Vergara - 1976 - Physiological and morphological adaptability of ri

3 l0 CLIMATE ANT) RICE
The floating-rice plant will continue t0 elongate with the increasing water
level as long as the panicles have not yet emerged. Htiwever. if the whole plant
is constantly submerged as a result ofrapid rise in the water level, the plant may
die.
Variety
Varietal differences in the ability to elongate are apparent since specific varieties
are planted in these deep water areas. These varieties are commonly known
as “floating“ varieties. Floating rice is significantly better in growth and yield
under deep tvater conditions than under usual field conditions. demonstrating
their distinct ivater-ttilerant nature (De Datta and Banerji. 1972). Floating varieties
grow much faster than riccs of similar durations, particularly in the early
tages of growth. and at later stages the whole plant leans over or lodges because
of height and spreading habit (Rarniah and Ramaswami. 1941; Yantasast et al.._
1970). Under submerged conditions. floating rice has higher carbohydrate content
and higher activities of amylase and invertase (Yarnaguchi and Sato. 1963).
The ordinary loii=land varieties dw not elongate as much
and so die when flood sets in for several days. Some intermediate experimental
lines. however, can elongate more than the ordinary lowland varieties when
subjected to shallow flooding, 100 to 150 cm (Jackson et al., 1972; IRRI. 1973).
These varieties are useful in marginal areas which may get inundated occasionally.
Abilay and De Datta (1974) showed that these varieties remain intermediatestatured
under ordinary conditions and will elongate only when subjected to
flooding. giwsing a relatively high yield tinder different ‘water-management
conditions (Fig. 3). The floating varieties, on the other hand. are relatively tall
even under tirdinary’ conditions. However. the floating habit or the ability to
elongate is a potential which will occur only when subjected to deep water
(Morishima ct al., 1959). Many wild species of rice have the ability to elongate
(Camus and Viguier. 1937'. Morishima et al, 1959'. Chowdhury‘ and Zaman,
1970).
MORPHOLOGICAL CHANGES RESULTING FROM DEEP WATER STRESS
Plant height
Since floating rice plants Will elongate much more than the depth of water.
plant height is not an indication of xvater depth. Plants have been reported to
elongate up to 600 cm (Alim et al.. 1962).
Elongation 0f internodes
Deep water rice is characterized by its ability to elongate under deep tlotiding.
and the elongation is mainly the extension of the internodes. Elongation of the
internode is the result of longer individual cells and more cells, mainly the latter
(Sugawara and Horikau-"a. 1971).