5 Anatomy of Indian Bamboos P.K. Pande 1. Introduction India has a rich diversity of bamboos. They belong to family Poaceae; subfamily: Bambusoideae which comprises both lignified and herbaceous bamboos or bamboo allies. Different authors reported different numbers of bamboo species from around the world. Varmah and Bahadur (1980) reported nearly 1,000 species; Ohrnberger and Goerrings (1985) estimated 130-160 species under 25 genera for herbaceous bamboos, whereas woody bamboos are 880-980 species under 85 genera; Biswas (1988) reported 1,200 species under 70 genera and Clyton and Reinvoize (1986) reported 840 species under 49 genera. In India, 115 species were from Indian subcontinent whereas 63 species under 13 genera from present day India (Gamble (1896). Other reports are: Tiwari (1992) reported 125 species under 23 genera; 128 species under 18 genera (Seethalaksmi and Kumar, 1998); 145 species under 23 genera and 115 species under 20 genera were reported by Naithani (2008). The North- Eastern region of India has more or less 50 per cent of total bamboo species occurring in India (Chauhan and Pal, 2002). Bamboos have been recognized as a special group since the beginning of human civilization because of their diverse uses which include construction, handicrafts, edible shoots, furniture and pulp and paper. Now a days, they are also used as substitute of canes, plywood and particle board and as soil stabilizer. Despite the diverse uses of bamboos, often specific bamboos are used for specific purposes for which their exact identity must be ensured. Identification of bamboos is difficult based on floral morphology because bamboos flower sporadically, annually, periodically with intervals of 20-120 years or mostly just once in lifetime. Therefore, information on both anatomical and morphological features are important for their identification. Structure of epidermis of bamboos is important 110 P.K. Pande among the anatomical features. It is considered conservative feature which is least influenced by environment making it an important feature for identification. Other important features in this connection are long cells, short cells, cork cells and silica cells. Silica cells are characterised by silica bodies, which regardless of shape of the cells containing them, assume characteristic shape in different species, and walls of cork cells also contain silica. Besides, stomata and their exodermal appendages are also significant in this direction. Collectively all these features exhibit characteristic patterns for specific species. The information on bamboo leaf was accounted (Metcalfe, 1960; Bisen, 1987) while on culm epidermis reported by many workers (Ghosh and Negi, 1960; Pattanath and Ramesh Rao, 1969; Bisen, 1987; Bisen et al., 1989, 1991; Agrawal and Chauhan, 1990, 1991, 1993; Chauhan et al., 1992, 1993, 1996; Chauhan and Agrawal, 1995; Chauhan and Rao, 1998; Chauhan and Pal, 2002). Besides, anatomy of culm and leaf epidermis is important for structure related studies and identification while fibre and vessel dimensions are important for commercial utilization of bamboos. 2. Anatomy of Bamboo Culm 2.1.Gross Anatomy The internodes and nodes are parts of bamboo culm. The cells are axially oriented at internodes and they have the transverse interconnections at nodes. Intensive branching of vessels occurs within the nodes. Two epidermal cell layers form outer part of culm, of which the inner layer is thicker and highly lignified. Culm internode of bamboo is determined by the shape, size, arrangement and number of the vascular bundles. The vascular bundles are large in size at central portion with low frequency, and smaller with higher frequency in peripheral zone. In general, the bamboo culm is composed of about 50 per cent parenchyma, 40 per cent fibre, and 10 per cent conducting tissues with some variation from species to species. 2.2.Vascular Bundles The vascular bundle in culm of bamboos consists of xylem with one or two smaller protoxylem elements and two large metaxylem vessels accumulating wall material, which are connected with each other by membranes in the early stages of development. During extension growth of the cell, they are disrupted. The walls of metaxylem vessels of bamboo are characterized by a middle lamella and a primary wall with a well developed zonation of the secondary wall into S1 and S2. Anatomy of Indian Bamboos 111 Both the metaxylem vessels and the phloem tissue are surrounded by sclerenchyma sheaths. They differ considerably in size, shape and location according to their position in the culm and the bamboo species (Grosser and Liese, 1971, 1973; Wu and Wang, 1976; Jiang and Li, 1982). There are following five major types of vascular bundles (Liese, 1985): Type I: Consisting of one central vascular strand, supporting tissue only as sclerenchyma sheaths; Type II: Consisting of one central vascular strand, supporting tissue only as sclerenchyma sheaths, sheath at the intercellular space (protoxylem) strikingly larger than the other three; Type III: Consisting of two parts, the central vascular strand with sclerenchyma sheaths and one isolated fibre bundles; Type IV: Consisting of three parts, the central vascular strand with small sclerenchyma sheaths and two isolated fibre bundles outside and inside the central strand; Type V: A semi-open type representing a further link in the evolution tendency. The vascular bundle types and their distribution within the culm correlate with the taxonomic classification system of Holttum (1956) based on the ovary structure. Type I alone: Arundinaria, Phyllostachys, Fargeria, Sinarundinaria Type II alone: Cephalostachyum, Pleioblastus Type II and III: Oxytenanthera, Melocanna Type III alone: Schizostachyum Type III and IV: Bambusa, Dendrocalamus, Gigantochloa, Sinoclamus Leptomorph genera have only the vascular bundle type I, whereas Pachymorph genera possess types II, III and IV. Size and shape of the vascular bundles vary across an internode but also with the height of a culm (Liese, 1985). 3. Variation in fibre Dimensions, Specific Gravity and Anatomical Pulping Properties The fibre morphology of 10 economically important bamboo species, viz., Dendrocalamus giganteus, D. hamiltonii, D. longispathus, D. strictus, Melocanna baccifera, Bambusa bambos, B. polymorpha, B. tulda, Ochlandra travancorica and Arundinaria racemosa has been described by Pande (2009). Variations among the species were significant for the fibre dimensions. It showed that material from one bamboo species of the same site carry similar fibre properties while they are different for different bamboo species. 112 P.K. Pande Range and mean±SD for fibre dimensions and length/diameter ratio are given in Table 3.1. The order of importance as per the mean fibre length (µm) was O. travancorica (4,320) followed by D. hamiltonii (3,200), B. polymorpha (3,150), D. strictus (3,190), B. tulda (3,020), M. baccifera (2,750), B. bambos (2,720), D. giganteus (2,650) and A. racemosa (1,003). The average fibre diameter ranged from 12 to 16 µm. The range for other grasses and reeds for average fibre length and diameter was 780 to 4,580 µm and 12 to 31 µm, respectively. The average fibre length for agriculture residue was 700 to 1,700 µm and for fibre diameter was 13 to 55 µm. Comparison of fibre dimensions with other pulp making raw material is given in Table 3.2. Bamboo material showed higher fibre length than that of the other material. The length is comparable with agriculture residue. However, fibre diameter was higher in hard and soft woods. Further, variations in stem anatomical characters, specific gravity and anatomical pulping properties of five bamboo species, viz., B. balcooa, B. nutans B. pallida, B. tulda and D. hamiltonii were studied by Naithani and Pande (2010). Table 3.1. Fibre length, fibre diameter and length/diameter (L/D) ratio of different bamboo species Species Fibre length (µm) Fibre diameter (µm) L/D±SD Range Mean±SD Range Mean±SD Arundinaria racemosa 330-2,500 1,003±200 8-40 15±1.5 66.15±17.21 Bambusa bambos 700-4,200 2,720±203 6-18 12.5±0.5 218.26±24.78 B. polymorpha 1,000-5,600 3,150±50 7-29 14±0.6 220.08±11.75 B. tulda 1,010-5,020 3,020±189 6-32 14±0.1 215.68±9.17 Dendrocalamus giganteus 1,450-4,700 2,650±150 6-30 13±0.6 210.34±20.96 D. hamiltonii 1,550-6,900 3,200±92 7-22 13±1.5 241.95±26.12 D. longispathus 1,000-5,500 3,510±101 6-28 14±1.2 246.31±26.87 D. strictus 1,100-5,600 3,190±543 7-33 14±0.6 223.08±41.91 Melocanna baccifera 1,150-4,800 2,750±150 8-38 15±1.6 185.27±11.39 Ochlandra travancorica 1,200-9,000 4,320±257 7-43 16±0.6 264.58±20.09 Source: Pande, 2009. Table 3.2. Comparison of fibre dimensions of different raw material Character Hard wood Soft wood Grasses Agriculture residue Bamboo Fibre length 710-1,400 390-3,640 780-4,580 700-1,700 1,003-4,320 Fibre diameter 9.6-62 27-52 12 -31 13-55 12-16 Source: Singh et al., 1991. Anatomy of Indian Bamboos 113 4. Inter-Species Variation Table 4.1. shows the minimum, maximum and average values of fibre length, wall thickness and specific gravity of different species of bamboos. The highest average value of fibre length and wall thickness was in D. hamiltonii followed by B. balcooa, B. nutans, B. pallida, B. tulda and M. baccifera. Clone C1 (B. balcooa), C6 (D. hamiltonii), C8 (B. nutans) and C7 (B. tulda) showed invariably higher fibre dimensions and specific gravity. Though some of these clones showed higher values of RR which are not in the permissible range, other properties are within the permissible range for the pulping.