• Volume 70, Issue 4

      October 1969,   pages  157-191

    • Diel cycle of dissolved carbohydrates in two freshwater ponds

      Sumitra Vijayaraghavan P Navaneethakrishnan R George Michael

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      Diurnal changes of the dissolved carbohydrates in relation to fluctuations in plankton content and primary productivity were investigated in two freshwater ponds. The highest amount of DCHO recorded was 52·25 mg/litre which appears to be high as compared to those of temperate waters. The amount of carbon released in DCHO usually exceeded that of the carbon assimilated during photosynthesis. It has been suggested that probably factors such as temperature, pollution and bacterial activity are responsible for the high yield of dissolved carbohydrates.

    • Studies on the causes for seed failure in the intergeneric cross between sugarcane and maize

      N Hrishi S Marimuthammal L D Vijendra Das

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      The causes for seed collapse or failure in 32 crosses between different clones of sugarcane and maize were investigated. The pollen germination studies indicated considerable selective responses of the pistils of different clones to maize pollen. Though blocks to crossability were present in the styles of a few clones, 87 per cent. of the clones, employed as pistillate parents, did respond favourably to maize pollen, thereby increased the chances for abundant fertilization. Though fertilization occurred, the embryos degenerated for want of nourishment from the endosperm. The failure of the primary endosperm to develop further could be attributed perhaps to somatoplastic sterility or due to the unbalance of gene dosage obtaining in the primary endosperm.

    • Occurrence of larvae ofPseudorhombus elevatus Ogilby (Heterosomata—Pisces) along the South-West Coast of India

      C B Lalithambika Devi

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      Larvae ofPseudorhombus elevatus Ogilby ranging in standard length from 3·47 to 7·76 mm. are described. These were brought on board R. V.Varuna in the vertical plankton haul collected during the international Indian Ocean Expedition 1962–65 from two stations off the South-West Coast of India. Larvae slightly less than 8 mm. had developed the full complement of dorsal, anal, caudal and pelvic rays but lacked pectoral rays and a few gill rakers. Metamorphosis must take place at a small size, probably at less than 10 mm. standard length. The most notable character of middle and late stage larvae is the pronounced elongation of the nine anteriormost dorsal fin rays. Adults ofP. elevatus Ogilby with mature gonads were subsequently collected from the same region. The identification of the larva to species is based mainly on meristic characters.

    • Distribution of iron in the tissues of some bivalve molluscs

      S Krishnamurthy

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      The quantitative distribution of iron in the tissues has been studied in three species of bivalves. Two of these,Arca granosa andArca inaequivalvis possess haemoglobin in their blood corpuscles, whereas the third species,Meretrix casta, which has been investigated for comparison, does not possess haemoglobin. The concentration of iron in the digestive diverticula ofArca is considerably higher than in the other tissues and also than that in the digestive gland ofMeretrix. The relatively high concentration of iron in the digestive diverticula is similar to that in the haemopoitic organs of vertebrates. This would suggest that the digestive diverticula ofArca have possibly a role similar to that of the haemopoitic organs.


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