• Volume 99, Issue 5

      October 1989,   pages  405-515

    • High frequency somatic embryogenesis and plant regeneration from immature inflorescence cultures of two Indian cultivars of sorghum (Sorghum bicolor L. Moench)

      Leela George Susan Eapen P S Rao

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      Somatic embryogenesis and subsequent plant regeneration were obtained from immature inflorescence segments of two cultivars ofSorghum bicolor L. Moench. Callus was induced on Murashige and Skoog’s medium supplemented with 2,4-dichlorophenoxyacetic acid (2 mg/l) and zeatin (0.1 mg/l). Transfer of calli to Murashige and Skoog medium alone or with reduced level of auxins with or without cytokinins resulted in the production of somatic embryos and plantlets. The combination of a cytokinin with Triiodobenzoic acid promoted the highest number of somatic embryoids. The best response was obtained from inflorescences 10–25 mm in length. Regenerated plants were transferred to field for further evaluation.

    • Epicotyl excision and reserve mobilization in winged bean

      T Kamala Devi K Sreekumar K N Madhusudanan

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      Epicotyl excision of dark-germinated winged bean (Psophocarpus tetragonolobus (L.) DC) resulted in the development of a lateral each at the cotyledonary axils. The availability of this ‘2-shoot system’ permitted evaluation of the interaction between the rowing parts and the storage tissue in which some alterations had already been initiated to support the growth of the primary axis. Starch level was lowered in the 2-shoot system, in particular in the laterals and the radicle. The pair of laterals had significantly higher sugar content than the control plumule, without alteration in the distribution among the component sugars. Epicotyl excision resulted also in the accumulation of dry matter and sugar in the radicle. Although seedling decapitation led to increased investment of dry matter in the growing parts, the greater part of dry solids and starch and a major part of sugar were retained in the massive cotyledons.

    • Xylotomical studies of some Boraginaceae

      S xxxV R Surya Kamala B Hanumantha Rao K V Ravi Kumar

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      Xylotomical features ofTournefortia rugosa, Tournefortia caracasana, Heliotropium angiospermum andMallotomia gnaphalodes of the family Boraginaceae have been described with emphasis on vessel elements, fibrous elements, parenchyma and vascular rays. Presence of helical thickenings in the narrow vessels, septate fibres, siliceous granules, crystals, tannins and druses in the ray cells are some of the interesting features met with in these members.

    • Optical microscopic studies on the structure and secretion of resin glands in some Apocynaceae

      R B Subramanian V Murugan J S S Mohan J A Inamdar

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      In some Apocynaceae a group of 10–15 resin glands is present as finger-like projections on the adaxial side of the proximal end of the petioles and sepals or petals. They originate from a group of epidermal and sub-epidermal cells. At maturity the glands are differentiated into a short stalk and a clavate head. The latter is composed of epidermal secretory cells and sub-epidermal parenchyma. Structurally and ontogenetically the resin glands resemble extrafloral nectaries and the standard colleters of the Rubiaceae. However, histochemical tests for lipophilic substances revealed that these glands secrete resin. The pale yellow, viscous secretion is released by cuticular bursting and covers the tender shoot apices and developing buds. The position and the secretory activity of the resin glands in relation to their function is discussed.

    • Leaf dynamics of early versus late successional shrubs of sub-tropical moist forests of north-eastern India

      U Baruah P S Ramakrishnan

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      The two early successional shrubs (Melastoma malabathricum L. andMussenda frondosa L.) are periodic growth leaf-exchanging-types (leaf fall is associated with bud break; leaf span of leaves being approximately 12 months), whereas the two late successional ones (Litsaea khasiana Meissn andOxyspora vagans Wall.) are periodic growth evergreen types (leaf fall is completed well after bud break; life span of leaves being a little over one year). Early successional shrubs have larger leaf production and faster turn-over rates, unlike late successional shrubs with production confined during the early part of the growing season (April–May) is geared to expose larger area over a longer time period, for survival under shade. The early successional shrubs have an exploitative strategy whereas the late successionals are conservative in nature for survival under shade.

    • Mycoflora associated with stored wheat and its milling fractions in India

      Indra K Kunwar

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      The fungi associated with stored wheat grains (38 samples) and their milling fractions (52 samples) were isolated from samples collected from several locations in India. Samples were screened by Dilution plate method and incubated at 10, 25, 37 and 55°C. Aspergilli were isolated from all the samples whereas Penicillia, other imperfect fungi and Mucorales were found in 83, 62 and 50% of the samples respectively. ThirtyAspergillus spp., 27Penicillium spp., 32 species of other imperfect fungi, 17 species of Mucorales and two species of Ascomycetes were isolated. Frequently occurring species from various groups wereAspergillus flavus, Aspergillus fumigatus, Aspergillus candidus, Aspergillus versicolor, Penicillium urticae, Penicillium islandicum, Penicillium cyclopium, Cladosporium herbarum, Curvularia lunata, Alternaria alternata, Mucor lausannensis, Absidia lichtheimi, Rhizopus arrhizus andSyncephalastrum racemosum.

    • Splash dispersal inColletotrichum graminicola (Ces.) Wilson, the causal organism of anthracnose of sorghum

      A H Rajasab A Ramalingam

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      The conidia ofColletotrichum graminicola (Ces.) Wilson were dispersed only by rain drops. The dispersal was related to the frequency of rainfall. Under field conditions, conidia were dispersed vertically up to a height of 0·75 m and laterally up to a distance of 1 m from the source. Both incident water drops and flowing water liberated conidia from the sporulating lesions. Peak liberation of conidia occurred with the water drops 3–11, and most conidia were removed from the sporulating lesions within 60 s, suggesting dispersal of the pathogen even during small showers of rain.

    • A cytoembryological study ofUrochloa panicoides P Beauv. (Poaceae)

      Basa Vaiah T C S Murthy

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      A comparative study of microsporogenesis, megasporogenesis and female gametophyte development inUrochloa panicoides var.panicoides, var.pubescens, var.marathensis and var.velutina has been made. In all these varieties gametic chromosome number is n=24. Meiosis in pollen mother cells is normal and characterised by the regular incidence of 24 bivalents and their regular disjunction. This has resulted in high pollen fertility. Occassionally occurring two univalents in var.panicoides and one tetravalent in var.velutina are the only abnormalities observed. In all the varieties, the ovules are bitegmic, pseudocrassinucellate and hemianatropous. A single hypodermal archesporial cell differentiates in the nucellus and directly functions as megaspore mother cell. It undergoes meiosis forming usually a linear, rarely T-shaped tetrad. The chalazal megaspore after 3 nuclear divisions forms an 8-nucleate embryosac. The mature embryosac is spindle shaped, consisting of an egg apparatus, 2 polars and 3 antipodals. In var.panicoides and var.pubescens the antipodals divide to form 6–12 celled antipodal complex, whereas in var.marathensis and var.velutina they just become binucleate and hypertrophied. The mature embryo conform to panicoid type. The results are discussed in relation to the systematics of these sexually reproducing taxa.

    • Comparative studies on the toxicity of petroleum oils and their aqueous extracts towardsAnabaena doliolum

      J P Gaur A K Singh

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      Assam crude, kerosene, petrol, diesel and furnace oil administered into the culture suspension ofAnabaena doliolum as whole oil or aqueous extract exerted concentration dependent toxic effects. The hierachy of toxicity of the test oils was diesel > furnace oil > petrol > kerosene > crude. The oils rich in aromatics were most toxic and therefore estimation of this fraction might enable prediction of toxicity of an oil. Growth rate was a more sensitive criterion of oil toxicity as compared of final standing crop. In case of crude and kerosene, the whole oil application was more inhibitory than their respective aqueous extracts, whereas reverse trend was obtained in case of other oils. The study recommends toxicological evaluation of whole oils as well as their aqueous extracts for meaningful results.

    • Observations on unusual akinete formation inAnabaena azollae in isolation culture

      B S Vaidya Johny Thomas

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      An unusual type of akinete formation was observed in cultures ofAnabaena azollae which were not reported in any other cyanobacterium earlier. These akinetes were spherical comparatively larger than the normal ones and covered with a thick inner and thin outer envelopes. It represented transformed vegetative cells which faced temporary growth difficulties in non symbiotic conditions. The germination of the akinete started with an enlargement followed by the division of the cell contents into numerous fragments. Later the each divided cytoplast underwent 3 to 4 divisions and developed into a group of interwoven trichomes.

    • Decomposition studies on two floating leaved macrophytes,Nymphaea nouchali andNymphoides indica, of lake Kondakarla, India

      K S N Murty V Seshavatharam

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      Rates of weight loss and nutrient release (N, P, Ca, Mg, Na, K) were measured in decomposing tissues ofNymphaea nouchali Burm (leaf and rhizome) andNymphoides indica (L.) O Kuntze under field (90 days) and laboratory (60 days) conditions. Dry weight loss followed the sequence ofNymphoides indica>Nymphaea nouchali leaf >Nymphaea nouchali rhizome. The rate of nutrient release (N, P, Ca, Mg) from the decomposing tissues ofNymphaea nouchali rhizome appears to be correlated with nutrient concentration in leachate (receiving water) under laboratory experiments. The concentration of nitrogen in the decomposing tissues of all the samples increased with time. No increase in sodium and potassium concentrations was observed during the study under both the conditions. The maximum elemental loss was mostly observed under laboratory experiments than in the field studies. Accumulation of nitrogen, calcium and magnesium instead of release at certain stages of decomposition is attributed to microbial immobilization. The sequence of elemental loss in the decomposing tissues of these macrophytes is Na>K>P>Mg>Ca>N.

    • Seasonal patterns of phytoplankton biomass and productivity in a tropical estuarine complex (west coast of India)

      V P Devassy J I Goes

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      Phytoplankton cell numbers and chlorophylla determinations were made during the premonsoon, monsoon and postmonsoon periods in the Mandovi-Zuari estuarine complex (west coast of India). Primary productivity estimates agreed well with chlorophylla and phytoplankton cell numbers. The consequent decline in salinity with the onset of monsoon was found to be an important factor controlling the distribution, abundance and productivity of phytoplankton. As compared to the Zuari estuary, the Mandovi retained typical estuarine conditions and a greater phytoplankton biomass. Based on primary productivity estimations, the potential fishery resource of this estuarine complex has been computed.

    • Anaerobic digestion of alkali treated crop residues with cattle waste

      Gh Hassan Dar S M Tandon R Singh

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      In laboratory scale batch digesters various alkali treated crop residues with cattle waste showed 17–31% more biodegradation than did cattle waste alone. Higher biogas production (405–445 ml g−1 volatile solids fed) was obtained with crop-cattle waste mixtures than with cattle waste alone (343 ml g−1 volatile solids fed) in 35 days digestion at ambient temperature (30±1°C). The biogas showed maximum methane, after the digesters became stabilized, from lantana (57%), followed by wheat and other plant residues codigested with cattle waste (53–54%) in comparison to cattle waste alone (51%).

    • Pollination mechanism inCoriandrum sativum Linn. (Apiaceae)

      A K Koul I A Hamal S K Gupta

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      Exposed nectar, abundant pollen production, zygomorphic flowers and compact umbels are the contrivances which attract in large numbers a wide variety of insect species to coriander flowers. Some of these visitors carry coriander pollen from one flower/umbel to another and by so doing act as potential pollinators; others are only casual visitors.

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