Stevenson Joshua F, Matthews Mark A, Rost Thomas L
Department of Biology and Chemistry, Texas A&M International University, 5201 University Blvd., Laredo 78041.
Department of Viticulture and Enology, One Shields Ave., University of California, Davis 95616.
Plant Dis. 2005 Jun;89(6):543-548. doi: 10.1094/PD-89-0543.
Symptoms of Pierce's disease were studied in an anatomical context from infected grapevines (Vitis species) collected from field sites within Napa Valley, CA. Two symptoms, green islands and matchsticks, are reported in this study. Green islands formed as a result of incomplete initiation of the phellogen. In regions of the stem where a phellogen and subsequent periderm arose, immediately exterior tissue was cut off, causing it to brown. In regions of the stem where no periderm is formed, the exterior tissues remained green. Consequently, the stem is mottled with both green living epidermis and brown dying epidermis as determined by the presence or absence of an underlying periderm. Matchsticks formed when the leaf lamina separated from the petiole, and the petiole remained attached to the stem. Lamina broke off from the petioles consistently in a fracture zone where xylem from the petiole anastomoses into the five major veins of the leaf. No separation layer was found to explain this pseudoabscission.
在加利福尼亚州纳帕谷田间采集的感染葡萄藤（葡萄属物种）上，从解剖学角度研究了皮尔氏病的症状。本研究报告了两种症状，即绿岛和火柴梗状。绿岛是由于周皮形成层起始不完全所致。在茎的某些区域，周皮形成层及随后的周皮产生后，紧邻的外部组织被切断，导致其变褐。在茎的未形成周皮的区域，外部组织仍保持绿色。因此，根据是否有下层周皮，茎上既有绿色的活表皮，也有褐色的死表皮，呈现斑驳状。火柴梗状症状是在叶片从叶柄分离而叶柄仍附着于茎时形成的。叶片在一个断裂区始终从叶柄脱落，在该断裂区，来自叶柄的木质部与叶片的五条主要叶脉相连。未发现有分离层来解释这种假脱落现象。
