Plant fibres.........................pptx

Plant fibres

1. PLANT FIBERS Submitted to,
Dr. Chandini V. K
Asst. Professor
ST. Teresa’s College, Ekm Submitted by, A.T Milin Sera Roll no : 1 1st M.sc. Botany ST. Teresa's College, Ekm

2. INTRODUCTION TO FIBRES Sclerenchyma is a tissue composed of cells with thickened secondary cell walls .
Their cell walls may be lignified or not and contain pits .
Their principal function is support and sometimes protection .
Sclerenchyma cells may differ in shape, structure, origin and development.
Generally, sclerenchyma is divided into fibres and sclereids . 1

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4. FIBRES Fibres are elongated cells often with pointed ends , thick secondary wall and reduced pits .
Certain other types of fibres possess blunt or even branched ends .
As the fibres get old, the protoplasmic contents become multinucleate and finally disappear.
But in certain cases, fibres retain protoplast even upto the permanent stage.
Some fibre walls contain lignin while certain fibres like those occurring in flux ( Linum usitatissimum ) the wall is made up of pure cellulose . 3

5. OCCURRENCE OF FIBRES Fibres occur in different parts of the plant body. They may occur singly as idioblasts (e.g. in the leaflets of Cycas). But more usually they form bands or a network or an uninterrupted hollow cylinder . They are most commonly found among the vascular tissues but they are also well developed in the ground tissues . Gymnosperms usually have no fibers in the primary phloem, but many have them in the secondary phloem . In Gramineae the fibers form a system having the shape of a ribbed hollow cylinder, with the ribs connected to the epidermis. 4

6. In Zea , Saccharum , Sorghum the vascular bundles, particularly the peripheral ones, have prominent sheaths of fibers . Fibers may be prominent in the leaves of monocotyledons. They form sheaths enclosing the vascular bundles, or strands extending between the epidermis and the vascular bundles.
In stems of dicotyledons, fibers frequently occur in the outermost part of the primary phloem .
Others develop fibers in the secondary phloem ( Nicotiana , Ulmus ). Monocot stem 5

7. Some dicotyledons have complete cylinders of fibers. They are located to the inside of the inner- most layer of the cortex ( Cucurbita ). A highly characteristic position for fibers in the angiosperms is in the primary and the secondary xylem . Roots may have fibers in the primary and in the secondary body. Dicot 6

8. CLASSIFICATION OF FIBRES According to their position in the plant body, fibres are classified into two basic types xylary and extraxylary fibres . 1.) Xylary fibres : constitute an integral part of the xylem and they develop from the same meristematic tissues as the other xylem elements. These fibres are of varied shape in spite of their common origin. Two main types of xylary fibres, i.e. libriform fibres and fibre-tracheids, are distinguished on the basis of wall thickness and type and amount of pits. 7

9. Libriform fibres : resemble phloem fibres (liber- inner bark). They are usually longer than the tracheids of the plant in which they occur. These fibres have extremely thick walls and simple pits. Fibre-tracheids : are forms intermediate between tracheids and libriform fibres.
Their walls are of medium thickness-not as thick as those of the libriform fibres but thicker than those of the tracheids.
The pits are bordered but their pit chambers are smaller than those of tracheids. Libriform fibres Fibre tracheids 8

10. Another type of fibre present in the secondary xylem of dicotyledons is the gelatinous or mucilaginous fibre . Mucilaginous fibres : are fibres in which the innermost layer of the secondary wall contains much cellulose and is poor in lignin. This layer, termed the “ G-layer ”, absorbs much water and may swell so as to fill the entire lumen of the fibre. The G-layers were found to be relatively porous and less compact than the adjacent outer layers. Septate fibres : are characterized by the presence of internal septa and, usually, of a living protoplast. 9

11. The internal septa result from mitosis in lignified cells.
The septum does not fuse with the fibre wall but becomes broadened, at the place of contact with it. The tips are running out as pointed ends when viewed in longitudinal section of the fibre. The septum consists of a middle lamella and two primary wall-like layers interrupted by numerous plasmodesmata.
Septate fibres may contain starch and oils and, therefore, are thought to have a storage function.
They may also contain resins and sometimes crystals of calcium oxalate. Septate fibres with radial canal 10

12. There is also some elongated cells that sometimes occur in the secondary xylem. Their secondary walls are equal in thickness to those of the xylem parenchyma and contain living protoplasts.
According to Haberlandt (1918), they were termed by Sanio, substitute fibres (Ersatzfasern).
It appears that these cells should be included among the xylem parenchyma. They should not be confused with the living libriform fibres and fibre-tracheids. 11

13. 2.) Extraxylary fibres : occur elsewhere in the plant other than among the xylem elements. Phloic or phloem fibers : fibers originating in primary or secondary phloem. Cortical fibers : fibers originating in the cortex. Peri - vascular fibers : located on the periphery of vascular cylinder inside the innermost cortical layer but apparently not originating in the phloem. In the stems of many monocotyledons, the extraxylary fibres occur in an uninterrupted hollow cylinder in the ground tissue. 12

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15. In the stems of climbing and certain other dicotyledonous plants ( Cucurbita) , fibres are found on the innermost cortical layer and on the periphery of the central cylinder.
These fibres are not developmentally connected with the phloem, they were termed as pericyclic fibres by many workers.
As a result of ontogenetic studies in stems of some plants ( Nicotiana , Linum, Nerium ) it has been concluded that the so-called pericyclic fibres develop from the procambium and thus represent primary phloem fibres. The extraxylary fibers are sometimes combined into a group termed bast fibers . The bast (to bind) was originally applied to fiber strands obtained from the extracambial region of dicotyledonous stems. 14

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17. ORIGIN OF FIBRES Fibers arise from various meristems. Fibers of the xylem and the phloem are derived from procambium or cambium . In the cambium, the fibers arise from the fusiform initials . Extraxylary fibers other than those of the phloem arise from the ground meristem. In some Gramineae and Cyperaceae, fibers originate in the protoderm and become elements of the epidermis. In plants having fibrous bundle sheaths, part of the fibers may be derived from the procambium and part from the ground meristem . The fibrous bundles of monocotyledons appear to be connected with vascular bundles and they are considered as originating from the procambium. 16

18. STRUCTURE OF FIBRES (I) Extraxylary Fibers : A long spindle-like shape is considered typical of extraxylary fibers (fibers in general). These elements may vary in length, and their ends are sometimes blunt, rather than tapering, and may be branched. Generally, primary extraxylary fibers are longer than the secondary.
The cell walls of the extraxylary fibers are frequently very thick. The pits are simple or slightly bordered. Some extraxylary fibers have lignified walls, others non-lignified. 17

19. The flax fiber ( Linum usitatissimum ) is typically not lignified, its secondary wall consists of almost pure cellulose. Concentric lamellations may be observed in extraxylary fibers with or without treatment with swelling reagents.
This lamellation appears to result from an alternation of cellulosic and noncellulosic layers.
In cotton fiber, the lamellation is a reflection of varying densities of the cellulosic matrix in the successive lamellae. 18

20. (II) Xylem Fibers : Wood fibers typically have lignified secondary walls. They vary in size, shape, thickness of wall, and type and abundance of pitting. With reference to the possible evolution of the xylem fibers, different categories of these fibres are understood. Phylogenetically, these fibers are believed to be derived from an imperforate xylem cell combining the functions of water conduction and support, that is, a tracheid . 19

21. A good indication that fibers and tracheids are phylogenetically related is the occurrence of almost imperceptible gradations between these two cell types in certain angiosperms such as the oak. The gradations suggest the following principal changes during the evolution of the fiber from a tracheid: (i) increase in wall thickness, (ii) decrease in length, and (iii) reduction in the size of bordered pits. In the extreme condition the pit appears simple or nearly so. Wall thickness and the nature of pitting are used to differentiate between the two main categories of wood fibers, fiber-tracheids and libriform fibers.
Fiber-tracheids are cells with pits whose borders are reduced as compared with those in the tracheids. 20

22. Finally the cells with simple pits are classified as libriform fibers.
Commonly, the thickness of wall increases in the sequence of tracheid, fiber-tracheid, libriform fiber. The increase in wall thickness results in an increase in the length of the pit canal.
In the fiber-tracheid these canals lead into small but evident pit chambers. In them the inner apertures are lenticular to slit-like and usually extended beyond the outlines of the border. The libriform fibers also have long slit-like canals, but their pit chambers are much reduced or absent. The inner apertures of the pit-pairs in the fiber-tracheids and libriform fibers are often crossed with each other. 21

23. The tracheids are usually shorter, the fibers longer, with the libriform fibers attaining the greatest length. The fibers become longer than the associated tracheids because they undergo a more extensive apical elongation during tissue differentiation.
Fiber-tracheids and libriform fibers may both be septate. The septa are true walls, but they are formed after the deposition of the secondary layers on the longitudinal walls of the element. 22

24. Parts of the secondary wall of fiber-tracheids and libriform fibers may have a great capacity for absorption of water. In the presence of water such walls swell. Upon drying, these walls shrink again. Fibers possessing hygroscopic walls are sometimes termed mucilaginous or gelatinous . The gelatinous wall layers do not contain excessive amounts of pectinaceous, gummy, or mucilaginous substances. They show a peculiar physical condition of the cellulose which possibly is responsible for their gelatinous nature. Many woods contain gelatinous fibers. Oak ( Quercus ) and black locust ( Robinia ) are noteworthy examples. 23

25. EVOLUTION OF XYLARY FIBRES From the evolutionary point of view, xylary fibres have developed from tracheids. This assumption is supported by the fact that many transitional forms between these two types of elements are found in some angiosperms, e.g.:- Quercus spp . It is assumed that the following changes have taken place during the course of the evolution of fibres from tracheids : The wall has become thickened. The number of pits and the size of the pit chamber has been reduced leading to the eventual disappearance of the bordered pit. The cells have become shortened. 24

26. This assumed shortening of the fibres refers to the shortening of the initials of the fibres in the cambium and not to the mature fibres.
In the mature tissues of one plant, the libriform fibres are usually longer than the tracheids.
This increased length is secondary and is the result of the additional growth of the ends of the fibres. 25

27. FORM AND LENGTH OF FIBRES Fibres are usually very long and narrow cells with tapered, and sometimes branched, ends. The length of fibres varies very greatly and generally extraxylary fibres are longer than xylary fibres. In Cannabis sativa (hemp) the fibres are 0.5-5.5 cm long. In Linum usitatissimum (flax), fibres are 0.8 to 6.9 cm long. In Boehmeria nivea (ramie) the fibres may reach a length of 55 cm. These ramie fibres are among the longest cells in the higher plants. 26

28. DEVELOPMENT OF FIBRES Ontogenetically fibres develop from different meristems, such as the procambium , cambium , ground meristem and even from the protoderm . Fibres may also develop from parenchyma cells, e.g. in the protophloem of many dicotyledons. The fibres formed by the cambium develop from fusiform initials and elongate only little or not at all during their maturation.
Fibres that arise from short initials, as in Linum (flax) and Boehmeria nivea (ramie), must necessarily elongate greatly in the course of their maturation. The elongation is very gradual and may take some months. 27

29. This gradual elongation of primary phloem fibres involves a very complicated development of the secondary wall.
While the fibre still grows symplastically, the wall remains thin. Later, when the ends begin to grow by intrusive growth, only the cell walls of the ends remain thin. Secondary wall formation commences from the middle of the fibre in those parts of wall which have ceased to elongate. In Linum and ramie it has been found that this process is gradual. So the new lamellae of the secondary wall are added centripetally in the form of cylinders which are open at both ends. 28

30. At the same time the first-formed lamellae continue to elongate towards the fibre ends which they reach only when the fibre ceases to elongate. According to Kundu and Sen (1960) the upper ends of ramie fibres continue to grow for a longer period than the basal ends.
Sometimes not all the lamellae reach the actual fibre end. In some fibres, chambers may be formed in the terminal portions by the ingrowth, towards the cell lumen, of these lamellae. The lamellae of the primary phloem fibres, or at least of the immature fibres, are often not strongly attached to one another. 29

31. In short fibres, such as those found in Agave , Sansevieria , and Musa textilis , all portions of the cell wall grow at the same rate. Differences exist in the manner of growth of the fibres in the primary body and of those in the secondary body.
The initials of the primary fibres appear early, before the organ in which they occur has elongated. So they may grow in length symplastically together with the neighboring cells which continue to divide.
The symplastic growth is augmented by intrusive and gliding growth of the ends which thus penetrate between the surrounding cells. The initials of the secondary fibres develop in organs that have ceased to elongate. 30

32. Therefore the growth of secondary fibres can be intrusive only. This is apparently the reason why the primary fibres are usually longer than the secondary fibres of the same plant.
Electron microscopic studies of wood fibres have shown that during secondary wall formation the cytoplasm was in general conspicuously vacuolated, although the vacuolation did not extend to the cell tips. The nucleus was large and the organelles which were generally few in number appeared more crowded near the tips.
The ER frequently appeared to lie parallel to the wall surface.
In the process of wall formation, lamellar apposition of cellulose and vesicular secretion of matrix takes place. 31

33. FIBRE PROTOPLAST During the development of primary phloem fibres of Nicotiana and Linum , the protoplast was multinucleate. The protoplast in developing secondary fibres usually has a single nucleus.
Mature libriform fibres and fibre-tracheids were usually regarded as being dead supporting structures. In mature fibres the presence of a living protoplast and nucleus had been described only in phloem fibres and in septate fibres. According to Bailey (1953), libriform fibres sometimes retain their living contents subsequent to the formation of the thick, lignified secondary wall, thus enabling these cells to assume a storage function in addition to that of support. 32

34. Recently, however, living protoplasts and nuclei have been identified in libriform fibres of many species, and even in fibre-tracheids.
Such living fibres were found to occur in the wood of Tamarix spp., and in many other woody species.
Living protoplasts have also been found in many monocotyledonous fibres.
In fibres with long, narrow lumina the nuclei are usually elongated. During the elongation of the primary phloem fibers in tobacco, the protoplasts become multinucleate as a result of repeated mitotic divisions. Cell plates do not form at the ends of the successive nuclear divisions and the spindle fibers are less persistent than in ordinary division. 33

35. At the final stages in fiber ontogeny, usually after secondary walls have developed, the nuclei appear to fuse or clump. In nearly mature fibers the nuclear material frequently occurs as one large degenerating mass. The bast fibers of Linum also exhibit a multinucleate phase during differentiation. Haberlandt (1914) observed a multinucleate protoplast in the bast fibers of Linum and certain members of the Leguminosae. He suggested that, the presence of several nuclei appears advantageous when the length of many bast-cells and their active growth in length and thickness are taken into account. 34

36. In certain types of fibers, however, mitosis is followed by cytokinesis, resulting in a chambered or septate fibre. In Hypericum androsaemum the fiber-tracheid retains its protoplast after the thick secondary wall has been laid down. Mitosis may then occur in such a cell.
Cell plate formation then occurs in the normal manner. A thin transverse septum is formed across the lumen, intersecting the inner edge of the secondary wall of the “mother cell.” 35

37. STRUCTURE & USE OF COMMERCIAL FIBRES The term fibre, as used in industry, does not generally have the same meaning as that defined by botanists. For instance, the commercial fibres of Linum , Boehmeria , and Corchorus are, in reality, a bundle of fibres. Those from monocotyledonous leaves, such as from Agave , Musa textilis , and others, are usually the vascular bundles with the surrounding sheaths of fibres. From some plants the commercial fibres comprise the vascular system of the root, e.g. Muhlenbergia , or of the entire plant, e.g. Tillandsia . The commercial fibres of Gossypium (cotton) and kapok are the epidermal hairs of the seeds. 36

38. Linum usitatissimum Linen Musa textilis Abaca 37

39. Commercial fibres are divided into two types - hard fibres and soft fibres . Hard fibres : are those which have a lignin content in the walls, and are of a stiff texture. They are obtained from monocotyledons. Soft fibres : may or may not contain lignin, they are flexible and elastic. They are of dicotyledonous origin.
The best- known plants from which hard fibres are produced are different species of Agave , especially sisalana (sisal), Tillandsia usneoides (Spanish moss), Musa textilis (abaca), Fureraea gigantea (Mauritius hemp).
Soft fibres are mainly produced from Linum usitatissimum (flax), Cannabis sativa (hemp), Boehmeria nivea (ramie), Corchorus capsularis (jute), Hibiscus cannabinus (kenaf). 38

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41. The fibres of cotton, which are produced from the indumentum of seeds, represent the most important commercial fibres in use today. Fibres are also classified according to their use : Textile fibres :- which are used in the manufacture of fabrics. Cordage fibres :- used for making cordages. brush fibres :- which are used in the manufacture of brushes and brooms. filling fibres :- such as those used for stuffing upholstery, mattresses and life-belts, caulking (barrels, plumbing), and reinforcing (wall plates, plastics). In the textile industry the principal fibre used is cotton and, in smaller amounts, flax, ramie, and hemp.
For coarser fabrics, such as sacking and bagging, jute is principally used, and cotton, flax, hemp, and a few other hard fibres are used to a lesser extent. 40

42. Cordage Filling fibre Brush fibres 41

43. For the manufacture of twine ; jute, cotton, hemp and, to a lesser extent, flax and several hard fibres are used. Ropes and binder twines are manufactured from hard fibres, such as those of Musa textilis (abaca) and Agave spp . (sisal), and to a small extent from cotton and other soft fibres. Brushes and brooms are made from Agave fibres, fibres from the stems and leaves of the Palmae and the inflorescences of Sorghum vulgare , etc. As filling fibres, the fibres of Ceiba pentandra (kapok), cotton, jute, the fibres of Tillandsia usneoides , several hard fibres, and others are used. Fibres are also used in the paper industry, depending on their physical and chemical properties different types of paper can be made. 42

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45. From a technological point of view, the shape of the fibre cell, its length, and wall structure are of importance in the fibre industry. Special attention is paid to the length of the fibre, the extent to which neighboring fibres overlap, and how they are joined to one another. The orientation of the cellulose units in the wall has an important effect on the physical properties of wood and commercial fibres. Elasticity and heat conductivity increase as the degree of orientation parallel to the length of the fibre increases. Cannabis sativa 44

46. PREPARATION OF COMMERCIAL FIBRES In the preparation of commercial fiber the plants are subjected to a process of partial maceration called retting (technical form of the word rotting).
In this process the plant material is exposed to a decomposing action by bacteria and fungi. These are allowed to act on the plant parts until the tissues surrounding the fibers are so softened that the fibers can be easily freed mechanically. The tissues are left in water for a considerable time while this takes place.
In the early stages of retting only the intercellular material is affected by pectic enzymes. 45

47. Later the primary wall may be also attacked. An effort is made to discontinue the retting process before the fiber strands are macerated into individual cells.
Then the retted stems are dried and passed between rollers, which separates the fibres from the other tissues. Finally they are combed, beaten out and placed in bales. 46

48. COTTON It is one of the most important industrial products. It is the principal textile fiber and also the oldest and the most economical one. Several species like Gossypium herbaceum, G. arboretum, G. barbadense, G. hirsutum yield cotton. Gossypium herbaceum appears to be the most important, as it is the chief species cultivated in Asia.
Its fiber is widely used in fabric industry in India and in other Asian countries. Gossypium 47

49. In a strict anatomical sense, the “fiber” of a cotton seed is not really a fiber at all. Because it is not lignified nor does it occur in the appropriate part of the plant to be called a fiber.
The proper anatomical cell name for the seed “fiber” is a trichome. However, we will adopt the term “fiber” to describe the long hairs on the cotton seed as that is the commonly used term. Each “fiber” is produced by the outgrowth of a single epidermal cell.
The “fibers” are actually hairs that grow out of the seed coats. Processed fibres of Gossypium 48

50. The seed “Fiber” is composed of : (i) cuticle: mixture of cutinous, pectinous substance. (ii) outer cellulose layer: mostly original cell wall.
(iii) layer of secondary deposits: almost all cellulose.
(iv) walls of lumen: spiral structure surrounding the central cavity, most dense part of the “fiber”.
(v) lumen: filled with structure less substance, nitrogenous nature. 49

51. Some epidermal cells make long lint hairs.
Other cells stop growing before they become too long; we call these fuzz hairs.
The fuzz hairs have a bigger diameter and a thinner cell wall. As the boll grows, the “fibers” are maturing within.
In about four months times the boll begins to slit open and the “fibers” are exposed.
Each seed has about 10,000 to 20,000 “fibers”. The boll matures and the “fibers” lose their water and die.
Each “fiber” collapses and appears as a flattened twisted tube. 50

52. The degree of twist is a result of the type of environment the plant is grown in, the specific species or cultivar, and the ripeness of the “fibers”.
The twists cause the “fibers” to cling to each other and improve their spinning qualities. 51

53. JUTE Jute is the bast fiber obtained from the secondary phloem of plants called Corchorus capsularis and Corchorus olitorius .
Their fiber is cheaper than cotton and flax.
The plant is tall slender annual one with shrubby nature. The fibre surrounds the woody central part of the stem. In fact, it is located in wedge-shaped bundles outside the xylem. 52

54. Fibres are grouped in concentric rings alternating with the thin walled tissue.
This thin walled phloem tissue breaks up through microbiological decomposition during retting. At maturity, these fibres lose their protoplasm and become dead. Corchorus olitorius Corchorus capsularis 53

55. They are elongated, unbranched, sclerenchymatous cells with very thick cell walls. These fibres are longer than a meter in comparison to the fibres in fruits or seeds. The stem is retted in water and the long fibers are separated from the phloem part.
The pale yellow fibers are obtained during this process.
Jute is used to produce rough wearing, bags, sacs and wrapping materials for textile industry.
The fibers are twisted to produce twine, coarse cloth, and curtains, manufacture of paper etc.
India is the best producer of jute. 54

56. COIR Coir is a hard, versatile, natural fibre. The coir is obtained from the mesocarp of the fruit. Coir fibre is generally not very long (0.15—0.28 m). The coir fibre is multicellular (the fibre contains 30 to 300 or more cells in its total cross-section) and its cross-section is polygonal or round. The transverse and longitudinal section of coir fibre, shows the number of cells and distribution of cells around the central pore called ‘lacuna’. 55

57. The walls are thin to fairly thick with lense-shaped silicified stegmata on their surface. These are delicate thickenings with a few of them being circular or spiral in shape.
There is a central cavity in each cell called lumen, which is medium to large in size (polygonal, round or rounded to elliptic in shape). 56

58. The surface of the individual cell is smooth or rough with certain defects like cross-markings, while the surface of the fibre is coated with a waxy material called cuticle.
The chemical constituents of pure coir fibre have been found to be cellulose, lignin, hemicellulose, pectin and water solubles. The ageing of the fibres is found to render the fibres stiffer and tougher, and leads to an increase in the lignin content
Coconut husk is retted and the fibers are entangled by beating.
Coir fiber has various uses like making mats, carpets, cordage, brushes etc. 57

59. REFERENCE Cutter, E. (1978). Plant Anatomy Part I. Reading, Mass.: Addison-Wesley Pub. Co. Esau, K. (1965). Plant anatomy. Plant Anatomy., (2 nd Edition). Fahn, A. (1977). Plant Anatomy. Oxford: Pergamon Press. Foster, A. (1949). Practical Plant Anatomy. New York: D. Van Nostrand Co. Pandey, B. (1996). Plant Anatomy. New Delhi: S Chand & Comp. Pandey, S. N., & Chadha, A. (2009). Plant anatomy and embryology. Vikas Publishing House. Satyanarayana, K. G., Kulkarni, A. G., & Rohatgi, P. K. (1981). Structure and properties of coir fibres. Proceedings of the Indian Academy of Sciences Section C: Engineering Sciences, 4, 419-436. https://labs.plb.ucdavis.edu/rost/cotton/reproduction/frfiber.html 58

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