• Volume 65, Issue 2

      February 1967,   pages  43-82

    • Effects of N:P ratios on the uptake of nitrate and phosphate by laboratory cultures ofTrichodesmium erythraeum (Ehr.)

      V D Ramamurthy S Krishnamurthy

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      The paper reports observations on the uptake of phosphate and nitrate by the Blue Green alga,Trichodesmium erythraeum, in axenic cultures with varying N:P ratios. The ratio of the increase of the phosphate absorption (Δp) to increase in phosphate concentration (ΔP) and also the ratio of increase of nitrate absorption (Δn) to increase in nitrate concentration (ΔN) were determined. Increase of concentration of phosphate in the medium increased the rate of absorption of phosphate but had no effect of nitrate absorption. Increase of concentration of nitrate had a positive influence on both nitrate and phosphate absorption. In media with N:P ratios ranging from 20:1 to 20:5 the Δp/ΔP was 2·1. With N:P concentration of 20:10 in the medium the Δp/ΔP was 0·9, and in media with N:P ratio 20:15 it was 0·1. With regard to effect of nitrate in media with N:P ratios ranging from 1:1 to 15:1, the Δn/ΔN was 0·29 and Δp/ΔP was 0·06; in media of 20:1 to 25:1 Δn/ΔN was 0·67 and Δp/ΔP was 0·1. The coefficient of cell increase (K) did not show any appreciable change with increase of concentration of either N or P in the medium.

    • Embryological studies in the bromeliaceae - I.Lindmania penduliflora (C. H. Wright) stapf.

      K K Lakshmanan

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      Embryological characters ofLindmania penduliflora is presented. Anther tapetum is of the secretive type and the cells are binucleate. Microspore mother cells divide in a successive manner resulting in isobilateral, tetrahedral or linear tetrads. Mature pollen grain is two-nucleate. Division of the single hypodermal archesporial cell results in a primary parietal cell and a megaspore mother cell. Meiotic division of the latter results in a linear tetrad. The chalazal megaspore of the tetrad develops into a normal type of eight-nucleate embryo-sac.

      Endosperm is of the helobial type. The chalazal endosperm nucleus may divide, with or without wall formation, either synchronised with the division of the micropylar endosperm nucleus or else earlier.

    • Observations on the floral morphology and embryology ofUtricularia stricticaulis stapf

      G Shivaramiah

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      The present paper deals with some aspects of floral morphology and embryology ofU. stricticaulis.

      The inflorescence is a raceme. Flowers are large, bisexual, zygomorphic. Ovary is superior, bicarpellary, unilocular and contains numerous anatropous ovules on central massive placenta.

      The anther is tetralocular having 4-layered walls, with fibrillar endothesium and glandular tapetum. Microspores are tetrahedral and decussate. Pollen grains are tetraporate and 3-nucleate at the time of shedding.

      Ovules are unitegmal, tenuinucellar. A well-developed integumentary tapetum is restricted to the central part of the embryo-sac.

      A single hypodermal archesporial cell directly functions as the megaspore mother cell. The tetrad is linear and chalazal megaspore functions.

      Development of embryo-sac conforms to the Polygonum type. The endosperm isab-initio cellular. The micropylar chamber formed after the first division of the primary endosperm nucleus gives rise to binucleate micropylar haustorium, from the chalazal chamber, the chalazal haustorium develops, which is also binucleate.

      The embryogeny follows the solanad type.

    • Some observations on the autecology ofThemeda quadrivalvis (Linn.) O. Ktze. Var.Quadrivalvis

      S C Pandeya

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      Themeda quadrivalvis var.quadrivalvis has restricted geographical distribution. It, otherwise, dominates in low-lying areas at Sagar, M.P. (where the studies were undertaken). The grass community is kept fenced during the growth period. Underlying soils are stabilised, and moderately moist. The study reveals that the restricted distribution of the species is perhaps due to low migration capacity and low ecological amplitude. Success of the species to form almost pure stands, in its area of distribution, may be due to almost no seedling mortality and formation of simple aggregates. Further, the species yields a good bulk of hay. It has optimum feed value during the month of September.

    • Reproductive and nutritional cycles of the crabPortunus pelagicus (Linnaeus) (Decapoda: Brachyura) of the Madras coast

      A Abdul Rahaman

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      The gonadal and hepatic indices were determined. Even though the crabPortunus pelagicus is a continuous breeder, there appears to be three maximal periods of development of the gonad and hepatopancreas. The gonad index is high in the months of November-January and June and the hepatic index shows the greatest development in the months of November-January and August. There appears to be a direct relationship between gonadal and hepatopancreatic development. These results have been discussed in the light of previous work.

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