Agriculture Reference
In-Depth Information
sterility could be due to degeneration of embryo sac,
malformation of ovaries and deformation of young sporocytes
during meiosis (Fig. 26).
Non respective stigma
Low temperature
Fertilization failure
at flowering
Degeneration of embryo sac &
malformation of ovary
Fig. 26
Infl uence of low temperature at fl owering.
Since, the florets of rice are adichogamous, most of
the fl orets are self pollinated at the time of fl oret opening.
Synchrony between fl oret opening and anther dehiscence may
contribute to the high rate of self-pollination. However, the
synchronization is not always perfect and some rice fl orets
hybridize naturally. The rate of natural hybridization varies
among varieties of rice suggesting that there is a difference in
the reliability of self-pollination among varieties.
Rice pollination is susceptible to meteorological factors,
such as temperature. High temperatures at the time of fl owering
inhibit the swelling of pollen grains, whereas low temperature
at the booting stage impede pollen growth. The driving force
for anther dehiscence is the swelling of pollen at the time of
fl oret opening, temperature stress is considered to reduce the
percentage of anthers dehiscing at the time of fl owering. Thus
high (>35ºC) and low (<20ºC) temperatures result in poor
pollination and loss of yield (Table 14).
