Volume 57, Issue 3
March 1963, pages 149-208
pp 149-163 March 1963
pp 164-177 March 1963
pp 178-194 March 1963
Chlorophyll, ascorbic acid, free reducing sugars and total manganese were highest in the least susceptible variety N.P. 15 and lowest in the most susceptible N.P. 24. In the latter, total carbohydrates were more in the root than in the shoot, while in the former, the opposite trend was observed. Fe/Mn ratio was found to increase with increasing susceptibility. Under pathogenesis, there was progressive reduction in the contents of manganese, leaf pigments, ascorbic acid and total carbohydrates and an increase in the iron content, Fe/Mn ratio and free reducing sugars in N.P. 24 whereas in N.P. 15, although there was a reduction in leaf pigments and total carbohydrates, such a derangement was not apparent in the case of ascorbic acid and free reducing sugars. Transpiratory studies showed that there was an increase in the rate of transpiration during the early stage of the disease which was found to fall off gradually with the advancement of infection. The possible role of ethylene in wilt pathogenesis is discussed.
pp 195-208 March 1963
1. The anatomy and histology of four species of polychaetes,viz., O. erimita, L. medusa, G. embranchiata andC. insecta are given.
2. The nephridia inO. erimita, L. medusa and inC. insecta are of the mixonephridial type while inG. embranchiata it is of protonephromixial type with simple solenocytes performing the function of excretion. There is a pair to each segment in the former two species excepting in the few anterior and posterior segments. But inL. medusa there are only three pairs and inC. insecta four pairs.
3. The blood supply to the nephridia and the extent of the excretory surface to the length of the worm are given. Both in blood supply and in the excretory surfaceC. insecta showed the maximum development.L. medusa, O. erimita andG. embranchiata showed lesser grades of development in the order mentioned.
4. The differences in the blood supply the nephridia receive and in the extent of the excretory surface to the length of the worm have been argued as due to the different capacities for osmotic regulation as reflected by volume regulation. Taking this a measure their distribution in a brackish-water environment has been explained.