Fiber phloem

Types of twined fabric structures composed of bast or phloem fibers and feathers were identified in prehistoric fabrics of southeastern North America by chemical and physical analyses and technical fabrication studies. Fabrics and either partially or completely mineralized pseudomorphs after fabric from the Tunacunnhee and Etowah sites in Georgia (dated respectively A.D. 150 95 years and about A.D. 1200) were examined. The work confirms the presence of at least two types of twined structures for the earlier Hopewell site and intricately constructed re-plied yarns and twined fabric for the later Mississippian one. The study of fabrics from both sites provides evidence of the kinds of materials produced and used by prehistoric peoples of the region during a 1000-year interlude. 

Radial fibro-vascular bundle of four, rarely two or three or five or six phloem patches alternating with as many xylem arms. Not uncommon to find bast or phloem fiber along outer face of each phlUem patch. Xylem has spiral tracheae, internal to these a few pitted vessels, then, as- root ages, more pitted vessels, also xylem cells and wood fibers make their appearance. ... 

Jute and kenaf fibers develop in the phloem, or bast, region of the stem of the plants, and they appear as wedge-shaped bundles of cells intermingled with parenchyma cells and other soft tissues (Figure 7.1) in the transverse sections of the stem. In the growing part of the stem, a circumferential layer of primary fibers develops from the protophloem, but, as vertical growth ceases in the lower parts, secondary phloem fibers develop as a result of cambial activity. In mature plants, which reach a height of 2.5-3.5 m and a basal diameter of about 25 mm, the secondary fiber accounts for about 90% of the total fiber bundles. 

Similar sequential development is seen in secondary phloem fibers. At 63 days after planting, there is little thickening of the fiber wall and the fibers thicken gradually with maturity from 73 days to 112 days after planting. 

Fibrous plant Phloon content in dry straw (%) Fiber ctmtent in phloem (%) Fiber content in dry straw (%)... 

In his elegant study of hormonal control of the normal differentiation of phloem fibers (described below), Aloni (1976) pointed out that the fibers did not differentiate from the parenchymatous cells of the wound callus, even though sieve tubes and tracheary cells did. The differentiation of phloem fibers was always limited to the longitudinal vascular strands, never being found in the intervening parenchyma. In that sense, one could say that they do not regenerate however, their regeneration has been seldom studied. 

Aloni took up the problem of fiber differentiation and developed a physio-logical-anatomical approach, which, when combined with multiple-comparison statistics, resulted in two excellent papers (1976, 1979). Concentrating on the primary phloem fibers of Coleus, he used a technique of staining cleared material (Aloni and Sachs 1973) which allowed large samples to be processed efficiently. 

Fig. 4.10 A-F. Diagrams illustrating the effects of various treatments on the differentiation of phloem fibers in Coleus stems. Numbers beside the internodes show the average number of fibers ( standard error) in the adjacent half transverse section. The plants of diagram A were untreated. On the day the A plants were collected, the axillary shoots and indicated leaves of the other treatments were excised. Plants of B F were harvested 2 weeks later. (Aloni 1976)...

Substitution of lAA, GA3, or both for all the leaves and for the stem above internode 5 revealed that lAA alone could restore about 13% of the normal number of phloem fibers in internode 5, GA3 alone had no effect, but lAA and GA3 added together at 0.05% in lanolin restored the full normal number of differentiated fibers (Fig. 4.11, Aloni 1979). Increasing the concentration of GA3 in the lAA-GA lanolin produced longer fiber cells, as might be expected from the earlier literature reporting GA3 effects on intact plants. 

Fig. 4.11 A-F. The effect of lAA, GA3, or both in replacing the effect of superjacent leaves in causing the differentiation of phloem fibers in Coleus stems. (Aloni 1979)...

Aldaba VC (1927) The structure and development of the cell wall in plants. I. Bast fibers of Boehmeria and Linum. Am J Bot 14 16-24 Aloni R (1976) Polarity of induction and pattern of primary phloem fiber differentiation in Coleus. Am J Bot 63 877-889... 

Aloni R (1979) The role of auxin and gibberellin in differentiation of primary phloem fibers. Plant Physiol 63 609-614... 

Sorokin HP, Mathur SN, Thimann KV (1962) The effects of auxins and kinetin on xylem differentiation in the pea epicotyl. Am J Bot 49 444-453 Stant MY (1961) The effect of gibberellic acid on fibre-cell length. Ann Bot 25 453-462 Stant MY (1963) The effect of gibberellic acid on cell width and the cell wall of some phloem fibers. Ann Bot 27 185-196... 

Vegetable fibers are classified according to their source ia plants as follows (/) the bast or stem fibers, which form the fibrous bundles ia the inner bark (phloem or bast) of the plant stems, are often referred to as soft fibers for textile use (2) the leaf fibers, which mn lengthwise through the leaves of monocotyledonous plants, are also referred to as hard fibers and (J) the seed-hair fibers, the source of cotton (qv), are the most important vegetable fiber. There are over 250,000 species of higher plants however, only a very limited number of species have been exploited for commercial uses (less than 0.1%). The commercially important fibers are given ia Table 1 (1,2). 

The aim of our project was to study phloem as a source of fiber and polyphenols, and to develop a method to improve its taste without losing the potentially bioactive polyphenols. In addition, we wanted to investigate the bioavailability, cholesterolemic and antioxidative effects and safety of phloem and its phytonutrients in humans in a randomised double-blind trial. 

When compared to whole meal rye flour (280 kcal/1160 kJ) and to wheat flour (320 kcal/1320 kJ), phloem powder (140 kcal/580 kJ) contains approximately 50% less energy. As is typical for all flours, phloem powder also contains a low amount of fat (total amount 2.3 g/100 g). The protein content of phloem is only 2.5 g (per 100 g), whereas the respective amount in whole meal rye flour is 8.8 g and in wheat flour 12.1 g. The content of carbohydrates in phloem ( 30 g/100 g) is about 50% less than in rye (55 g) and wheat flours (59 g). The relatively low energy, protein and carbohydrate content of phloem when compared with commonly used flours, is related to its high content of different fiber. Detailed nutritional data for phloem and phloem breads used in our trial are presented in Table 14.1. 

Phloem powder is rich in different types of fibers, lignans and polyphenols (Table 14.1). Phloem contains 58 g of fiber per 100 g, of which 51 g is insoluble and a lesser amount ( 7 g) is water-soluble. The total amount of different lignans in phloem is 79.3 mg/100 g, consisting mainly (98%) of secoisolariciresinol. The main flavonoids in phloem are catechins, and the... 

Subjects were randomly assigned to consume daily 70 g of normal dried rye bread (placebo group, = 30), rye bread in which 8% of the rye flour was substituted with phloem powder (low phloem, LP, group, = 30) or bread in which 14% of the rye flour was substituted with phloem powder (high phloem, HP, group, n = 15). Study breads used in our study were different in fiber, lignan and catechin content. The nutrient content of the phloem powder and... 

In our study, consumption of rye bread or rye bread with phloem did not have an effect on serum lipids (total, LDL or HDL cholesterol or triglycerides) (Table 14.4). This is contrary to a recent finding suggesting that soluble fiber from rye bread decreased the concentrations of cholesterol (Leinonen et al., 2000). In that study ingestion of rye bread (220 g/d) with naturally high amounts of insoluble (18 g/d) and soluble fiber (4 g/d) decreased the LDL concentrations by 8% in hypercholesterolemic men. The researchers speculated that soluble fiber, maybe P-glucan, was responsible for the hypocholesterolemic effect. The amount of rye bread (70 g/d vs 220 g/d), the amount of total (5.9-11.8 g/d vs 22.1 g/d) and soluble fiber (0.6-1.3 g/d vs 4 g/d) ingested in this study was considerably less, and could explain the lack of effects on blood lipids in our study. 

Bast is the inner bark of a plant, composed of the phloem and other fibrous cells. Hard fiber, which comes from leaves, is used mostly for cordage (rope, twine, cord) and the rough fabric used for making sacks and other containers. Soft fiber, which comes from plant stems, is used to make thread and finer fabrics like linen, cotton, and woven hemp. 

Figure 1-3. Idealized longitudinal section through part of a vascular bundle in a stem, illustrating various anatomical aspects of the xylem and the phloem. New cells forming in the xylem initially contain cytoplasm, which is lost as the cells mature and become conducting. Fiber cells, which occur in the xylem, are usually quite tapered and provide structural support. The nucleated companion cells are metabolically involved with the sieve-tube members of the phloem.

On transverse section of the pedicel, two kinds of laticifers, a convex arc and a concave one, were observed in the peripheral bundle and in the central one, respectively. The placenta traces (placentae) and the valve traces (valves) through the capsule wall appeared light microscopically as dense masses of branching vascular tissues in chlorenchyma within the epicarp. The former were fewer in number and smaller in diameter than the latter. The placenta traces contained laticifers but no fibers. The valve traces became the main source of latex. No laticifers were detected in the ovule however, the terminals of the laticifers were observed near the junction of the placenta and ovule. Laticifers appeared in the phloem of the sepals and petals during blooming. Laticifers were detected in the stamen traces in the thalamus but not in the stamens. The ends of laticifers were detected in ovule traces. The diameters of laticifers in the ovary 2 weeks before petal fall were as large as those in the mature capsule. 

Fig. 38.—Various forms of calcium oxalate crystals. A, styloids from the bark of QuiUaja saponaria B, rosette aggregate from rhizome of Rheum officinale C, raphide from the bulb of Urginea maritima D. crystal fiber as seen in longitudinal section in either the xylem or phloem regions of Glycyrrhiza E, microcrystals (crystal sand) isolated from the parenchyma of Belladonna root F, monoclinic prisms and G, twin-crystals from leaves of Hyoscyamus niger. All highly magnified.

Phloem is that part of a fibro-vascular bundle that contains sieve tubes, phloem cells, and often bast fibers. 

A radial fibro-vascular bundle of many alternating xylem and phloem patches and hence polyarch. The phloem tissue consists of phloem cells and sieve tubes. The xylem is composed of xylem cells, tracheae and wood fibers. 

At about six weeks one. notes cells, dividing by tangential walls in the inner curve of phloem patches. This is in-trafascicular cambium. A single layer of flattened cells starts to cut off on its inner side a quantity of secondary xylem and pushes out the patches of bast fibers, adds a little secondary phloem on the outer side. Secondary... 

Pig. 64.—Photomicrograph of a transverse section of an old portion of California Privet root, showing completed secondary development. Note the prominent medullary rays (mr) cork (cfe) phellogen (,ph) secondary cortex (between ph and p ) protophloem (p )i secondary phloem ( ) cambium (c) secondary xylem tracheae (0 wood fibers (w/) and piotoxylem ( ). 

Secondary Phloem Soft Bast—phloem cells and sieve tubes. Cambium—active layer giving rise to secondary phloem on outer and secondary xylem or inner face, and adding to depth of med. rays. Secondary xylem—wood fibers, pitted vessels, tracheids. 

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