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Thesis Summary



TITLE:

          Air pollution effects on the structural, pharmacognostical and phytochemical traits of the barks and leaves of Azadirachta indica A. Juss and Dalbergia sissoo Roxb "

Subject : Botany
Faculty : Science
Name of the student : AB. Rashid Trag
Name of the supervisor : Dr. T. O. Siddiqui
Name of the Co-supervisor : Dr. Mahmooduzzafar
Date of Viva Voce : 12th December 2002


Summary

          This study was carried out on Neem (Azadirachta indica) and Sheesham (Dalbergia sissoo) trees grown abundantly around the Badarpur Thermal Power Plant where atmosphere is polluted due to coal-smoke pollutants emitted from the stacks of the power plant. The observations were carried out for three consecutive years. Plant materials (mature leaves) collected from five selected sites, located at different distances from the pollution source, were studied and analyzed so as to assess the impact of environmental degradation on anatomical, physiological, biochemical, pharmacognostical and phytochemical traits of the test plants.

          The SO2, NO2 and SPM (Suspended Particulates matter) concentrations were maximum at site III, whereas site V had the minimum stress (comparable with the non-polluted atmosphere) and was, therefore, considered as the reference site.

          The soil was slightly alkaline sandy loam at all the sites. Nitrogen content of the soil was minimum at the highly polluted site (site III), and maximum at site V. Soil sulphur was low at sites I and IV. Potassium in soil was lowest at the most polluted site.

          The length and width of phloem fibres, seive tube elements, relative proportion of seive tubes and fibres, amount of conducting phloem and the vascular tissues in the petiole of leaf of both species decreased at all sites in all seasons. However, proportion of axial parenchyma and ray parenchyma of conducting phloem in the stem increased.

          The net photosynthetic rate and stomatal conductance of leaves declined at the polluted sites but the intercellular CO2 concentration increased.

          The nitrate, sugar and sulphur contents of leaf and secondary phloem enhanced at almost all sites, with the maximum enhancement at site III. However, the reduced nitrogen, reducing sugar and sulphate contents in both leaves and bark decreased at all sites.

          The pharmacognostic parameters varied with respect to pollution. Loss on drying, per cent ash value content, water-soluble ash, sulphated ash and acid insoluble ash contents were enhanced with respect to pollution load. The various extractive values increased at various distances from the pollution source. The maximum increase was recorded at 8 km from the pollution source. However, the petroleum ether extractive decreased with respect to site V.

          Tannin content decreased proportional to the pollution load in case of A. indica.

          Reduction in the crude fibre was also observed. The protein content (crude protein) declined under pollution stress in both A. indica and D. sissoo.

         Several compounds, mostly flavonoids, terpenoids and fatty acids, were isolated from the barks of A. indica and D. sissoo. Their amounts declined under pollution stress.

         Flavonoid content in the leaves of both the trees also reported decreased.

         Few new compounds were isolated through column chromatography in order to mark them as reference or marker compounds for quantitative estimations.

Compounds isolated from the bark of A. indica are;

  • RN-I 5-methyl-n-triacotane.

  • RN-2 n-heptacosan-8-ol

  • RN-3 n-hexacosanoic acid

  • RN-4 2,6,10,14-tetramethyl-pentadeca-8-en-2, 7-diol

  • RN-5 2,6,10-trimethyl-14-cyclopentanyl-n-tetradecan-6a-ol

  • RN-6 5,7-dien,3b-ol-b-D-glucopyranoside

  • RN-7 9,9-dimethyl-decan –7-en-2-ol-11,12-dioic acid

  • Compounds isolated from the bark of D. sissoo are;

  • RD-I n-hexacosa-5-ol -yl propionate

  • RD-2 n-tetracosa-5-ol -yl propionate

  • RD-3 6-hydroxy-7-methoxy-4-(2’-hydroxybenzyl)-benzopyron

  • RD-4 9,11,12-trihydroxy-10-methoxyanthracare-14,17-[2H]-pyran

          Plants have a greater capacity to accommodate very wide fluctuations in their environment but the buffering capacity they endow finally fails, resulting in chronic sub-optimal growth. The recorded accumulative toxic effects of pollution in the morphological, physiological, biochemical and phytochemical characteristic are suitable indicators for biological monitoring. The pollution load alter, not only the quantity but also the quality of active compounds of the trees, thereby decreasing the therapeutic value of a compound or a combination of compounds. The maximum effect was observed during winter, confirming that the test species were more sensitive to pollution during winter.