• Volume 96, Issue 6

      December 1986,   pages  429-538

    • Effects of air pollutants on the growth and functioning of roots

      M S Kasana T A Mansfield

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      There is much concern in many parts of the world about long-term deposition of pollutants in soils, and especially the effects of ‘acid rain’. Less attention has been given to the indirect effects that two common air pollutants, sulphur dioxide and ozone, have on the growth of roots. There is now abundant evidence that both these pollutants cause changed patterns of translocation, so that more photosynthates are retained in the shoots and less transported to the roots. This can greatly affect root growth, and there are serious implications for various aspects of root physiology, symbiotic associations and water relations of the plant.

    • Population structure of tree species in forests as an indicator of regeneration and future stability

      S P Singh J C Tewari S Yadav P K Ralhan

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      The size class distribution in tree populations will continue to be used for analysing the regeneration of tree species and successional patterns in forest communities at extensive levels. However, information regarding the approximate estimates of lifetime expectancy (residence time) for each of the size classes, viz seedlings, saplings and trees, and the estimates of rate of net gain for them (population divided by residence time) can considerably enhance our understanding of the regeneration trends of species. It is shown that several population structures, based on size class distribution may indicate declining population trend, although the population, as indicated by rate of net gain parameter, in fact may foretell future expansion or stability. It appears that high species richness and high percentages of species with poor regeneration are interrelated with each other.

    • Physiology of foliar uptake of inorganic nutrients

      Seshadri Kannan

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      The leaves of terrestrial plants are capable of absorbing nutrients supplied in an aqueous medium. This capacity is exploited in many agronomic practices like application of herbicides, growth regulators and inorganic nutrients, for the purpose of enhancing crop production. The mechanisms of foliar absorption and subsequent transport of inorganic nutrients are discussed here. The penetration of the nutrient elements supplied to the leaf, through the outermost barrier—the cuticle—absorption by the leaf cells within, and transport from cell-to-cell finally to the conducting system of the leaf, are as complex as those following the root absorption. Yet, foliar supply of nutrients have many advantages over the root-feeding. There have been considerable interest in the practical use of this technique, as also several accomplishments not only in the understanding of the mechanisms involved in foliar uptake, but also in the development of chemicals and surfactants for the greater effectiveness.

    • Chlorophyll content in different plant species of Nagamalai hills and its significance on biomass production

      Kailash Paliwal T K Sivaraj K Natarajan M Peter Marian

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      Total chlorophyll content in leaves of 16 species in a foot hill of western ghats rich in herbaceous and shrub vegetation were determined. A correlation (r=0·7134) was made between the chlorophyll content and dry matter production.

    • Ontogeny of palmately compound leaves in angiosperms: 3.Arisaema Spp.

      K Periasamy E A Muruganathan

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      Arisaema is mono or bifoliar, exhibiting sympodial growth with annual conversion of the shoot apex into the floral apex. The shoot apex shows pendulum symmetry during successive plastochrons.

      Leaf initiation is hypodermal. The primordium quickly acquires the configuration of a 5 layered laminar plate meristem and its base extends around the shoot apex as the sheath. Following this, apical growth ceases in the primordium. Its apex becomes a hood like lamina wing and the sheath develops a median adaxial meristem which leads to its thickening. The lamina wing expends and becomes plicately folded at right angles to its surface. Each fold becomes a leaflet by the elongation of the abaxial edges and suppression of the adaxial edges of the folds. Early abortion of the lamina wing results in a scale leaf which comprises the sheath portion alone.

      An adult leaf has 300-400 veins which run independently from the corm to the leaflets through the petiole. The dorsal median strand develops first and goes to the midrib of the median leaflet. Subsequent strands arise laterally on either side of this in a series of tangential rows. Those of the first row bifurcate at the tip of the petiole to enter two neighbouring leaflets. The strands run parallel in the leaflet midrib and diverge at different levels into the lamina as lateral veins.

    • Gametogenesis, integuments initiation and embryogeny in three species of Habenaria (Orchidaceae, Orchideae)

      Sarvesh Kumar Sood

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      InHabenaria edgeworthii, Habenaria elisabethae andHabenaria galeandra the young anther wall consists of epidermis, endothecium, single middle layer and glandular tapetum. Tapetal cells are uninucleate and show dual origin. The microspore tetrads are linear, tetrahedral, decussate and isobilateral. At shedding the microspores are 2-celled. Ovules are anatropous, bitegmic and tenuinucellate. The development of embryo sac is of the Polygonum type. The primary endosperm nucleus degenerates. Development of the embryo in all the 3 species corresponds to the Onagrad type. The seed coat is formed entirely from the outer layer of outer integument.

    • Ecological studies on the rivers of Andhra Pradesh with special reference to water quality and pollution

      V Venkateswarlu

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      Ecological investigations in the rivers Moosi, Manjira, Tungabhadra, Kagna and Godavari have been made over a number of years. Physical, chemical and algal parameters were analysed at both unpolluted and polluted stations in the rivers and yearly averages, ranges and percentages of algae are presented. Bacteriological and biochemical conditions in the river Moosi are also described and discussed. On the basis of all these parameters, an assessment of water qualities and pollution is made. The significance of benthic algae in river monitoring and pollution studies is emphasized.

    • Effect of some growth regulators on the leaf architecture ofTagetes erecta L.

      Vidhu Y S Murty

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      Several leaf deformities viz bilobed leaf segment, asymmetrical leaf base, unsegmented simple leaves etc, accompanied with changes in leaf architecture were observed inTagetes erecta L. plants sprayed with aqueous solutions of different growth substances namely Indole-3-acetic acid, Gibberellic acid, 2,3,5-triiodobenzoic acid and Kinetin. The major changes include the gradual conversion of segmented simple leaf into an unsegmented one owing to 2,3,5-triiodobenzoic acid spray treatment.

    • GenusRamaria in the eastern Himalaya: subgenusLaeticolora-II

      R M Sharda K S Thind

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      This paper records 10 more taxa of the genusRamaria (Fr.) Bonorden subgenusLaeticolora Marr and Stuntz collected from different localities in the eastern Himalaya and adjoining hills.Ramaria synaptopoda, Ramaria rasilispora var.scatesiana, Ramaria sandaracina andRamaria suecica are new records for the Himalaya whileRamaria flaviceps var.cremea, Ramaria flavobrunnescens, Ramaria flavobrunnescens var.formosoides, Ramaria flavobrunnescens var.aurea, Ramaria obtusissima andRamaria camelicolor are being recorded for the first time from the eastern Himalaya. Type/authentic collections of the first 3 taxa have also been examined.

    • Effect of saline waters on drought affected cluster bean

      B K Garg S P Vyas S Kathju A N Lahiri

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      The influences of saline water irrigation of different concentrations (0, 40, 80 and 120 me l-1) were compared in droughted and undroughted plants of cluster bean (cv. FS-277) at its critical pre-flowering stage. Observations recorded on plant water status, diffusive resistance, nodulation behaviour and on different metabolic parameters (free proline, reducing sugars, starch and activities of N2-ase and nitrate reductase) after one and seven days of saline water irrigation revealed that the adverse effects were far greater in droughted plants revived with saline water, as compared to those which suffered only salt stress. These resulted in significant declines in growth and yield in the former as compared to the latter case, at all salt concentrations. The seed yield obtained in undroughted plants even under 120 me l-1, significantly exceeded the level of droughted plants revived with non-saline tap water. Since drought and salt stresses appeared to have cumulative adverse effects, it is proposed that irrigation with saline water at the critical stage, in the beginning of a dry spell, may be more rewarding than irrigation with saline waters at a belated stage when the plants have already suffered water stress. Salinity build-up in soil under this condition was not high.


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