Laticifer wound plugging in Hevea brasiliensis: the role of a protein-network with rubber particle aggregations in stopping latex flow and protecting wounded laticifers.

Tan H.Y., . and Wu J.L., . and Hao B.Z., . and Meng C.X., . and Gao Z.Q., . Laticifer wound plugging in Hevea brasiliensis: the role of a protein-network with rubber particle aggregations in stopping latex flow and protecting wounded laticifers. pp. 281-299. ISSN 1511-1768

Laticifer wounds were investigated at both the tapping cuts of tapped trees and the bark wounds specially made for investigation. Using light microscopy a protein-network was found that gradually formed within and over the laticifer wounds as latex flowed. Correspondingly a network of electron-dense material was observed under electron microscopy. The network with rubber particle aggregations in its meshes plugged the laticifer wound when latex flow stopped.The rubber particles of the aggregations retained their intact membrane and did not coagulate until some time after latex flow stopped. Therefore laticifer wound plugging might not be attributable to the coagulation of the rubber particles but to the formation of a protein-network with rubber particle aggregations. During the course of latex flow after tapping the activities of chitinase -1 3-glucanase which are known to be the important components among many defense proteins in lutoids were reduced in expelled latex and increased in the tissue of wounded bark. Thisindicated that the two enzymes and perhaps the other defense proteins in lutoids might be accumulated within and over the laticifer wounds and involved in the composition of the protein-network. Hence the protein-network might function as a biochemical barrier to prevent harmful materials from invading the wounded laticifers. The protective function of the protein-network was demonstrated by experiments in which puncturing and pathogen inoculation were made under the tapping cut and two types of laticifer wound plugs were produced: the normal wound plugs with protein-network and the wound plugs without protein-network formed by in situ latex coagulation. Under the influence of latex flow the plugs without a protein-network extended considerably while the normal plugs with protein-network did not. It is consequently suggested that the extension of the laticifer wound plugs without a protein-network might be an essential factor resulting in the onset of the laticifer disease tapping panel dryness.

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Abstract

Laticifer wounds were investigated at both the tapping cuts of tapped trees and the bark wounds specially made for investigation. Using light microscopy a protein-network was found that gradually formed within and over the laticifer wounds as latex flowed. Correspondingly a network of electron-dense material was observed under electron microscopy. The network with rubber particle aggregations in its meshes plugged the laticifer wound when latex flow stopped.The rubber particles of the aggregations retained their intact membrane and did not coagulate until some time after latex flow stopped. Therefore laticifer wound plugging might not be attributable to the coagulation of the rubber particles but to the formation of a protein-network with rubber particle aggregations. During the course of latex flow after tapping the activities of chitinase -1 3-glucanase which are known to be the important components among many defense proteins in lutoids were reduced in expelled latex and increased in the tissue of wounded bark. Thisindicated that the two enzymes and perhaps the other defense proteins in lutoids might be accumulated within and over the laticifer wounds and involved in the composition of the protein-network. Hence the protein-network might function as a biochemical barrier to prevent harmful materials from invading the wounded laticifers. The protective function of the protein-network was demonstrated by experiments in which puncturing and pathogen inoculation were made under the tapping cut and two types of laticifer wound plugs were produced: the normal wound plugs with protein-network and the wound plugs without protein-network formed by in situ latex coagulation. Under the influence of latex flow the plugs without a protein-network extended considerably while the normal plugs with protein-network did not. It is consequently suggested that the extension of the laticifer wound plugs without a protein-network might be an essential factor resulting in the onset of the laticifer disease tapping panel dryness.

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Item Type:	Article
AGROVOC Term:	Hevea brasiliensis
AGROVOC Term:	Proteins
AGROVOC Term:	Particle size
AGROVOC Term:	Latex
AGROVOC Term:	Electron microscopy
Depositing User:	Ms. Suzila Mohamad Kasim
Last Modified:	24 Apr 2025 06:28
URI:	http://webagris.upm.edu.my/id/eprint/23142

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