Agriculture Reference
In-Depth Information
of low germination rate at low temperature. The reduction
in seedling growth of rice due to low temperature is one of
the major problems in tropical and sub tropical areas at high
altitude as well as areas where cold mountain water is used
for irrigation. In such areas, water temperature during sowing
is below 15ºC, whereas the optimum range for germination
and early seedling growth of rice is 25-30ºC. The delay in
seedling emergence due to cold water, greatly increases
seedling mortality and causes serious decreases in yield and
increases competition with weeds. In many Asian countries,
the direct seedling culture has become increasingly important
in rice growing areas. Therefore, vigorous germination at low
temperature is an important character for establishment of
stable seedling in direct seeding culture where rice is sown
directly in to fl ooded fi elds (Liang et al. 2006).
Changes in the content of starch, protein and RNA and
in the activity of their hydrolases in the rice endosperm were
determined during the fi rst week of germination both in the
dark and in the light, changes were generally more rapid in
the dark than in the light. Oxygen uptake and RNase activity
started to increase and the root protruded on the second day,
followed by the coleoptile on the third day, and the primary
leaf on the fourth day (Table 2).
ATP level was at a maximum on the fourth day. The activity
of amylases and R enzyme increased progressively, but that of
phosphorylase tended to increase during starch degradation. A
new α-amylase isoenzyme band appeared during germination.
Table 2
Organ differentiation in germinating rice seed.
O
rgan differentiation
Days after germination
Root
Second
Coleoptile
Third
Primary leaf
Fourth
