| Characterization of pollen grains of some wheat cultivars-Scanning
Electron Microscopy M. A. KARIM1), M. P. SINGH and S. L. MEHTA2) Indian Agricultural Research Institude New Delhi-110012 India With a view to ascertain minute structural differences of pollen grain surface , scanning through electron microscope was undertaken in four wheat cultivars (Chinese Spring, NP 880, HD 2009 and Mex. C.B. 116), which were having diverse genetic background and distinct contrasting morphological features . Mature pollen grains were collected from anthers prior to anthesis and the pollen grains were immediately boiled in a mixture of 9 parts acetic acid and one part concentrated H2SO4 for 6 minutes. The extracted pollen grains were rinsed in distilled water and subsequently fixed in the solution of 6.5% glutaraldehyde in cacodylate buffer (pH 7.2) for one hour at 8C. The pollen grains after washing were transferred to solution of cacodylate buffered 2% Osmium tetraoxide and post fixed for one hour and then passed through series of graded alcohol for dehydration at room temperature. The dried samples of pollen grains were mounted on the aluminium slubs coated with a thin layer of gold having 200Ao thickness and were examined on S4-10 Cambridge Stereoscan, Electron microscope at 10 Kv accelerating voltage. Results and Discussion Exine sculpturing of pollen grain as viewed under scanning showed two components, first indicating density process (the number of particulates /granulars/ protrusions per unit area) and the second pertains to frequency of group aggregations. The pollen grain of all the four varieties were oval in shape and their relative size was in descending order of NP 880, HD 2009, Mex. C.B. 116 and Chinese Spring. Many of the pollen grains showed single germ pore in the form of small hump on the surface and some of the germ pores had holes at the tip of the hump. The surface projections were not sharp enough to be termed as spines, hence we thought it appropriate to use inter-changeable terminology of particulates and protrusions for the granular structures. The particulates were densely packed on the pollen surface of HD 2009 and Chinese spring. The protrusions of NP 880 and Mex C.B. 116 pollen, however revealed some minor gaps in between. The particulates of NP 880 and Chinese spring pollen were alike with comparatively smooth tips. Then average diameter of these particulates was 0.07 and 0.05micro and their height was of 0.1micro and 0.07micro respectively. The particulates of HD 2009 were slightly sharper, but these were blunt tipped in Mex C.B. 116. The average diameter of particulates of HD 2009 and Mex C.B. 116 was 0.09micro and 0.12micro and their heights 0.14micro and 0.18micro respectively. The average size of the particulate at the hump of the germpore in the Chinese Spring was more distinct and prominent when compared to that of surface protrusions (Fig. 1 and 2). |
| 1) Department of Botany, Bangladesh Agricultural University, Bangladesh.
2) Division of Biochemistry, Indian Agricultural Research Institute, New Delhi. |
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