| 1. |
- Prashant, S., et al.
(author)
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Down-regulation of Leucaena leucocephala cinnamoyl CoA reductase (LlCCR) gene induces significant changes in phenotype, soluble phenolic pools and lignin in transgenic tobacco
- 2011
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In: Plant Cell Reports. - : Springer Nature. - 0721-7714 .- 1432-203X. ; 30:12, s. 2215-2231
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Journal article (peer-reviewed)abstract
- cDNA and genomic clones of cinnamoyl CoA reductase measuring 1011 and 2992 bp were isolated from a leguminous pulpwood tree Leucaena leucocephala, named as LlCCR. The cDNA exhibited 80–85% homology both at the nucleotide and amino acid levels with other known sequences. The genomic sequence contained five exons and four introns. Sense and antisense constructs of LlCCR were introduced in tobacco plants to up and down-regulate this key enzyme of lignification. The primary transformants showed a good correlation between CCR transcript levels and its activity. Most of the CCR down-regulated lines displayed stunted growth and development, wrinkled leaves and delayed senescence. These lines accumulated unusual phenolics like ferulic and sinapic acids in cell wall. Histochemical staining suggested reduction in aldehyde units and increased syringyl over guaiacyl (S/G) ratio of lignin. Anatomical studies showed thin walled, elongated xylem fibres, collapsed vessels with drastic reduction of secondary xylem. The transmission electron microscopic studies revealed modification of ultrastructure and topochemical distribution of wall polysaccharides and lignin in the xylem fibres. CCR down-regulated lines showed increased thickness of secondary wall layers and poor lignification of S2 and S3 wall layers. The severely down-regulated line AS17 exhibited 24.7% reduction of Klason lignin with an increase of 15% holocellulose content. Contrarily, the CCR up-regulated lines exhibited robust growth, development and significant increase in lignin content. The altered lignin profiles observed in transgenic tobacco lines support a role for CCR down-regulation in improving wood properties of L. leucocephala exclusively used in the pulp and paper industry of India.
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| 2. |
- Sirisha, V. L., et al.
(author)
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Cloning, characterization and impact of up- and down-regulating subabul cinnamyl alcohol dehydrogenase (CAD) gene on plant growth and lignin profiles in transgenic tobacco
- 2011
-
In: Plant growth regulation (Print). - : Springer Nature. - 0167-6903 .- 1573-5087. ; 66:3, s. 239-253
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Journal article (peer-reviewed)abstract
- Both cDNA including 5′UTR and 3′UTR and genomic clones of cinnamyl alcohol dehydrogenase (CAD) were isolated and characterized from a pulp-yielding leguminous tree Leucaena leucocephala (LlCAD1). The deduced amino acid sequence shared high identity with orthologous sequences of Acacia mangium × Acacia auriculiformis (83%), Medicago sativa (83%), Nicotiana tabaccum (83%) and Aralia cordata (81%). Full length cDNA contained 78 bases of 5′UTR and 283 bases of 3′UTR, while the genomic clone contained 5 exons and 4 introns. Western blot analysis revealed elevated expression of LlCAD1 in seedling roots and shoots compared to leaves. Sense and antisense CAD tobacco transgenics showed increased and reduced CAD activity accompanied by a change in monomeric lignin composition. Histochemical staining of lignin in down-regulated plants suggested an increase in aldehyde units and a decrease in S/G ratio. Down-regulation of CAD resulted in accumulation of syringic, ferulic, p-coumaric and sinapic acids compared to untransformed controls. These observations were validated by anatomical studies of down-regulated transgenic stems which showed thin walled, elongated phloem and xylem fibres, accompanied by a reduction in the density of vessel elements and amount of secondary xylem when compared to untransformed plants. Furthermore, Klason lignin analysis of CAD antisense transgenics showed 7–32% reduced lignin and normal phenotype as compared to untransformed plants. Such a reduction was not noticed in up-regulated transgenics. These results demonstrate a unique opportunity to explore the significant role that down-regulation of CAD gene plays in reducing lignin content thereby offering potential benefits to the pulp and paper industry.
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| 3. |
- Sivan, Pramod, 1984-, et al.
(author)
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Distribution of tension wood like gelatinous fibres in the roots of Acacia nilotica (Lam.) Willd
- 2014
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In: Planta. - : Springer. - 0032-0935 .- 1432-2048. ; 240:6, s. 1191-1202
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Journal article (peer-reviewed)abstract
- The present study was aimed to investigate the anatomy of reaction xylem in the positively gravitropic roots of Acacia nilotica growing in compact and waterlogged soils. The roots collected from the two different sites showed occurrence of gelatinous fibres throughout xylem radii from a distance of 4 cm from the soil surface. The thickness of gelatinous layer (G-layer) increased in the root collected from the deeper soil. Further, the ultrastructural studies revealed a complete replacement of S2 and S3 layers in G-fibres nearer to root tip region as compared to the root portion close to upper part of the soil surface. In addition, these fibres demonstrated intense lignification in compound middle lamellae region of G-fibre walls. Moreover, the vessel density and their width increased considerably near the root tip region. The immunofluorescence analysis suggested that the β-1,4-galactans were prevalent in G-layer, whereas the xylan was restricted to only regions of lignified secondary wall. The similarities in distribution pattern and anatomical features of G-fibres in waterlogged and non-waterlogged roots suggest the occurrence of G-fibres as inherent characteristics in the roots of Acacia nilotica.
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| 4. |
- Mishra, Preeti, et al.
(author)
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Effect of exogenous growth regulators on secondary vascular tissue differentiation in the twigs of Kigelia africana
- 2013
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In: Phyton - Annales Rei Botanicae. - Horn, Austria : Verlag Berger. - 0079-2047. ; 53:1, s. 133-149
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Journal article (peer-reviewed)abstract
- The effect of gibberellic acid (GA), naphthalene acetic acid (NAA) and ethephon on dormant and actively growing twigs of was studied by histological and histochemical staining methods. Application of GA and ethephon alone on dormant twigs did not initiate cambial cell division and differentiation, while application of NAA lead to cambial cell division but failed to differentiate cells towards xylem and phloem. Application of GA together with NAA and the combination of GA, NAA and ethephon induced rapid cambial cell division and differentiation of xylem and phloem elements. In the upper portion of twigs close to the point of GA, NAA and ethephon application the cell walls of cambium and phloem elements underwent lignification, while formation of earlywood and latewood was observed in the lower portion. Moreover the application of this hormone combination on actively growing twigs resulted in the formation of tyloses in vessels and differentiation of parenchyma cells with intercellular spaces towards phloem. The combination of GA-NAA promoted rapid cambial cell division and differentiation towards xylem. Maule’s reaction revealed increase in ‘S’ type of lignin in the walls of newly formed vessels and associated parenchyma cells following GA+NAA treatment.
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| 5. |
- Patel, Vinay, et al.
(author)
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Development of vascular cambium in the leaf rachis of Kigelia Africana (Lam.) Benth
- 2010
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In: PRAJÑĀ - Journal of Pure and Applied Sciences. - Gujarat, India : Sardar Patel University. - 0975-2595. ; 18:1-4, s. 40-43
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Journal article (peer-reviewed)abstract
- The structural changes during the vascular cambium development from procambium in the leaf rachis of Kigelia africana bearing leaflets of different developmental stages (young, mature and old rachis) were investigated. The different regions from the internodes of rachis bearing young, copper brown coloured leaves revealed the sequential stages of cambial development. Terminal region of the rachis showed developing procambium along with protoxylem and protopholem derivatives, middle regions exhibited the development of interfascicular cambium whereas basal region showed complete ring of vascular cambium with secondary phloem derivatives. Rachis bearing brownish coloured leaflets showed an active cambium with both secondary xylem and phloem derivatives indicating bidirectional cambial growth. Rachis with fully matured dark green leaflets was characterized by the presence of dormant cambium surrounded by mature xylem and phloem elements and occurrence of calcium oxalate crystals in the phloem parenchyma cells. The study also describes the pattern of vascular cambial development in the leaf rachis of Kigelia, a deciduous tree and it was compared with development of vascular cambium in the leaves of conifers and evergreen dicotyledons. Influence of leaf maturity on cambial activity and secondary xylem development is discussed.
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| 6. |
- Patel, Vinay R., et al.
(author)
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Cambial activity, annual rhythm of xylem production in relation to phenology and climatic factors and lignification pattern during xylogenesis in drum-stick tree (Moringa oleifera)
- 2014
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In: Flora. - : Elsevier. - 0367-2530 .- 1618-0585. ; 209:10, s. 556-566
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Journal article (peer-reviewed)abstract
- The interrelationship among seasonality of cambium, wood formation, cell size variation, lignification, tree phenology and climatic factors has been examined in Moringa oleifera, a tropical evergreen tree. The vascular cambium in Moringa is a storied with a distinct seasonal variation in its structure due to dimensional changes in rays. Though cambium remains active throughout the year it is sensitive to water availability. Peak cambial cell division and rate of xylem differentiation are influenced by average rainfall during the monsoon period. Cambial cell division reaches higher up in the tree trunk when it is supporting a high number of branches and leaves. Statistical analysis of cell size variation and climate factors revealed that xylem cell development is greatly influenced by rainfall and rarely by temperature. Lengths of fusiform initials and vessel elements are positively correlated. The pattern of lignification during xylogenesis shows that the vessels are the first element to develop lignified walls and ray cells are the last elements to become lignified. Fiber cell walls show more syringyl lignin, while the cell walls of other xylem elements are characterized by relatively more guaiacyl lignin units.
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| 7. |
- Rao, Karumanchi S., et al.
(author)
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Ultrastructural Changes in the Cell Walls of Cambial Derivatives During Wood Formation in Indian ELM (Holoptelea Integrifolia)
- 2012
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In: IAWA Journal. - : Brill. - 0928-1541 .- 2294-1932. ; 33:4, s. 403-416
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Journal article (peer-reviewed)abstract
- Sequential changes occurring in cell walls during expansion, secondarywall (SW) deposition and lignification have been studied in the differ-entiating xylem elements of Holoptelea integrifolia using transmissionelectron microscopy. The PATAg staining revealed that loosening of thecell wall starts at the cell corner middle lamella (CCmL) and spreads to ra-dial and tangential walls in the zone of cell expansion (EZ). Lignificationstarted at the CCML region between vessels and associated parenchymaduring the final stages of S2 layer formation. The S2 layer in the vesselappeared as two sublayers,an inner one and outer one.The contact raycells showed SW deposition soon after axial paratracheal parenchyma hadcompleted it, whereas noncontact ray cells underwent SW deposition andlignification following apotracheal parenchyma cells. The paratrachealand apotracheal parenchyma cells differed noticeably in terms of propor-tion of SW layers and lignin distribution pattern. Fibres were found tobe the last xylem elements to complete SW deposition and lignificationwith differential polymerization of cell wall polysaccharides. It appearsthat the SW deposition started much earlier in the middle region of thefibres while their tips were still undergoing elongation. In homogeneouslignin distribution was noticed in the CCML region of fibres.
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| 8. |
- Sivan, Pramod, 1984-, et al.
(author)
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Anatomical Changes During Transition from Juvenile to Adult Wood in Branch and Main Trunk Xylem of Subabul (Leucaena leucocephala[Lam.] de Wit)
- 2012
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In: Journal of Sustainable Forestry. - : Taylor & Francis. - 1054-9811 .- 1540-756X. ; 31:7, s. 661-673
-
Journal article (peer-reviewed)abstract
- The anatomical changes occurring during transition from juvenile to mature wood were studied in the branch and main trunk of Leucaena leucocephala. To confirm the wood maturity in the 5-yr-old tree, the anatomical features were compared with the adult wood collected from the main trunk of a 15-yr-old tree. In both the branch and wood of the trunk, most of the anatomical features—such as increase in dimensions of fibers and vessel elements, and decrease in frequency of vessel elements and rays—were gradual during radial growth from pith to periphery. A noticeable anatomical change is observed in the transition of triseriate rays to multiseriate rays in the region of wood which is about 5.5 cm away from the pith. The ray dimensions and anatomical features of other elements from the periphery of the branch and 5-yr-old trunk xylem match with that of 15-yr-old main trunk wood. This indicates that in both the branches and main trunk of Leucaena, transition from juvenile to adult or mature wood occurs after the trees have attained 14 cm radial growth.
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| 9. |
- Sivan, Pramod, 1984-, et al.
(author)
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Definitive Callose Deposition in Tapping Panel Dryness Affected Bark of Hevea brasiliensis
- 2011
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In: Journal of Sustainable Forestry. - : Informa UK Limited. - 1054-9811 .- 1540-756X. ; 30:4, s. 329-342
-
Journal article (peer-reviewed)abstract
- The structural and functional aspects of sieve elements in Tapping Panel Dryness (TPD) affected bark of Hevea brasiliensis, with special reference to definitive callose deposition, have been studied using histochemical methods. The effect of ethephon in definitive callose deposition in TPD affected bark also has been investigated, as the ethylene is reported to have a major role in TPD. The phloem of Hevea is characterized by sieve elements with compound sieve plates. The deposition of definitive callose on the sieve areas following TPD limits the translocation of sap through sieve elements. The amount of functional phloem was narrow and the accumulation of definitive callose was more in the sieve elements of TPD affected bark compared to that of unaffected bark of the same tree and of healthy trees. The affected area showed an increment in deposition of definitive callose in both vertical and horizontal extent of sieve areas; and there was a reduction in length of sieve plate, density of sieve pores, length of inter-sieve area wall, and number of sieve element rows in the inner bark. The lateral walls of non-functional sieve elements became thick and lignified. The anatomical changes in the sieve elements of TPD affected bark suggest that the translocation of phloem sap is regulated by deposition of definitive callose and less differentiation of sieve elements from vascular cambium. The external application of ethephon on bark enhanced the definitive callose deposition on sieve elements. The findings from the study reveal that ethylene plays a major role in the senescence of sieve elements.
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| 10. |
- Sivan, Pramod, 1984-, et al.
(author)
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Effect of 2,6-Dichlorobenzonitrile (DCB) on Secondary Wall Deposition and Lignification in the Stem of Hibiscus Cannabinus L.
- 2013
-
In: Journal of Plant Development. - : Editura Universitatii Alexandru Ioan Cuza din Iasi. - 2065-3158. ; 20, s. 25-33
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Journal article (peer-reviewed)abstract
- Light and electron microscopic studies were carried out on the secondary xylem of actively growing shoots of Hibiscus cannabinus treated with cellulose synthesis inhibitor 2,6-dichlorobenzonitrile (DCB). Treatment with 20μM DCB induced differentiation of xylem fibres with thin secondary walls and parenchyma cells with abnormal wall thickening and lignification. At concentration above 50 μM resulted in the disappearance of cambial zone, inhibition of secondary wall deposition, lignification of primary walls, deformed vessel walls and dispersed lignin distribution in secondary walls. Transmission electron microscopic study revealed the initiation and formation of large intercellular spaces between the walls of differentiating xylem elements. Abnormal pattern of wall deposition and inhomogeneous lignin distribution was evident in fibres and vessel. The length and width of both fibres and vessel elements were reduced significantly even with lower concentrations of DCB.
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| 11. |
- Sivan, Pramod, 1984-, et al.
(author)
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Ethylene and its interaction with other hormones in tension wood formation in Leucaena leucocephala (Lam.) de Wit
- 2012
-
In: Journal of the Indian Academy of Wood Science. - : Springer. - 0972-172X .- 0976-8432. ; 9:2, s. 130-139
-
Journal article (peer-reviewed)abstract
- The effect of exogenous ethephon and its combination with gibberellic acid (GA3), indole-3-acetic acid (IAA) and benzyl amino purine (BAP) on tension wood formation in the vertically growing shoots of Leucaena leucocephala has been studied using light and scanning electron microscopy (SEM). The application of exogenous ethephon induced tension wood formation. The percentage of tension wood severity in the shoots was directly proportional to the concentration of ethephon applied. SEM studies revealed the replacement of S2 and S3 fibre wall layers with the gelatinous layer (G-layer) in response to high concentration of ethephon. Ethephon exhibited synergistic interaction with GA3 and BAP in tension wood formation. Fibres and vessel elements in tension wood, induced by ethylene and its combination with other hormones showed increase or decrease in their dimensions irrespective of their concentration and combination. The density of rays increased in all the treatments except in the combination of ethephon and IAA. The anatomical data indicate that ethylene plays a major role in tension wood formation and it interacts synergistically with gibberellins and cytokinin. On the other hand, such synergistic interaction was not found between ethephon and IAA in tension wood formation.
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| 12. |
- Sivan, Pramod, 1984-, et al.
(author)
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Influence of exogenous ethylene on cambial activity, xylogenesis and ray initiation in young shoots of Leucaena leucocephala (lam.) de Wit
- 2013
-
In: Flora. - : Elsevier. - 0367-2530 .- 1618-0585. ; 208:10-12, s. 549-555
-
Journal article (peer-reviewed)abstract
- The effect of exogenous ethephon on cambial activity, xylem production and ray population in young shoots of Leucaena leucocephala was investigated anatomically. The application of ethephon showed a diphasic effect on cambial activity and xylogenesis in a dose dependent manner. Lower concentration of ethephon enhanced cambial activity while high concentrations reduced cambial cell divisions and daughter-cell differentiation. High ethephon concentration also resulted in shorter vessel elements, thick walled fibers and phenolic accumulation in ray cells and vessel elements, whereas low concentration allowed elongation of fibers and vessel elements. The density of rays increased significantly with increase in ethylene concentration. The evaluation of longitudinal sections of cambial zone in ethephon treated plants showed high frequency of transformation of fusiform initials into ray initials through divisions and segmentation, resulting in high ray frequency in both xylem and phloem. The present study demonstrates that ethylene plays an important role in regulating secondary vascular tissue composition by reducing the population of fusiform initials in the cambium.
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| 13. |
- Sivan, Pramod, 1984-, et al.
(author)
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Occurrence of Reaction xylem in the peduncle of Couroupita Guianensis and Kigelia Pinnata
- 2010
-
In: IAWA Journal. - : Brill. - 0928-1541 .- 2294-1932. ; 31:2, s. 203-216
-
Journal article (peer-reviewed)abstract
- The anatomy of the secondary xylem and distribution pattern of gelatinous fibres (G-fibres) have been studied in the developing and heavy fruitbearing mature peduncles of Kigelia pinnata and Couroupita guianensis.The peduncle in both the plants developed reaction xylem as a result ofgrowth stresses caused by development of large fruits. In Couroupitapeduncles which are originally horizontal, G-fibre distribution was uni-lateral and similar to that of typical tension wood whereas the hangingKigelia peduncles have uniformly distributed gelatinous fibres throughoutthe xylem. The tension xylem severity was higher in the basal region anddecreased towards the terminal region of the current year’s peduncle butafter fruit development a drastic increase in tension wood severity wasobserved in the terminal region. In the Kigelia peduncles, tension woodseverity in terms of G-layer proportion to lignified wall was found to beless than in Couroupita. The abundance of vessels decreased with highfrequency of gelatinous fibres in Couroupita. The peduncle of Kigelia ischaracterized by high vessel frequency, thin normal fibre walls, and thickouter walls with thin gelatinous layer in tension wood fibres. Dimensionalvariations were also noticed in the mechanical and conducting elementsvarying with tension wood severity.
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| 14. |
- Sivan, Pramod, 1984-, et al.
(author)
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Structural and dimensional changes in the cambium of tapping panel dryness affected trees of Hevea brasilensis
- 2011
-
In: Phyton - Annales Rei Botanicae. - : Berger and Sohne. - 0079-2047. ; 51, s. 231-244
-
Journal article (peer-reviewed)abstract
- The structural changes associated with the cambium of bark area affected by tapping panel dryness (TPD) have been studied in Hevea brasiliensis and compared with those of unaffected bark area of the same tree and that of TPD unaffected (healthy) trees. A number of structural deformations and dimensional changes occurred in the cambial zone cells including the altered cambial activity in the affected area. The cambium is nonstoried with elongated fusiform initials having actively growing tips enclosing uni or multiseriate rays. The anatomical features of cambium in relation to the structural changes in the affected trees were studied by observing the alignment of cells in the cambial zone. The changes in the cambial zone of affected area of bark include shortening of fusiform cambial cells, increase in the number of cambial rays, number of terminal cell of ray, width of ray and number of cell layers constituting the cambial zone. In the affected bark, fusiform cambial cells underwent transformative division leading to increment in the width and height of cambial rays. While in the TPD affected trees with warty outgrowth, the height of ray cambial cells decreased drastically and showed an increase in their width and density. The effect of ethylene in triggering the structural symptoms associated with TPD has also been studied as the ethephon application is a common practice in rubber plantations to stimulate the latex yield. In healthy trees, ethephon stimulation enhanced the cell divisions and length of fusiform cambial cells. The stimulation on the affected bark resulted in triggering of structural aberrations in the cambial zone cells. The effect of permanently altered cambial activity on the differentiation of laticifier system with respect to TPD has been discussed.
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| 15. |
- Sivan, Pramod, 1984-, et al.
(author)
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Structural, histochemical and chemical characterization of normal, tension and opposite wood of Subabul (Leucaena leucocephala (lam.) De wit.)
- 2013
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In: Wood Science and Technology. - : Springer. - 0043-7719 .- 1432-5225. ; 47:4, s. 777-796
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Journal article (peer-reviewed)abstract
- Structure, histochemistry and chemical composition of tension (TW), opposite (OW) and normal wood (NW) of Leucaena leucocephala have been studied using histological, histochemical and biochemical methods. TW vessels are longer and have a larger diameter than NW vessels, and the rays are shorter and thinner. The G-layer replaced S3 and parts of S2 wall layers in TW fibres. TW further contained less lignin that also had a lower syringyl-to-guaiacyl ratio. The lignin was also more condensed. The content of α-cellulose was high in TW. TW contains hemicelluloses and pectins composed of more galactose, and less xylose, mannose, 4-O-methylglucuronic acid and galacturonic acid compared to that of OW. This study suggests that in the TW of Leucaena, the amount and composition of lignin, hemicelluloses and pectins differ considerably from that in OW and NW.
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| 16. |
- Thomas, Vinoth, et al.
(author)
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Structural modifications of phloic rays in Hevea brasiliensis with reference to tapping panel dryness and stimulation
- 2013
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In: Journal of Plantation Crops. - India : Society for Plantation Crops. - 0304-5242 .- 2454-8480. ; 41:2, s. 142-150
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Journal article (peer-reviewed)abstract
- Hevea brasiliensis, the prime source of natural rubber, when tapped intensively showed the symptoms of gradual cessation of latex flow from the tapping wound and this phenomenon is termed as tapping panel dryness (TPD), leading to a number of structural deformations in the bark tissues. The unproductive bark thus formed due to TPD is subjected to ethephon stimulation resume latex flow for a period. The study was initiated to trace the structural modifications occurred in phloic rays as an alternative route for translocation under necessity. The dimension of phloic rays also showed significant variation in TPD trees in comparison with both healthy stimulated trees. A decrease in length and an increase in width of phloic rays were evident in TPD affected trees over healthy trees. Average height of ray (µm) in the bark of healthy, TPD affected, unaffected zone above the TPD affected area and TPD panel under ethephon was 495, 259, 416 and 285 respectively. In healthy trees, 57 per cent of the rays fall in the stratified height class of 300-500 µm but in TPD trees, 78 per cent of the phloic rays is having a height less than 300 µm. The average width of the ray measured 56.81 and 74.25 µm respectively for healthy and TPD trees. In healthy trees 61 per cent of the ray falls under width strata of 40-60 µm and in TPD trees 68 per cent is in the 60-80 and 24 per cent in 80-100 µm width strata. For the production of latex from unproductive bark of TPD tree on stimulation, adequate nourishments is being mobilized to the site of action by strengthening radial transport system in the affected area.
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| 17. |
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