Water relations of citrus exocortis viroid-infected grapefruit trees in the field
1998
Moreshet, S. | Cohen, S. | Assor, Z. | Bar-Joseph, M.
Citrus viroids (CVds) were used to limit citrus tree size ('dwarfing'). It is hypothesized that changes also occur in the hydraulic properties of the conducting system, thereby affecting water relations Grapefruit trees (var. Star Ruby on Troyer Citrange rootstock) in northern Israel were infected with citrus exocortis viroid (CEVd). The orchard was drip irrigated. The infected (I) and apparently healthy (H) control plots were subdivided into wet (W) and dry (D) irrigation treatments receiving 100% and 70% of the recommended irrigation quantity for the region. Soil water content, soil temperature, water uptake, leaf and stem water potential, and leaf conductance were measured in addition to climatic variables. Water uptake response to increasing springtime soil temperatures was greater in healthy than in infected trees. Leaf conductance in the infected trees was lower than the non-infected trees only in the sixth year after inoculation. Stem water potential was significantly lower in the CEVd-infected trees than in the control trees. Water uptake was lower and hydraulic resistance higher in infected than in healthy trees. It was concluded that GEVd causes a reduction in the water uptake ability of the root and canopy system. Possible mechanisms for this are discussed.
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