|Panciera, M - UNIV OF ALASKA|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 22, 1997
Publication Date: N/A
Interpretive Summary: Effective methods are needed to quickly harvest forage crops. Curing time is reduced when various chemicals are applied after cutting alfalfa. Until the current study, little was known about the effects such chemicals produced on alfalfa stem surfaces. Sodium, potassium and cesium cations as well as carbonate, acetate and hydroxyl anions were applied in all possible combinations as aqueous solutions. Stems were air-dried under field conditions and prepared for observation with a scanning electron microscope, an instrument that highly magnifies plant surfaces. Simultaneously, non-destructive chemical analysis was performed with an energy dispersive x-ray analyzer(EDXA) to determine locations of exogenous chemicals. Acetate compounds induced significant surface cracks and other treatments caused surface pits. Cesium was evenly dispersed over the plant surfaces as detected with EDXA. Our observations did not uphold the theory that changes in surface wax configuration, the absence of wax nor alteration of stomatal conditions affect alfalfa curing time.
Technical Abstract: Chemical drying agents reduce the curing time of alfalfa (Medicago sativa L.), but mechanisms have not been defined to explain this reduction. This study was conducted to define the physical effects of drying agents on alfalfa stem surfaces and to determine the distribution of applied cations on the stems. Field grown alfalfa was treated with water and nine solutions consisting of all possible combinations of three cations (Na+, K+, s+) and three anions (C2H3O2-, CO3=, OH-). Following treatment application, plants were air-dried under ambient conditions, stem samples excised and prepared for scanning electron microscopy (SEM) and energy dispersive x-ray microanalysis (EDXA). Epicuticular waxes were removed with chloroform on one set of samples to allow observation of the cuticle. All nine treatments reduced drying time relative to the control. Based on SEM observations, treatment with C2H3O2- compounds resulted in large cracks in epicuticular waxes and the cuticle, while CO3= and OH- treatments altered wax texture and caused pitting of the cuticle. Cesium was detected on the Cs-treated samples using EDXA and its distribution was uniform over the plant surface. Drying agents affected the physical structure of alfalfa epicuticular waxes and cuticles, but the extent of these effects did not parallel reductions in drying times. These observations do not support wax removal, wax platelet reorientation or stomatal closure as mechanisms of increased drying time.