VIEW ARTICLE

Biochemistry and Cell Biology

Alterations in Growth and Water-Transport Processes in Fusiform Rust Galls of Pine, Determined by Magnetic Resonance Microscopy. Janet S. MacFall, School of the Environment, Duke University, Durham, NC 27706; Paula Spaine(2), Robert Doudrick(3), and G. A. Johnson(4). (2)USDA Forest Service, 320 Green St., Athens, GA 30602; (3)USDA Forest Service, So. For. Exp. Stn., Gulfport, MS 39505; (4)Department of Radiology, Duke University Medical Center, Durham, NC 27706. Phytopathology 84:288-293. Accepted for publication 7 December 1993. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/Phyto-84-288.

Galls on 10-mo- to 2-yr-old slash and loblolly pine seedlings inoculated with Cronartium quercuum f. sp. fusiforme were compared with healthy stems by magnetic resonance microscopy (MRM). After transpiration, high-resolution images (35–58 µm) of excised stem segments were acquired. MRM images showed a greater signal in the xylem of healthy stems than in galls, suggesting differing wood/water interactions. In 10-mo-old galled seedlings, the cambium and phloem were contiguous between healthy and galled regions. Water-transport disruption occurred in the xylem at the interface between galled and healthy regions, but in the center of the galls, secondary xylem appeared water-filled. At 2 yr of age, water transport was observed throughout the secondary xylem of a healthy stem but was completely impeded through the gall of a declining seedling. In contrast, a bright ring of conductive secondary xylem surrounded a dark, nonconductive center in the gall of a vigorous, 2-yr-old seedling. This study shows changes in anatomy and functional physiology in vivo with respect to water relations in fusiform rust galls on pine that are detectable by MRM.