Measurement of Leaf Water Potential by the Dye Method

The dye method for measuring leaf water potential is simple, inexpensive, and suitable for both laboratory and field work. Leaves are immersed in a graded series of solutions, and the solution which neither gains nor loses water is assumed to have a water potential equal to that of the leaf. Although limited by certain inherent errors, the dye method can be used to measure relative values and changes in potential. Specific procedures are described for the successful use of the method. There are few techniques for measuring leaf water potential (Kramer, Knipling, and Miller 1966) that are truly suitable for field work. The recently described pressure chamber method appears promising for some species (Scholander et al. 1965, Boyer 1967, Waring and Cleary 1967). The dye method, also known as the Shardakov (1948) or density method, is another useful technique because it is simple and requires no elaborate or expensive equipment. The dye method has been described elsewhere, but no comprehensive discussion is readily accessible to many workers. This report examines the method and describes specific procedures and precautions that need to be taken for its successful