Water Uptake Patterns in Blighted Citrus Trees1

Abstract

Sweet orange cultivars, Citrus sinensis (L.) Osbeck, in several stages of blight (young tree decline) were studied for characteristics of waterflow or uptake. Many small and major roots and the trunk on moderately blighted trees had restricted waterflow or uptake capabilities. Some small and major roots on the blighted side of early-stage or sectored trees also had restricted waterflow or uptake capabilities, but the healthy side roots functioned similarly to those on healthy trees. Dye uptake patterns confirmed that the waterflow or uptake was restricted in the diseased portions of the trees. On moderately blighted trees, young xylem appeared to be more functional for water movement than older xylem. Necrotic roots were found on the blighted side of early-stage sectored trees and moderately blighted trees, but not on the healthy side of sectored trees or on healthy trees. The sectoring type of early blight expression affords a model system for study whereby both blighted and apparently healthy tissues occur on the same tree.