ELECTROLYTE LEAKAGE AND EVOLUTION OF ETHYLENE AND ETHANE FROM PEPPER LEAF-DISKS FOLLOWING TEMPERATURE STRESS AND FATTY-ACID INFILTRATION

Electrolyte leakage (EL) and ethane : ethylene ratio (EER) responses of pepper (Capsicum annuum L. 'Early Calwonder') leaf disks to temperature stresses were in close agreement. Midpoints of sigmoidal response curves following freezing stress were -4.6 and -4.4C for EL and EER, respectively, and 49.0 and 48.7C following high-temperature stress. Leaf disks exposed to temperatures below - 4C in freezing experiments were induced to while disks held at -4C and higher avoided freezing by supercooling. Evolution of ethane and EL were measured from disks infiltrated with a saturation series of 18-C fatty acids ranging from 0 to 3 double bonds. Only cis-9,12,l5 linolenic acid (18:3 n-3) stimulated ethane production and EL. In a second fatty acid experiment with 18- and 20-C acids with a double bond 3 (n-3) or 6 (n-6) carbons from the nonpolar end of the molecule, n-3 fatty acids stimulated more ethane than n-6 acids with the same number of carbons. Trienoic 18-C fatty adds stimulated more ethane than trienoic 20-C acids. Both 18-C trienoic acids yielded significantly greater EL, while values from 20-C fatty adds were only slightly higher than those of controls. Propyl gallate, a free radical scavenger, reduced ethane production without decreasing EL or K+ leakage.