Morphology and Anatomy of Intumescence Development on Tomato Plants1

Abstract

Abstract Plants of Lycopersicon esculentum Mill cv. Oxheart, the cultivated tomato, and L. hirsutum Humb. & Bonpl. PI LA 1625, a wild tomato, were placed in small Plexiglas boxes in a growth chamber and exposed to air from a pressurized laboratory supply line to induce intumescence injury. External symptoms of injury on the 2 species were different, but anatomical responses were similar. Injury on L. hirsutum consisted primarily of gall-like protrusions 1-2 mm in diameter on leaves, whereas symptoms on L. esculentum consisted primarily of callus-like tissue on petioles, midribs, and stems. Some injury of each type was found on both species. When severely injured, leaves wilted and abscised on L. esculentum , but not on L. hirsutum . Where injury occurred, the epidermis and underlying 2 or 3 layers of cells hypertrophied and produced intumescences. Vascular tissue of L. esculentum exhibited tyloses which occluded xylem vessels, apparently blocking water transport and causing wilting and abscission of leaves.