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| 2. |
- 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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| 3. |
- Sivan, Pramod, 1984-, et al.
(författare)
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P-protein in tapping panel dryness affected trees of Hevea brasiliensis
- 2008
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Ingår i: Rubber Science. - 2454-4841. ; 21:1, s. 139-144
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Tidskriftsartikel (refereegranskat)abstract
- The structural features of P-proteins in the sieve elements of Hevea brasiliensis were studied in relation to Tapping Panel Dryness (TPD) and stimulation of affected bark with ethephon and vitex (a proprietary chemical formulation). The P-protein appears as a narrow, elongated structure in the sieve plate of healthy trees and unaffected parts of TPD affected trees whereas the TPD affected area of trees on rest for three years showed thick P-protein plugs. When the affected bark of TPD trees on rest were treated with ethylene the P-protein present in the active sieve element disappeared, while stimulation with vitex resulted in a positional change in P-protein. Callose deposition that followed in such stimulated sieve elements led to their senescence. The sieve element plugging that regulate photosynthate translocation with reference to TPD is discussed.
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| 4. |
- Sivan, Pramod, 1984-, et al.
(författare)
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Structural and dimensional changes in the cambium of tapping panel dryness affected trees of Hevea brasilensis
- 2011
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Ingår i: Phyton - Annales Rei Botanicae. - : Berger and Sohne. - 0079-2047. ; 51, s. 231-244
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Tidskriftsartikel (refereegranskat)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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| 5. |
- Thomas, Vinoth, et al.
(författare)
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Dynamic system in the sieve tubes of Hevea brasiliensis
- 2019
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Ingår i: Rubber Science. - 2454-4841. ; 32:2, s. 199-207
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Tidskriftsartikel (refereegranskat)abstract
- A chaotic and linear spatial display of movement of globular objects is reported for the first time in themyctoplasm of sieve tubes of Hevea brasiliensis where a large number of globular objects occur in a dynamicsystem.The sieve tubes recently differentiated from the phloem mother cells of the cambial zone showed anear uniform distribution of globular objects in a continuous state of motion. The objects measured anaverage diameter of 1.6μm with a density of 200 per 1000μm2 in the viscous medium. Speed of the movingparticles recorded through the video graphs was reduced to five per cent and found that these objectsdevelop spatial patterns with respect to both loci and time within the sieve tubes. At a time, the pattern ofmovement at different loci is different and are not repeating and hence across the loci the displays arechaotic. In each locus as the time proceeds, a linear pattern develops that exists for about 152 millisecondswhich are considered as a block. The pattern in a block remains stationery except at 52nd and 102nd millisecondsin which two intermittent oscillating vibrations develop. The intermittent oscillations remain for onemillisecond and are identical in display but differ from the predominant pattern of the block. There areblocks where the oscillating vibration repeats more than what is common for all the blocks and displayedin the 50th and 100th milliseconds. As the patterns are repeating intermittently in a regular manner within ablock, the motion along the block is linear. The direction of the moving objects to form the intermittentoscillations in a block gives an indication on the direction of spatial pattern to be formed in the forthcomingblock. The patterns are chaotic as far as blocks are concerned where the spatial patterns are not repeated.The timing for both linear and chaotic spatial pattern in the sieve tube is the same for more than 250subsequent patterns studied indicating that these features seem to be predetermined and specific for aplant.
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| 6. |
- Thomas, Vinoth, et al.
(författare)
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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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Ingår i: Journal of Plantation Crops. - India : Society for Plantation Crops. - 0304-5242 .- 2454-8480. ; 41:2, s. 142-150
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Tidskriftsartikel (refereegranskat)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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