EFFECTS OF CHEMICAL DRYING AGENTS ON THE FINE-STRUCTURE OF ALFALFA CUTICLES AND EPICUTICULAR WAXES

Chemical drying agents reduce the curing time of alfalfa (Medicago sat iva L.), but mechanisms have not been defined to explain this reductio n. This study was conducted to define the physical effects of drying a gents on alfalfa stem surfaces and to determine the distribution of ap plied cations on the stems. Field-grown alfalfa was treated with water and nine solutions consisting of all possible combinations of three c ations (Na+, K+, Cs+) and three anions (C2H3O2-, CO32-, OH-). Followin g treatment application, plants were air-dried under ambient condition s, stem samples excised and prepared for scanning electron microscopy (SEM) and energy dispersive x-ray microanalysis (EDXA). Epicuticular w axes were removed with chloroform on one set of samples to allow obser vation of the cuticle. All nine treatments reduced drying time relativ e to the control. Based on SEM observations, treatment with C2H3O2- co mpounds resulted in large cracks in epicuticular waxes and the cuticle , while CO32- and OH- treatments altered wax texture and caused pittin g of the cuticle. Cesium was detected on the Cs-treated samples with E DXA and its distribution was uniform over the stem surface. Drying age nts affected the physical structure of alfalfa epicuticular waxes and cuticles, but treatments that produced the most subtle physical change s caused the greatest reductions in drying times. These observations d o not support extensive wax removal, wax platelet reorientation, or in hibition of stomatal closure as mechanisms of increased drying rates.