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KMID : 0368419910340020137
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Journal of Plant Biology
1991 Volume.34 No. 2 p.137 ~ p.144
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Ontogeny of Haustorial Xylem in Parasitic Angiosperm Cuscuta australis R. Brown
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Lee Kyu-Bae
Lee Chai-Doo
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Abstract
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Xylogenesis of the haustoriuam in the parasitic angiosperm Cuscuta australis R. Brown grown on the host plant Trifolium repens L. was studied with light microscopy. As the first event indicating the ontogeny of the haustorial xylem, cell divisions occurred in the fascicular and interfascicular regions of the stele of the parasite stem bearing a mature upper haustoriuim, the portion of haustorium external to host organ. The smaller derivatives contained densely stained cytoplasm and prominent nuclei. It confirmed that these dense cytoplasmic derivataives resulted from the division of the previous vacuolated parenchyma cells. As the haustorium had penetrated the host tissue, the cell division activity extended acropetally from the xylem of the parasite stem toward the base of the haustorium through the interfascicular region of the parasite stem. Thus a strand of the dense cytoplasmic cells was established. At the same time, the densely stained cells adjacent to the xylem of the parasite stem began to differentiate into xylary elements. Eventaually, a strand of haustorial xylem was formed acropetally along the way of the cells with increased cytoplasmic density. The acropetal induction of the division activity of parenchyma cells and its haustorial xylogenesis in the stele of the parasite stem was discussed in relation to a possible generation of morphogenetic or hormonal signal which might lead to a specific pattern of haustorial xylogenesis.
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