2018 ASHS Annual Conference

Water deficit stress during shipping and retailing can reduce postproduction shelf life and marketability of floriculture crops. To alleviate damage by water deficiency, plants need to limit transpirational water loss by inducing stomatal closure. Osmotic stress induces stomatal closure similar to water deficit stress in plants, and could be used as a convenient tool to enhance water deficit stress tolerance. The objective of this research was to investigate whether treatment with a high concentration of CaCl₂ could trigger a response to osmotic stress that induces stomatal closure and enhances water deficit stress tolerance in viola (Viola cornuta ‘Sorbet XP Yellow’). Leaf relative water content (RWC) and stomatal conductance were measured daily after CaCl₂ application. Preliminary studies that included various chemicals showed CaCl₂ was the most effective agent at delaying wilting under water deficit stress in viola. Compared to control, viola treated with CaCl₂ at 200 and 300 mM showed increased shelf life by 3.7 and 2.7 days, respectively. Leaf RWC of control plants was dramatically reduced 3 days after treatment and continued to decrease, while CaCl₂-treated plants maintained leaf RWC as high as that of well-watered plants until 6 days after treatment. On day 7, leaf RWC of plants treated with CaCl₂ was about twofold higher than that of control plants. Stomatal conductance was reduced by 73% to 86% within 4 hours after treatment with CaCl₂ compared to that of control plants. Our results indicated that osmotic stress induced by the treatment of high concentration of CaCl₂ might have caused stomatal closure, resulting in reduction of water loss and extension of shelf life under water deficit stress in viola. Pre-treatment of high concentration of chemicals such as fertilizers prior to shipping could enhance tolerance to water deficit stress in certain bedding plants.