‘Pokusa’ < ‘Glen Ample’ < ‘Laszka’ < ‘Polka’ < ‘Polana’ < ‘Radziejowa’. The thickest tectum, the highest and thickest columellae with the largest distances between them, and the thicker foot layer were demonstrated in ‘Glen Ample’. The ectoexine constituted on average ca. 78–90% of the exine thickness. The findings may constitute auxiliary traits i.a. for identification of related taxa, interpretation of phylogenetic relationships, and pollination biology.

Convergent beam electron diffraction interferometry using an electron biprism (CBED+EBI)

Recently, a new method of interferometry has been realized which is capable of providing important information of crystals, crystal defects and electron-optical information of the microscope such as its spherical aberration surface. The method produces interferograms by using an electron biprism to interfere diffracted beams produced from a small convergent beam probe of ∼10 nm. The electron biprism uses an applied voltage of ∼15 to 100 V to deflect and compensate for the diffracted beam(s) of 2θB (typically ∼5 mrad) (Fig. 1). The biprism ∼0.3 μm dia) is inserted in between and perpendicular to the diffracted beam(s). Two biprism positions were successfully used. An “upper” biprism is placed in the selected area aperture position which is between the objective lens and 1st intermediate lens. A “lower” biprism is further down the optic axis and is placed between the 1st and 2nd intermediate lenses. In Fig. 1, the virtual image of a biprism is shown with respect to the specimen plane.