Résumés
Abstract
Uncommon, opaque particles (of approximately 20-22 nm, referred to as OP), aggregating into paracrystalloids occurred only next to colonized cells in carnation plants of either a susceptible or resistant cultivar (cv.) infected with Fusarium oxysporum f.sp. dianthi. In the susceptible plant, those structures occurred in vessel lumina and host walls, apparently associated with their alterations, but not in parenchyma cells, a situation which was the exact opposite of that observed in resistant plants. In comparison with apparently similar structures reported in other systems, paracrystalloids and their OPs did not seem to have exact counterparts in plants infected with viruses or fungi, although similar paracrystalloids were observed in nematode-infected plants. The OPs were associated in both cvs. with fine opaque matter, often displaying fine filamentous structures, and were in addition connected to fungal cells in the susceptible cv. Similar structures also extended through host walls into adjoining cells; these relations with parenchyma cells in resistant plants were interpreted as if the particles therein were akin to, if not exactly of the same nature as those in susceptible plants. As the opaque matter, the filamentous structures and the OPs were interrelated and associated with pathogen cells, it seemed warranted to assume that the OPs were issued from the pathogen.
Résumé
Des structures cristallines opaques formées de particules singulières (d’environ 20-22 nm en diamètre désignées OP) ont été observées uniquement dans le voisinage de cellules colonisées dans des plants d’oeillet sensibles ou résistants à l’infection par le Fusarium oxysporum f.sp. dianthi. Dans les plants sensibles, les OPs se trouvaient dans les éléments de vaisseaux et les parois cellulaires, et rattachées à l’altération de celles-ci, mais elles étaient absentes dans les cellules de parenchyme du xylème. Par contre, dans les plants résistants, les OPs ne se trouvaient que dans ces cellules. En comparaison avec des structures vraisemblablement similaires rapportées pour d’autres systèmes, les OPs et les corps cristallins semblent tout à fait différents de ceux observés dans des plantes atteintes de virus ou de champignons, mais montrent une similitude avec des corps observés dans des plants parasités par des nématodes. Les OPs ont montré un rapport évident avec de la matière opaque, souvent parsemée de structures filamenteuses dans les plants des deux cvs., et en plus avec des cellules de l’agent pathogène dans le cas du cv. sensible. Des structures semblables se trouvaient souvent dans les parois de l’hôte, reliant en quelque sorte les cellules, incluant les cellules de parenchyme dans les plants résistants; ainsi, les OPs et les corps crystallins dans ces cellules semblaient pouvoir se rattacher à ces filaments comme dans les plants sensibles. En raison de l’affinité entre la matière opaque, les structures filamenteuses et les OPs, et de chacun de ces éléments avec les cellules fongiques, il a semblé pertinent d’attribuer la genèse des particules à l’agent pathogène.
Parties annexes
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