0359-B4
Sas. Biswas and Alpana 1
In India farmers grow poplar as intermix agricultural crops without any appreciable reduction in yield. A large number of exotic poplars have been introduced in India during the past over three decades. There is growing concern towards the production, utilization and conservation of poplars world over. Although both indigenous and exotic species of Populus taxonomically have been documented in the regional flora of different parts of the world but the intra/infraspecific variability of morphological, phenological and phytogeographical significance of the species remain un/understudied. Taxonomic studies within the species level are important wherever the consistent variation of taxonomic significance form the basis for the selection of clones/provenance.
The present studies reveal the information about the morphological features of exotic clones growing in India. During the course of introduction, transplantation and distribution of the clonal materials, the basic identity of the propagating and harvested germplasm is lost by and large as a result of mixing up subconsciously by the non-technical hands. Therefore, authenticity of the plant for the desired growth and yield becomes doubtful. Sometimes the losses are heavy when the estimated yield is not obtained, just for want of authentic parameters of morphological features and ready reckoned. It deserves a mention here that the clonal taxa of poplar growing in India do not pass through reproductive phase. Therefore, it becomes difficult to determine the various clones based upon sexual characters. Therefore, studies based on morphological and phenological characters such as habit, form, shape, surface, color of stem, color of the bark, leaf (measurement), phyllotaxy, leaf stalk, petiole, number of glands, shape of gland, leaf base, kinds of leaf, leaf texture and winter buds (position, shape, size, color, occurrence, exudation and orientation of various morphological feature of taxonomic significance related to 200 clones were carried out. Research need and priorities have been outlined in the paper.
Poplars by virtue of their fast growth offer a great potential for meeting the growing demands of wood-based industries and farmers. As the poplars remain leafless during winter they are suitable under different agro-forestry practices. Poplar cultivation is attractive because it can produce wood on a short duration. It suits agroforestry in India on accounts of its deciduous nature, which permits enough sunlight for cultivation of winter crops. Farmers grow poplar as intermix agricultural crops without any appreciable reduction in yield. The important immediate benefits of poplar trees to farmers are in the form of fuel wood obtained through pruning. Their wood is in much demand for pulp and paper, plywood, matchwood, packing cases and light constructional timber all over the world. A large-scale plantation using suitable fast growing species and clones that can be harvested in short rotations are being raised. The choice of this species lies in its faster growth, responding well to intensive cultural treatments and easy propagation.
The genus Populus (Salicaceae) is represented world over by approximately 35 species distributed throughout the forests of temperate regions of Northern Hemisphere. It is divided into 5 sections viz. Turanga, Lecue, Aigeiros, Tacamahaca and Leucoides. There are six species of poplars indigenous to India namely Populus ciliata Wall. ex Royle, P. euphratica Oliver., P. laurifolia Ledeb., P. alba Linn, P. gamblei Dode, and P. jacquemontiana var. glauca Haines. A large number of exotic poplars have been introduced in India. Introduction of exotic poplars is of significance to India for its congenial adaptability to the vast range of climate and site conditions. Poplars are widely cultivated on the farmlands, roadsides, riverbanks and canals. It is also used as wind breaks for the protection of agriculture and food crops.
There is growing concern towards the production, utilization and conservation of poplars world over. Although both indigenous and exotic species of Populus taxonomically have been documented in the regional flora of different parts of the world but the intra/infraspecific variability of morphological, phenological and phytogeographical significance of the species remain un/understudied. Natural variation is a renewable resource and occurs as a result of evolution. The variations occurring in natural and introduced populations of Populus are most important genetic resource for selection of suitable clones for the judicious use. Taxonomic studies within the species level are important wherever the consistent variation of taxonomic significance form the basis for the selection of clones/provenance. During the course of introduction, transplantation and distribution of the clonal materials, the basic identity of the propagating and harvested germplasm is by and large lost as a result of mixing up subconsciously. Therefore, authenticity of the plant for the desired growth and yield becomes doubtful. Sometimes the losses are heavy when the estimated yield is not obtained, just for want of authentic parameters of morphological features.
There are 330 clones included in the International Register of Populus cultivars under one of the ambitious programs of the subcommittee for Nomenclature and Registration of the International Poplar Commission. This relates to the significant aspects of present studies. The International Rule of Nomenclature for cultivated plants, a body under International Code of Botanical Nomenclature (ICBN) the designation of cultivated variety must be assigned at three levels i.e. genus, species and cultivar. In case of cultivated poplars, the cultivars are generally clones. Cultivar is a contracted word for cultivated variety the conventional sign of abbreviation being - accorded to the OECD (Overseas European Community Development) Scheme for forest reproductive material. As the official registration body, the International Poplar Commission checks the name whether it was not previously given to another cultivated variety with a view to avoid any possibility of confusion. The present studies have several taxa and clonal materials by names/ letters such as `WSL', `G', ` D' `I', and by the digits such as `2', `82- 6- 5', `111234' and `S7C3' bearing no sign of origin of taxa and remained as the taxonomists' nightmare. Present studies find that the experimental nurseries are generally making use of an alphanumerical code and/or the color paint girdling of the clonal materials for the short time convenience. But it is obvious that the risk of mistakes is very great, especially when some new unregistered clones are exchanged without complete information on their code of identification.
The main purpose of the present studies carried out during 1990 - 2002 was to ascertain the taxonomic position of different taxa of genus Populus both indigenous and exotic introduced in India through systematic studies with out recourse to reproductive characters keeping under consideration the main objectives such as to ascertain the correct identity and nomenclature update of various taxa and clones of poplars growing in India, and to study the taxonomic characters of Populus species and their clones for systematic accounts and ready reference.
Field survey and collection of infra-specific indigenous and exotic taxa in poplar growing areas in plains and hills of India occurring in various orchards, germplasm banks and nurseries for taxonomic characterization. Emphasis was laid on economically useful clones being introduced by the growers of the states of Punjab, Haryana, Uttaranchal and Uttar Pradesh northern region of the country. The collected materials were preserved as herbarium specimens for incorporation in the Herbarium of Forest Research Institute, Dehra Dun for future reference and authentication of germplasm.
Field observation was made on morphological and phenological variability among the taxa. Characteristic features such as bark, leaf, reproductive parts and phenological aspects particularly of different clones/provenance were studied for systematic accounts. Orientations of vegetative and reproductive buds were studied in terms of taxonomic approach for the identification of different taxa. For correlating growth at the time of maturity of different clones with respect to long and dwarf shoots of useful clones taxonomic observation was made. The field characters were gathered on pre-designed database format.
An enumerative checklist on the infrageneric and infra-specific taxa was compiled. Nomenclature of doubtful and complex taxa was updated for taxonomic studies.
From taxonomic point of view on 360 clonal materials, many of them named commonly and as admixture by different names, number and painted in different colors growing in various locations were gathered and studied. The age of the clonal stands considered for taxonomic studies ranged from 1-3 years and those old stands growing without any indication of time of introduction and age. The observation of taxonomic significance was from the diagnostic features of consistent nature. It was found that morphologically and phenologically the taxa fall under much lesser taxonomic entity, that is 200 in number of exotic clones for systematic accounts.
Statistical synopsis on the species and clones found in India:
S.N. |
Species / Clones |
No. of Taxa |
S.N. |
Species / Clones |
No. of Taxa |
1. |
Indigenous species |
6 |
3. |
Clones of Populus deltoides |
196 |
2. |
Exotic species |
4 |
4. |
Clones of Populus x euramericana |
4 |
Analysis of taxonomic characters based on matured twig reveals that there are 32 groups of taxonomic entities (clonal admixture and individual clones). The clones with round twig and stiff nature of stem of one year comprised of as many as 28 clones where those with round twig and nature not stiff have 47 clones. The clones with ribbed twig and stiff stem of 1 year old comprised of as many as 27 clones while the clones with ribbed twig and non-stiff nature are with 98 clones. The colors of the twig what make the clonal material identifiable in the field range from green to brown with various shades. Conclusively 200 clones have been classified into 32 groups including 8 distinct taxonomic entities. Taxonomic characters based on petiole depict that there are 6 groups of taxonomic entities. The clones are differentiated or separated on the basis of colors in the field range from green to variously brown and distinctly yellow. The petiole with green color comprised 78 clones, variously red-13 clones and variously yellow 109 clones. Conclusively 200 clones are classified into 6 groups including 1 distinct taxonomic entities. Observation made on leaf glands shows that there are 19 groups of taxonomic entities. The clones with green glands (elongated, up to 2 and between 2-4) comprised 50 clones whereas clones with red glands (round not round, up to 2 and between 2-4) includes 82 clones and yellow glands (elongated/ not elongated, up to 2 and between 2-4) comprised 68 clones. 200 clones are ultimately classified into 19 groups including 9 distinct taxonomic entities. Separation of taxonomic characters is based upon leaf shows that there are 65 groups of taxonomic entities (clonal admixture and individual clones). The characters of leaf with ovate shape and cordate base have 53 clones whereas the ovate with sub cordate base have 32 clones only. Leaf broadly ovate with cordate base comprised 48 clones while narrowly ovate with cordate base. The characters of ovate leaf with cordate base have 53 clones, sub cordate have 21 clones and truncate base have 11 whereas leaf broadly ovate with cordate base comprised 39 clones, truncate base have 9 clones. The leaves with narrowly ovate and cordate base have 7 clones, sub cordate base have 2 and truncate base having 4 clones. The leaf of deltoid characteristic with base cordate have 16 clones, subcordate have 18 clones whereas leaf with truncate base comprised of 19 clones. The colors of midrib and the leaf contribute to the characterization of clonal material. The colors (green, yellow and red) of mid rib and the leaf margin make the clonal material identifiable in the field. It is found that 200 clones are classified into 65 groups including 35 distinct taxonomic entities. Taxonomic characters based on trident of one year old node of stem reveals that there are 94 groups of taxonomic entities. The clones with trident present, arm conspicuously ribbed comprised of 127 clones while those with arms of trident inconspicuously ribbed have 48 clones. The clones without trident and fainted comprised of 36 clones.The variety of colors makes clonal material identifiable in the field with green to brown. 200 clones studied are subsequently classified into 94 groups including 47 distinct taxonomic entities.
Studies based on winter bud, a most important feature of taxonomic importance, shows that there are 97 groups of taxonomic entities (clonal admixture and individual clones). The clones with long terminal (1.0-1.5 cm) orientation and broadly ovoid shape comprised of as many as 31 clones whereas the clones with narrowly conical shape have 69 clones. The clones with short terminal (0.5-1.0 mm) orientation, broadly ovoid shape comprised of 44 clones while the clones with narrowly conical shape have 51 clones. The variation of color (brown, green, orange, brown), position and leaf scar of bud makes the clonal material diagnostically recognizable in the field. Thus the 200 clones fall under 97 groups including 58 distinct taxonomic entities.
Significant findings of the work elucidate on the development of a comprehensive analytical key based on morphological characters for identification of all the 200 clonal taxa and iconographic details of the features on each of the 200 taxa with systematic details leading to the identity of the clonal material needed for the convenient referencing.
Research need and priorities of the work carried out are as follows (i.) the works on larger area with the taxa of Populus under plantation/ cultivation or on any other landscapes, nomenclature confusion, duplication and ambiguity among the clonal admixture. (ii) Preparation of taxonomic treatise for ready reference on the morphological characters of various species and clones of poplar growing in developing and developed countries where poplars have been adjudged as the species of intensive forestry research and development, (iii) Establishment of Germplasm Bank of regional to international levels depicting various clones/intra and infra specific variability from the indigenous source to the well-introduced areas, (iv) Certification for the registration of clonal materials in advance to avoid duplication or materials with superfluous identity or nomenclature. This would help in characterizing the taxa for specific use. (v) Preparation of an electronic compendium such as CD, CD-ROM and Website based on present details for the use of technical and non-technical hands dealing on various aspects of this forestry important tree and genetic resource, and (vi) Authentication of material for integrated studies using recent trends and related subjects for correlation of taxonomic findings with genetic diversity measurement.
Alpana and Biswas, Sas. (1999). Taxonomic evaluation of some important clones of poplar through studies on their winter buds. Indian J.Forestry, 22: 391-393.
Alpana and Biswas Sas. (2001). Contribution to the taxonomy of Populus Linn. and its some useful clones growing in India. Proceed. 88 th Session of Indian Science Congress Association, Section of Botany. New Delhi: 6.
Biswas, Sas., Chandra, V. and Chandra, S. (1990). On the distribution and conservation of five spectacular and endangered ligneous species of Sikkim Himalaya. Van Vigyan 28(3): 106-116.
F.A.O. (1958). Poplar in forestry and land use. (FAO Forestry and Forest Product studies) 12: 1-55. Rome.
Tewari, D.N. (1993): Poplar , pp 321. Surya Publications, Dehra Dun - 248001, Uttaranchal (India).
1 Botany Division, Forest Research Institute
Dehradun-248006, Uttaranchal, India
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