XVI International Botanical Congess
Examples are shown of new dimensions of plant physiological anatomy made possible by improvements in cryo-analytical SEM techniques. For the first time it is possible to determine with confidence solute concentrations in vacuoles of individual cells throughout tissues and organs, to distinguish and measure gas- and liquid-filled spaces, to measure the extent and density of expanded gels, and to preserve shapes and dimensions of hydrated tissues as they were in the functioning plant. New observations have forced reevaluation of some traditional paradigms, eg. that xylem vessels do not embolize in well-watered plants, and that root pressure is driven by a high concentration of solutes in xylem sap. Cryo-SEM also makes possible faithful preservation of fragile and recalcitrant tissues that distort and collapse with conventional preparative procedures.