Latex is the cell sap contained in secretory structures called laticifers and can be obtained by incision of laticifers. It is principally constituted by particles in suspension in a liquid matrix. Cytological studies permit two classes of laticifers to be distinguished: articulated laticifers and non-articulated laticifers. Non-articulated laticifers develop from a single cell which elongates with the growth of the plant. Articulated laticifers arise from aligned set of cells whose end walls can be degraded, transforming the cell rows into vessels. The contents of latex, especially that of Hevea brasiliensis, have been object of extensive biochemical studies focused on enzymes implicated in rubber synthesis and in stability of lutoids, stability being necessary to avoid coagulation of rubber particles, which would imply the cessation of latex flow. The role of latex in plants is unknown, although several hypothesis have been presented. It has been possible to thoroughly study the enzyme content of various latexes from articulated and non-articulated laticifers (Lactuca sativa, Carica papya and Asclepias curassavica): a high level of glycosidases activities was noted. In addition, all latexes tested possess a strong antifungal action due to enzymes. Ultrastructural studies have shown that all latexes tested induce a degradation of the fungal cell wall that may explain the fungistatic effect. The implication of latex glucosidases in the cell wall degradation process is more than likely. It has been shown that there is a synergistic effect between latex and synthetic antifungal agents, as the parietal degradation induced by latex facilitates the entrance of these synthetic agents into yeasts. These results seem to indicate that latex in situ plays a role of defense against phytopathogens microorganisms from fungal type.
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