Benzyladenine and Gibberellic Acid Application Prevents Abscisic Acid-induced Leaf Chlorosis in Pansy and Viola

Abstract

Drought stress during the shipping and retailing of floriculture crops can reduce postproduction shelf life and marketability. The plant hormone abscisic acid (ABA) mediates drought stress responses by closing stomata and reducing water loss. Applications of exogenous s-ABA effectively reduce water loss and allow a variety of species to survive temporary periods of drought stress. Unfortunately, s-ABA application can also lead to leaf chlorosis, which reduces the overall quality of economically important bedding plant species, including Viola ×wittrockiana (pansy). The goal of this research was to determine how to prevent s-ABA-induced leaf chlorosis in pansy and a closely related species, Viola cornuta (viola). All concentrations of both spray (250 or 500 mg·L−1) and drench (125 or 250 mg·L−1) s-ABA applications induced leaf yellowing. Young plants at the plug stage and 11-cm finished plants with one to two open flowers were further evaluated to determine if the developmental stage of the plants influenced s-ABA effectiveness or the development of negative side effects. Both plugs and finished pansies and violas developed leaf chlorosis after s-ABA applications, but symptoms were generally more severe in finished plants. The individual application of benzyladenine (BA), gibberellic acid (GA4+7), or the ethylene perception inhibitor, 1-methylcyclopropene, before s-ABA application had no effect on the development of s-ABA-induced leaf chlorosis. However, applications of 5 or 10 mg·L−1 BA and GA4+7 as a mixture (BA + GA4+7) before a drench or spray application of s-ABA prevented leaf chlorosis. The application of s-ABA and BA + GA4+7 would allow floriculture crops to tolerate temporary periods of drought stress without any loss of postproduction quality.