Vergara - 1976 - Physiological and morphological adaptability of ri

sTRRILE-TYPR cool. mnrm‘ IN mom’ RICE PLANTS 291
Fertility 1%)
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d a
Auricle distance tun]
4. Difference in sterility from cooling treatment at the
different pollen developmental stages of the third spikelets
on the uppermost primary branches (Satake and
Hayase. 1970). Auricle distances were measured at the
start of cotiling: L’ Z: lc2pl(1l€flt-:'~Z_\’g0I€llBL P Di
paehytene- diakiitesis; M: 1st and 2nd divisions; T:
tetrad; (1,: lst contraction phase: Rn lst recovery
phase; C_.: 2nd contraction phase; R_-: 2nd recovery
phase. —.—l : range of progress of pollen developmental
stage during each treatment in Norin 20.
treatments. He noticed that the tapetal abnormalities centered in anther loculi
during the period from tetrad to the first contraction phase. This led us to consider
that the growth and development stage from tetrad to young microspore
is the most sensitive to both the microsptires and tapetal cells.
MECHANISM OF STERILITY
Cytological injuries during coolness
Since Sakai (1937b), earlier workers have observed the microscopical abnormalities
in the anther loculi l day after the initiation of cooling treatment. Sakai
(194921) showed that the percentage of tapetal hypertrophy" increased as temperature
lowered. The rate of tapetal hypertrophy by cooling treatment was
closely" correlated with varietal resistance to sterile-type cool injury. Thus he