• Volume 48, Issue 1

      July 1958,   pages  1-63

    • Studies on theBracon hebetor-brevicornis complex (Hymenoptera: Braconidæ)

      E S Narayanan B R Subba Rao A K Sharma

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      This work discusses the views of various authors as to whetherBracon hebetor (Say) andBracon brevicornis (Wesmael) are two separate species.

      The fairly detailed studies made during the course of the present investigations in regard to the antennæ, the external male genitalia and the experiments conducted to find if the two forms successfully mated to give rise to a progeny consisting of both males and females, have been made. The inequality in the number of antennal segments in the individuals has been studied in detail. It is suggested that there is a complex of more than two species and only a thorough cytological study could solve the problem.

    • Studies on the nutrition of rice plant (Oryza sativa L.) - Part II. A comparative study of nitrogen requirement ofIndica andJaponica varieties of rices

      A Tanaka S Patnaik C T Abichandani

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      Comparative efficiency of a short durationindica variety (Ptb 10) and ajaponica variety (Aikoku) has been tested under increasing nitrogen levels in water culture trials. Theindica variety does well at 20 p.p.m. of nitrogen, but at higher nitrogen levels the grain yield is pulled down. Thejaponica variety on the other hand grows well at nitrogen levels of 60 p.p.m. and there is no appreciable decrease in grain yield even at 150 p.p.m. nitrogen. Thejaponica variety however fares very badly at nitrogen levels of 20 p.p.m. and less and the grain yield at these levels is even poorer than that of theindica variety.

      Efficiency of nitrogen utilization by two varieties has been measured by the ratio of soluble to protein nitrogen in the plant both at vegetative and reproductive stages. There is no difference in this ratio of the two varieties at the vegetative stage. At the reproductive stage however, theindica variety has a higher ratio of soluble to protein nitrogen both at 60 and 150 p.p.m. nitrogen than that of thejaponica variety, showing a disturbed nitrogen metabolism ofindica under high manuring condition. The depression of the grain yield ofindica at higher nitrogen levels is also seen to be due to decrease both in the number of filled grains per panicle and weight of 1,000 grains, factors which are mainly decided at the reproductive stage. It is therefore concluded that the nitrogen metabolism ofindica gets disturbed at the reproductive stage due to excess nitrogen level and the variety is not able to utilise nitrogen efficiently for formation of grain. Thejaponica variety however, utilises nitrogen efficiently under high manuring conditions and gives greater yield.

    • Carbon-nitrogen metabolism of soil fungi - V. Role of cyanide, nitrite and sulphur

      S Natarajan

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      Fusaria reduce nitrates to nitrite and ammonia irrespective of the carbon source. Fusaria possess potassium cyanide insensitive nitrate reductase.

    • The cyto-architecture of the yeast nucleus

      Saraswathy Royan

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      1. A well-defined nuclear membrane enclosing formed structures could be observed in the living cells ofSaccharomyces cerevisiæ (NRRL, Y-567) from 120–168 hr. wort cultures, under ordinary, phase contrast and dark ground illumination.

      2. The formed structures within the nuclei correspond to the chromocenters and not the nucleoli of higher organisms.

      3. A comparison of Feulgen and Hæmatoxylin stained preparations renders possible the differentiation of a pair of bodies lying within a nuclear membrane from a bi-nucleate stage.

      4. Iron hæmatoxylin preparations in which the vacuolar membrane has separated from the cytoplasm confirm the extra-vacuolar position of the nucleus.

    • ElectricalVersus chemical theory of neuromuscular transmission

      Inderjit Singh A K Acharya

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      1. Unstriated muscle shows two kinds of responses; one kind is produced by electric current and the other by chemicals such as potassium or acetylcholine.

      2. Certain reagents affect these two kind of responses differentially.

      3. In dog’s stomach muscle, the responses produced by electric current are inhibited by tone-producing substances such as bromide, nitrate, iodide, thiocyanate. The responses to chemical stimulation are potentiated. The response to nervous stimulation are inhibited. It is concluded, therefore, the response produced by nervous stimulation is produced by electric current, and that can only be the action potential.

      4. Excess of calcium potentiates the response to nervous stimulation, acetylcholine and potassium, but inhibits that to electric current. So it is concluded that the response due to nervous stimulation is also due to liberation of a chemical substance, presumably acetylcholine.

      5. Neuromuscular transmission in unstriated muscle is therefore electro-chemical, produced both by the action potential of nerve and liberation of a chemical substance. The former produces the initial response, and the latter sustains it, and imparts to it, tonic properties.

    • A chromosome survey of indian dioscoreas

      R Sundara Raghavan

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      The present paper deals with the chromosome numbers of nine species of wild and cultivated Yams. Five species, namely,D. pubera, D. deltoidea, D. hispida, D. belophylla andD. esculenta, have been worked out for the first time. InD. alata andD. bulbifera different chromosome races for the Indian forms have been recorded besides the ones reported by previous workers. It is interesting to observe that the Japanese races ofD. oppositifolia andD. pentaphylla are higher polyploids than the Indian forms reported here.

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