Figure 2.

A, Water potentials (measured isopiestically) of individual corn roots (○) collected at different times during the day, soil surrounding the same roots (▵), and leaves (•) of the plants from which the roots were sampled. Each symbol records a measurement from one root, soil, or leaf sample. B, Osmotic potential of the contents of the xylem lumens of the same individual roots used for the measurements of water potential in A. At each sample time the osmotic potential for the sap of each root was determined in two ways: (a) by isopiestic measurements of exuded sap (•), and (b) from in situ measurements of elemental concentrations in vessel lumens of frozen pieces of the same roots by cryoanalytical microscopy (○). C, Percent embolized LMX vessels in roots collected at the same times as those in A and B. Values (○) are for the same individual roots measured in A and B (see text for details). Values (*) are means (n = 2–4) for these and other roots from the same plants frozen at the same times.