Pathophysiological Investigations on Water Potential Components in Lodgepole Pine Seedlings

Abstract

For monitoring of the disease development of Armillaria root rot and bioassaying of toxic metabolites of Ceratocystis spp., changes in water potential components of lodgepole pine seedlings were determined by means of pressure-volume analysis. Comparisons were made with water-stressed seedlings. Under water stressed conditions, the wilting point (ψ^t1p_w) of the seedling decreased gradually as the time advanced until chlorosis occurred. Once chlorosis appeared, a lowering of ψ^t1p_w broke down. As to the bulk elastic modulus (ε), ε_max showed no appreciable differences to the controlled conditions before chlorosis appeared. In the case of Armillaria infection, ψ^t1p_w decreased only a little accompanied by disease development, compared with the water stressed conditions. However, ε_max increased twice than that of the control. As to bioassay of toxic metabolites, a metabolite from C. minor had direct effects upon water status of lodgepole pine seedlings. The result suggests that the loss of elasticity of the cell wall was induced by absorption of the metabolite. This technique for monitoring disease development is useful for predicting changes in the water status of the tree and studying pathogenesis of certain kinds of tree disease.