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Cytology and Histology

Anatomic Changes Resulting from the Parasitism of Tomato by Orobanche ramosa. Barbara White Pennypacker, Research associate, Department of Plant Pathology, The Pennsylvania State University, University Park 16802; Paul E. Nelson(2), and Stephen Wilhelm(3). (2)Professor, Department of Plant Pathology, The Pennsylvania State University, University Park 16802; (3)Professor, Department of Plant Pathology, University of California, Berkeley 94720. Phytopathology 69:741-748. Accepted for publication 23 January 1979. Copyright 1979 The American Phytopathological Society. DOI: 10.1094/Phyto-69-741.

Histologic studies were conducted on roots of tomato (Lycopersicon esculentum) cultivar VF 145 parasitized by Orobanche ramosa. The point of attachment of the parasite to the host consisted of a mass of undifferentiated, polymorphic Orobanche parenchymal cells extending from the tomato epidermis to the xylem tissue. The polymorphic cells contacted the host xylem cells, occasionally penetrated them, and then differentiated into parasite xylem vessel elements. These newly differentiated parasite xylem vessels connected the host xylem to the main vascular system of the parasite. Other polymorphic cells became tightly appressed to phloem sieve cells of the host. These undifferentiated cells probably absorbed nutrients from the sieve cells via the sieve areas and transported the nutrients back to the parasite. O. ramosa established both a xylem and a phloem connection with its host.