Published under the author's permission

STUDIES ON SOME INORGANIC ELEMENTS

IN THE LEAVES OF HALOPHYTES

FROM THE SUNDARBANS (WEST BENGAL)



SAUREN DAS AND MONORANJAN GHOSE
Agricultural Science Unit, Indian Statistical Institute,
203, B. T. Road, Calcutta-700 035, India.


Keywords : Sundarbans, Mangroves, Leaf, Inorganic elements.

  Mangrove vegetation of Sundarbans, West Bengal is dominated by heterogeneous assemblage of sait tolerant trees and shrubs (true mangroves) and a few herbs and twiners (mangrove associates). Sundarbans is the typical and largest formation of such forest -which extends from the eastem shore line of India and Bangladesh.

  The inorganic components of these plants or plant-parts have been analyzed from time to time by different authors, but a little work has been published on the mature leaves of trees of the Sundarbans. The object of the present paper is to record the status of major inorganic elements i.e. N, P, K and Na of the mature leaves of dominant plants of the Sundarbanns, Moreover, it is of interest to know the sodium-potassium balance of the plants, because the potassium nutrition of a plant and sodium status of the soil is significandy linked together (Raniamo.orthy and Valayutham 1978).

  Twenty six species were collected from different islands of eastem part of the Sundarbans of Indian territory of which 20 species are "true mangroves" and the remaining species are "mangrove-associates" (Tomlinson 1986). Kjeldal-digestion procedure was followed for estimation of nitrogen (Jackson 1973). Tri-acid digest method was used for estimating phosphorus, potasssium and sodium, where sodium and potassium were estimated flamephotometrically and phosphorus colorimetrically (Volhard 1956). Mean of three results of each estimation is given in Table 1. CD values were computed to fmd -out the significant difference of the observed data among the plants at 5% probability level.

  Nitrogen content of the mature leaves varies within a wide range and it is important to consider from the view point of the total protein content of the leaves. The highest N concentration occurs in the mangrove associates e.g. Derris trifoliata (2.756%), Allamanda cathartica (2.525%) and Heliotropium curassavicum (2.181%) etc. Among the true mangroves Nypa fruticans (2.095%), Avicennia marina (2.006%), A. oeinalis (1.879%) and Sonneratia apetala (1. 802%) have high ainount of N. The poor N content occurs in Heritiera fomes (0.992%), H. littoralis (1.012%) and Ceriops tagal (1.067%).

  Among the true mangroves comparatively high amount of P occurs in Heritiera littoralis and H.fomes (0.252 and 0.234%, respectively) and lowest in Bruguiera gymnorrhiza (0.063%) and Aegiceras corniculatum (9.076%). The mangrove associates also show relatively high amount of P such as Allamanda cathertica (0.288%), Heliotropium curassavicum (0.341 %) and Sesuvium portulacastrum (0.246%).

  The two monocot mangroves Nypa fruticans and Phoenix paludosa show highest K concentration (2.322 and 2.600%, respectively). In dicotyledonous mangroves Heritiera littoralis (2.152%) and H. fomes (1.943 %) have the highest and in the two Rhizophoraceae members, Ceriops decandra (0.823%) and Rhizophora mucronata (0.903%) have the lowest amount of K.

Table 1. Amount of N, P, K and Na in the leaf sample (g/100 g dry wt.).

N° Name of the Taxa Family N P K Na
Monocotyledons
1. Nypa fruticans Arecaceae 2.095 0.229 2.322 1.071
2. Phoenix paludosa Arecaceae 1.645 10.107 2.600 1.004
3. Porterasia coarctata* Poaceae 1.643 0.152 1.399 2.440
Dicotyledons
4. Acanthus ilicifolus Acanthaceae 1.313 0.127 1.519 3.124
5. Aegilalitis rotundifolia Plumbaginaceae 1.389 0.110 1.071 1.125
6. Aegiceras corniculatum Myrsinaceae 1.085 0.076 1.503 1.201
7. Allamanda cathartica* Apocynaceae 2.525 0.288 1.240 2.952
8. Avicennia alba Avicenniaceae 1.673 0.124 1.221 1.850
9. A. marina Avicenniaceae 2.006 0.109 1.448 2.130
10. A.officinalis Avicenniaceae 1.879 0.081 1.571 2.001
11. Bruguiera gymmnorrhiza Rhizoraceae 1.182 0.063 1.051 2.249
12. B. parviflora Rhizoraceae 1.679 0.104 1.223 2.939
13. Ceriops decandra Rhizoraceae 1.120 0.063 0.823 2.849
14. C. tagal Rhizoraceae 1.067 0.101 1.448 1.652
15. Clerodendrum incerne* Verbenaceae 1.079 0.100 1.622 3.324
16. Derris trifoliata* Leguminosae 2.756 0.211 1.373 0.823
17. Excoecaria agallocha Euphorbiacae 1.390 0.163 1.459 1.052
18. Heliotropium curassavicum* Boraginaceae 2.181 0.341 1.369 3.056
19. Heritiera Sterculiaceae 0.992 0.234 2.152 0.244
20. H. littoralis Sterculiaceae 1.012 0.252 1.943 0.494
21. Rhizophora mucronata Rhizophoracea 1.012 0.252 1.943 0.494
22. Sesuvium portulacastrum* Aizoaceae 1.771 0.246 1.609 3.174
23. Sonneratia apetala Sonneratiaceae 1.802 0.163 1.072 2.579
24. Sueada maritima* Chenopodiaceae 1.611 0.081 1.902 3.125
25. Xylocarpus granatum Meliaceae 1.239 0.104 1.404 2.953
26. X. mekongensis Meliaceae 1.319 0.240 1.073 2.302
CD ( P=0.05 )
*Mangrove associates.

  Sodium helps to maintain a sufficiently high osmotic pressure to prevent desiccation of cells bathed by a solution of high osmotic pressure(Guillard 1962). Porteratia coarctata has high Na concentration. A trend of accumulation of relatively high amount of Na is noticed in several members of Rhizophoraceae and Meliaceae. In true mangroves the highest amount of Na occurs in Acanthus ilicifolius (3.124%) and the lowest in Heritierafomes (0.244%) and H. littoralis (0.494%). Most of the mangrove associates such as Allamanda cathartica (2.952%), Clerodendrum incerine (3.334%), Heliotropium curassavicum (3.056%), Sesuvium portulacastrum (3.174%) and Sueada maritima (3.125 %) have remarkable concentration of Na.

  The results reveal that most of the mangrove associates possess high amount of N in their leaves, CD (P = 0.05) indicates the statistical homogeneity among different species in respect of phosphorus concentration with a few exception. An interesting relationship is observed between K and Na status in most of the plants. The amount of K is high where Na is low or vice versa. For example, in Heritiera and Phoenix the K values are high while Na values are low, and in Rhizophora mucronata, the K content is low but Na is high. This type of observation was also reported by Rains and Epstein (1 967), in Aegiceras and Avicennia. The present study supports the idea that Na can substituts K to some extent at least in halophytes. Sodium maintains the osmotic pressure within the cell sap, and prevents desiccation of cells bathed by a high saline condition. Presence of very low amount of Na in Heritiera and to some extent in Nypa indicates their inability to withstand the salinity of the substratum of western Sundarbans.

References
Guillard, R.R.L. 1962. In: Physiology and Biochimistry of algae (Ed) R. A. Lewin. Academy Press, New York, London. pp. 529-540.
Jackson, M. L. 1973. Soil chemical analysis. Prentice Hall of india Pvt. Ltd., New Delhi.

Ramamoorthy, B. and M. Velayutham. 1978. Nitrogen, phosphorus and potassium in soil chemistry: Form and availability. In : Soil fertility : Theory and practice (Ed. J. S. Kanwar). Indian Council of Agricultural Research, New Delhi. pp. 156-201.

Rains,D.W.and E.Epstein. 1967.Preferential absorption of potassium by leaf tissue of the mangrove Avicennia marina: An aspect of halophytic competence in coping with salt. Aust. J. Biol. Sci. 20: 847-857.
Tomlinson, P. B. 1986. The Botany of Mangroves. Cambridge Univ. Press, New York. pp. 413.

Volhard, A. 1956. In: Modem methods of Plant analysis, (Eds. Peach, K. and M. V. Tracy), Springer - Verlag, Berlin. pp. 487.

(Manuscript received on 21 November, 1995; revised on 5 May, 1996)
Published on mangroves web site (Webmaster) on June 2000 under the author's permission,
© SAUREN DAS AND MONORANJAN GHOSE

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