Vergara - 1976 - Physiological and morphological adaptability of ri

RICE (iROWFH IN DIFFERENT EI\'\"IR()NI\»"II:‘.N'I'S 431
Tillers trio/rill]
4O
3O
tllllv
slugs
Muitlmum
-
II-lflbll
Dry weight.
I50
(q/niu)
Weeks utter transplanting
l-i Active -——-t-—Lnq i-l-Repruducfiva-l- Rioeninq —-l
WM“
Vegetative qmwth
l. Example of growth process of tropical rice (Peta in
the rainy season at iRRI).
formula because of (a) the seasonal fluctuation of environmental conditions.
which is often irregular and unpredictable, and also of (b) the development of
growth phases.
The tintogenesis of the rice plant is generally considered to consist of three
phases. i.e. vegetative, reproductive, and ripening (lshizuka and Tanaka. 1954).
Figure l is an illustration ofthe growth process (Tanaka et al., 1964).
Definition and characteristics 01‘ each growth phase follmv.
The vegetative phase is from germination to the panicle-primordia initiation
stage (initiation of most of the tillers). After germination. leaves come out one
after another. The lcafing interval is almost constant under a given condition.
The leafing interval is shorter and each leaf is larger when the temperature is
higher. and also when the nutrient status is better. During this phase. tillers come
out with the growth. The rate of tillering is faster when temperature is higher.
and also when the nutritional status is better. Tillering is closely associated with
the nitrogen content o1‘ the plant. which is influenced by the availability of nitrogen
in the soil and by the capacity ofplants to absorb nitrogen. An increase in
planting density naturally results in an increase of the tiller number per unit of
field area. (‘renerallit the internode does not elongate during this phase. Vegetative
growth terminates at the panicle-primordia initiation stage, and its duration
varies greatly with the combination of (a) varietal character. such as the duration
of the basal vegetative phase and photoperiod responsiveness. and (b) climatic
conditions. such