THE PHOTOPERIOD IN SEVERAL VIETNAM VARIETIES OF RICE
ARMY BIOLOGICAL LABS FREDERICK MD
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The study of the light phase in three typical varieties of rice in North Vietnam by the method of the reaction to short and uninterrupted days showed the following The Nam Ninh variety, as the majority of varieties of spring rice with a short cycle of development, apparently is mildly sensitive to light conditions. It can bloom under the conditions of both the short and the uninterrupted day. The tenth and fifth month varieties--Tam Den and Chiem Chanh, with longer cycles of development, must have a short day for normal development. For the Tam Den variety, developing in the spring and summer under the conditions of a high temperature, the light phase begins very early--between the 20th and 23rd day following sowing, while for the Chiem Chanh variety, the development of which takes place first at a low winter temperature and then at a higher temperature in the spring and the beginning of summer, this phase begins much later -- only between the 90th and the 100th day following sowing. The temperature has a very important significance for the passing through of the light phase by rice. In the sinter months with a temperature of less than 20 degrees of heat, the Chiem Chanh variety does not enter this stage, in spite of the short day. For this it requires the higher temperatures of the spring months. The investigations shows that if under the conditions of North Vietnam rice is to be cultivated in the same area several times a year, then it is better to use varieties with shorter cycles of development, of the spring type, since they are more plastic, and become better adapted to various conditions of illumination.
- Agronomy, Horticulture and Aquiculture
- Anatomy and Physiology