DEHYDRATION AND MICROBIAL IMPACTS ON WATER UPTAKE AND POSTHARVEST QUALITY OF CUT LILY
Water plays a vital role in postharvest physiology of cut flowers. There are several factors affecting water uptake of cut flowers, including aspiration into the xylem and bacterial occlusion. While numerous studies have focused on water balance with cut flowers, few of them have focused on cut Lilium. After harvest, cut lilies encounter discontinuous water uptake, and the duration of exposure in air varies depending on the handling procedure. The critical duration of desiccation that would cause irreversible damage to lilies is still unknown. Furthermore, commercial lily growers have questioned the necessity of cleaning buckets to reduce bacteria and microbial building in holding solutions. In this dissertation, a variety of approaches were used to address these factors and how they affect lily postharvest quality. We investigated the effect of exposure time in air. Lilies had some rehydration ability after holding in air for 24 h, but longer exposure time reduced total water uptake and postharvest quality. The research target then shifted to microbial effects on water uptake and quality. The cumulative water absorption and flower diameter were negatively correlated to bacterial numbers in water and the exposure time in bacterial water. Bacterial concentrations of 107 cfu·mL-1 (colony forming unit per mL) caused inferior postharvest quality. The abundance of bacteria was greatest in the lower stem, especially in the lowest 15 cm. By using 16S rRNA gene sequencing, we found different flowers (rose, lily, and gerbera) affect the composition of microbial community, and the diversity of microbial communities increased over time in the vase period. In addition, bacterial taxa and chloroplast as well as mitochondria showed dynamic changes of relative abundance over time as well. We conclude the duration that cut lilies are exposed to dry, non-refrigerated conditions should be kept as short as possible. While a real financial cost, buckets should be regularly cleaned, and water replaced frequently to avoid microbial build-up. Finally, the sequencing work revealed the complexity and dynamics of the microbiome in a cut flower vase and highlights the limited information of vase microbiology the industry currently has.
16S rRNA gene sequencing; colony-forming-unit; cut flowers; postharvest physiology; xylem occlusion
Gandolfo Nixon, Maria Alejandra; Setter, Tim; Winans, Steve; Chang, Yao-Chien
Ph. D., Horticulture
Doctor of Philosophy
dissertation or thesis