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Most of the anthers were found dorsally attached to the
mature grains in cultivars DWL 5023, WL 1562, WL 711, WG 377
and TL 419 (Fig. 1). Most likely,
these anthers were not fully mature to attain normal
versatile attachment. These did not dehisce probably due to
incomplete maturation or water imbalance in the
anther/anther walls, thus affecting pollination and
fertilization in these cultivars.
The number of grains produced could be a useful indicator of
the number of flowers fertilized as well as conditions
required for setting and filling of grains. However, in this
study the number of grains was not indicative of total grain
yield, as in cultivars WL 711, WG 357, KSML 3 and WL 410,
the grain filling was incomplete. Even in dried ears, the
grains were only at half seed stage and appeared to be dry.
The inhibited translocation did not appear to be the only
reason for this effect because in that case, shrivelled but
complete grains were likely to be produced. Thus, in
addition to interrupted translocation, the grain development
was also incomplete. Thus cultivars TL 419, HD 2009, C 306
and WG 377 appeared to be relatively tolerant to Mn stress
implying that process of fertilization and grain development
were not much harmed by Mn stress. This would indicate
preferential utilization of Mn or capacity of the cultivars
to manage with limited supply of Mn.
Average Wt. of 100 grains (Translocation of assimilates to
the developing grains)
The average 100 grain wt. of cultivars increased
significantly with Mn application, but the differences among
5, 10 and 20 mg Mn/kg soil, were non-significant except C
306 at 20 mg Mn/kg rate (Table 5).
Under Mn stress condition, the maximum 100 grain wt. was in
cultivars WG 357 (low susceptible) and WL 410 (moderately
susceptible).
Thus in tolerant cultivars, the number of grains formed were
more (showing efficiency of fertilization) but the grain
weight was not correspondingly increased. This indicated
lesser availability of photosynthates than the sink
requirement in these cultivars. In less susceptible
cultivars (WG 357, WL 410) the number of grains formed was
low, the limited amount of photosynthates distributed among
lesser grains resulted in increase in grain weight.
Wardlaw (1968) and Bremner (1972) emphasized on the ability
of the individual grain to grow and precipitate
carbohydrates rather than the translocation as the major
determinent of seed growth. Asana (1974) advocated that
during the early stages of grain ontogeny when the
assimilates were not limiting, some inherent factor(s) must
be controlling the growth of grains which differed within
same ear as well as variety. Dua & Bhardwaj (1979) have
shown that variations among varieties with regard to 100
grain wt were traceable to endogenous auxin and cytokinin
production of the variety vis.a vis that of the ear. It is
imperative to study the varietal differences in content of
endogenous growth regulators in the flag leaf,
flowers/ears.
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