Cultivation and ecophysiology of rice plants in the tropics. III. Photosynthesis of rice cultivars of india, measured by the Tsuno's simple method.

Abstract

Photosynthetic activities of four rice cultivars of India was investigated by employing a new method deviced by Tsuno. The improved cultivars Vijayamahsuri, Sonamahsuri, HR 35 and HR 59 and the local scented cultivar Basmati were used. The temperature optimum for photosynthesis was found to be 38°C in all cultivars in the experiment done by the new method. Cultivars Vijayamahsuri and Sonamahsuri had a relatively high ability to photosynthesize under low light intensities. The chlorophyll content of the leaves affected significantly the rate of CO2 uptake. Photosynthetic activity of the leaf differed not only with the cultivar but also with its position on the culm. At the ripening stage the flag leaf in cvs. Vijayamahsuri and HR 35 showed the highest photosynthetic capacity, whereas in cv. Sonamahsuri the second and third leaf assimilated greater amounts of CO2 than the flag leaf did. A close correlation was found between the chlorophyll content and the photosynthetic ability of the leaf, when pooled for all the upper three leaves of four cultivars, except for the case of leaves in cv. HR 59 with only a slight difference in chlorophyll content. We considered that the method deviced by Tsuno and newly introduced here will be available for the test of photosynthetic activity of crop plant, especially for the researches dealing with a great number of materials.