| Cut flower postharvest longevity is affected by many factors. This research seeks to address vase solution micro-organisms, vase solution pH, and gene expression to improve vase life. Bacterial growth in vase solutions can lead to stem vasculature blockage causing water stress symptoms that reduce postharvest quality. However, managing the species of bacteria may be more important than maintaining low microbial loads. This research isolated and identified ten bacteria species associated with cut Zinnia postharvest, including Pseudomonas fulva, Serratia ficaria, Rhizobium radiobacter, Chryseobacterium sp., Pantoea ananatis, Bacillus pumilus, Chryseobacterium daejeonense, Brevundimonas sp., Escherichia coli K 12, and Pseudomonas marginalis, and investigated the effects of pure cultures on cut Zinnia 'Benary's Giant Wine'. Stems inoculated with P. fulva and E. coli K 12 had significantly greater vase lives of 9.5 and 9.4 d, respectively compared P. marginalis, P. ananatis, R. radiobacter, and a nutrient broth control (7.0, 6.9, 6.8 d, and 7.3, respectively). The other bacteria species resulted in an intermediate vase life, which were statistically similar to each other and to the deionized water control (8.6 d). There were no significant differences in water uptake and vase solution bacteria concentrations among all treatments.;Vase solution pH is another important postharvest factor and low pH may improve stem water uptake, reduce embolization, and slow bacterial growth. In these studies we investigated the effect of solution pH (acidic, neutral, basic, and a commercial preservative) and the addition of two different bacteria strains from previous studies, one detrimental (P. marginalis) and the other beneficial (E. coli K 12), on Zinnia postharvest, including the number of days to water stress (DTWS), stem hydraulic conductivity, and bacteria counts inside and outside the stem. Non-surface sterilized stems held in solutions with only the beneficial bacteria or only preservative had the most DTWS (8.0 d). The number of bacteria inside and outside the stem were lowest in the preservative compared to the other solutions. Among the treatments with surface sterilized stems, acidic solutions had a significantly lower percent loss in conductivity (64%) when the lower 5 cm of the stem was removed, compared to the preservative (87%) and neutral (83%). These studies showed bacteria species in the vase solution have an effect on postharvest, and by combining low pH and beneficial bacteria an effective novel organic floral preservative may be possible.;Analysis of the changes in global gene expression patterns during the onset of peduncle bending (bent neck) and petal blueing in cut Rosa hybrida 'Freedom' identified 297 and 337 differentially expressed genes compared to healthy tissues. Differential expression was also performed comparing healthy neck tissues of two cultivars, 'Freedom' and 'Forever Young', the latter with a significantly longer vase life in previous studies, which identified 818 differentially expressed genes. The data suggest that bent neck may be due to cell wall degradation of the peduncle related to general senescence and petal blueing may be due to sugar deprivation. All tissues had significant expression of genes related to various stressors, including wounding, pathogens, and water deprivation. This work will provide further assistance to postharvest scientists creating novel vase solutions, breeders using marker assisted selections, and molecular geneticists transforming rose. In total, this dissertation provides valuable information about possible novel ways to extend postharvest life of significant cut flower species based on physiological and molecular data. |
