| From the grouping pattern of particulates on the surface of pollen, it
became evident, that maximum groups occur in Chinese Spring. Frequency distribution
data compiled in Table 1 would indicate that aggregation
of 6-12 particulates were invariably present in NP 880. Maximum number of
particles were single, but fusion of two particulates was quite frequent.
Co-joining of three - six particulates was also noticed, but their frequency
of occurrence was somewhat restricted. The distribution pattern of particulates
showed mutual aggregation in all the pollen. On the basis of protrusions
length, HD 2009 and Mex. C.B. 116 formed one group, whereas NP 880 and Chinese
Spring were separately grouped. Chinese spring had small pollen grain size
with collapsed surface, indicating hollow nature. It also manifested comparatively
low seed wt. (100 grain wt. 2.2 gm.), maximum frequency of surface protrusions,
complex aggregations, and reduced protrusion height and diameter. It may
be mentioned that some of these distinct characteristics depicted at morphological
and ultra-structural levels indicated a separate position of Chinese Spring.
The sculpturing of pollen grain is generally considered a fairly constant
character and an excellent means of recognition (Faegri & Iverson 1975).
It has been suggested by Gornall, 1977 that aggregation pattern of particulates
may be linked with the breeding system and in the course of selection it
underwent rapid evolution. The adoptive significance of specific sculpturing
type as manifested on pollen grain surface is not yet clearly known, but
some ideas have been put forward on the basis of studies of pollen grain
and spore walls (Heslop Harrison 1971). There is hardly any report on scanning
studies pertaining to pollen grain. Surface in wheat crop, therefore, the
present investigation indicate the relevance of ultrastructural studies
to understand evolutionary trends and taxonomic potentials for characterization
and grouping of wheat cultivars. References FAERGI, K and J. IVERSON 1975. Textbook of pollen analysis. Blackwell Scientific Publications, Oxford London, 205 pp. GORNALL, R. J. 1977. Notes on the size and excise ornamentation of Avena pollen grains. Canad. J. Bot. 55, 2622-2629. HESLOP-HORRISON, J. 1971. Sporopollenin in the biological context. In sporopollenin, ed. J. B. Brooks: P. R. Grant; M. Muir; P. Van Gizzel and G. Shano. Academic Press, London and New York, pp-1-30. |
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