| 1. |
- Prashant, S., et al.
(författare)
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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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Ingår i: Plant Cell Reports. - : Springer Nature. - 0721-7714 .- 1432-203X. ; 30:12, s. 2215-2231
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Tidskriftsartikel (refereegranskat)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.
(författare)
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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
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Ingår i: Plant growth regulation (Print). - : Springer Nature. - 0167-6903 .- 1573-5087. ; 66:3, s. 239-253
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Tidskriftsartikel (refereegranskat)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.
(författare)
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Distribution of tension wood like gelatinous fibres in the roots of Acacia nilotica (Lam.) Willd
- 2014
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Ingår i: Planta. - : Springer. - 0032-0935 .- 1432-2048. ; 240:6, s. 1191-1202
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Tidskriftsartikel (refereegranskat)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.
(författare)
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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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Ingår i: Phyton - Annales Rei Botanicae. - Horn, Austria : Verlag Berger. - 0079-2047. ; 53:1, s. 133-149
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Tidskriftsartikel (refereegranskat)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.
(författare)
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Development of vascular cambium in the leaf rachis of Kigelia Africana (Lam.) Benth
- 2010
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Ingår i: PRAJÑĀ - Journal of Pure and Applied Sciences. - Gujarat, India : Sardar Patel University. - 0975-2595. ; 18:1-4, s. 40-43
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Tidskriftsartikel (refereegranskat)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.
(författare)
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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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Ingår i: Flora. - : Elsevier. - 0367-2530 .- 1618-0585. ; 209:10, s. 556-566
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Tidskriftsartikel (refereegranskat)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.
(författare)
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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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Ingår i: IAWA Journal. - : Brill. - 0928-1541 .- 2294-1932. ; 33:4, s. 403-416
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Tidskriftsartikel (refereegranskat)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.
(författare)
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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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Ingår i: Journal of Sustainable Forestry. - : Taylor & Francis. - 1054-9811 .- 1540-756X. ; 31:7, s. 661-673
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Tidskriftsartikel (refereegranskat)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.
(författare)
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Definitive Callose Deposition in Tapping Panel Dryness Affected Bark of Hevea brasiliensis
- 2011
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Ingår i: Journal of Sustainable Forestry. - : Informa UK Limited. - 1054-9811 .- 1540-756X. ; 30:4, s. 329-342
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Tidskriftsartikel (refereegranskat)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.
(författare)
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Effect of 2,6-Dichlorobenzonitrile (DCB) on Secondary Wall Deposition and Lignification in the Stem of Hibiscus Cannabinus L.
- 2013
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Ingår i: Journal of Plant Development. - : Editura Universitatii Alexandru Ioan Cuza din Iasi. - 2065-3158. ; 20, s. 25-33
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Tidskriftsartikel (refereegranskat)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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