Marioara Urda _Grebenisan_ rezumat_teza_engleza - USAMV Cluj ...

Marioara GREBENIŞAN Summary of the PhD thesis
Research on the structure of di- and tetraploid red clover seed plants and the influence of meiotic
anomalies on the fertility of autotetraploid forms
The abiotic factors, which also include the weather conditions, can have a
direct or indirect influence on red clover pollination, by consistently affecting both
the flowering dynamics and the flight of the pollinators.
The comparative data collected in Cluj-Napoca show the fact that the
morphological modifications determined by the increase of the ploidy level affect
the pollination and seed formation processes, in favour of the diploid red clover
genotypes, which explains, to a certain extent, the difference in productivity
potential between the seed plants belonging to different ploidy groups (table 4.9).
There has been noticed an influence, either positive or negative, of the
weather factors upon the interrelationships red clover-pollinators. The good
understanding of the correlations between these two factors can allow for the
determination of the most favourable exploitation period for red clover seed plants.
By studying the evolution of embryogenesis it was possible to highlight the
action of multiple factors that contribute to the diminishing of the red clover
fertility.
The phases that the pollen grain goes through as part of the pollination and
fertilization process must give an answer to the question if its participation in this
process can produce any beneficial effects upon the seed yield in the case of red
clover.
The tests regarding germination, elongation, pollen viability indicators, as
well as the growth of pollen tubes in compatible and non-compatible pistils have
pointed out major differentiations between red clover genotypes with different
ploidy level.
The ploidy level correlates with pollen viability; as the percentage of
abnormal and unviable pollen is higher in tetraploids, the fertility of these genotypes
is lower (table 5.1).
The in vitro germination of pollen takes place in the first two hours after the
pollination, and the elongation of the pollen tubes is faster in the first 12 hours,
whereas in the next 12 hours the growth rate is very low.
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