Vergara - 1976 - Physiological and morphological adaptability of ri

RESPONSE TO DEEP WATER STRESS 305
Temperature
35
PC)
~r| | I | | | |
MW Jm Jul 9w 5w Oct Mm Dec
2. Monthly air and water temperature at Supanburi.
Thailand, measured at U600 and 1200 hours, 1969-73
(data from the Royal Thai Inigation Department).
CULTURE OF FLOATING RICE
A brief knowledge of floating-rice culture might help to better understand deep
water stress. The ungerminated rice seeds are nonnally’ broadcast on dry soil at
6O to 130 kg/ha before the advent ofthe rainy season. Seeds germinate as soon as
sufficient rains have thoroughly soaked the soil In some areas. germinated seeds
are broadcast on puddied land. The seedlings grow under upland conditions for
4 to 20 weeks before the flood water comes. During this period of seedling
growth. tillering occurs and the rate depends a great deal on the ‘weed population
and availability of tvater. Oftentimes. drought may occur during this stage.
As the water level increases gradually; the rice plant also increases in length.
keeping abreast with the rise in water level. Inability to keep pace xvith the water
level may result in death of the plant. Many factors determine the survival of the
rice plant at this stage.
The rice plant may elongate to as much as 7 meters. usually fanning a mat on
top of the xvater surface. Branches and roots are formed on the upper nodes.
Uprootitig and snapping of branches are common in some areas. The varieties
are selected in such a way that panicle emergence occurs after the water level has
reached its peak or is receding.
Ilantesting is done after the flood tvaters have receded. although early maturing
varieties and occasionally the medium-maturing varieties are harvested from
a laoat.