Studies On Phenolics Oxidative Metabolism In Stems Of Some Cut Flowers And Its Postharvest Regulation

Phenolic compounds, the aromatic derivatives of benzene series and related organic groups, are broadly distributed in the plant kingdom and are the most abundant secondary metabolites found in plants. Previous researches had already indicated that the phenolic metabolism in wounds and the adjacent tissues would be obviously induced by wounding. Cut flowers, very important ornamental products in the domestic and international flower market, are severely wounded in the stem-ends when cut. However, so far there is little study on the phenolics metabolism, especially the phenolics oxidative metabolism in cut flowers. Thus, this thesis focused on the main characteristics of the phenolics oxidative metabolism in stem-ends of several mainstreaming cut-flowers, and also on the effects of its postharvest regulation on the water metabolism and ornamental quality of cut roses(Rosa hybrid ‘Movie Star’). The major research results and conclusions were high-lighted below:1. Increasing browning was observed in wounds and the adjacent tissues of stem-ends in cut roses ‘Movie Star’, lilies(Lilium hybrid ‘Robina’ and ‘Manissa’) and Lilium longiflorum, during their vase life and simulated storage period. Meanwhile, an accumulation of brown substance was observed, which invaded in the vascular system in the stem-ends of the cut flowers.2. On the basis of the conventional methods, by adding 5 mmol/L Cu2+ in PPO reaction solution and adjusting its p H value to 5.7, and reducing the concentration of H2O2 to 0.01% in POD reaction solution,the determination systems respectively for the activities of PPO and POD in stem-ends of cut flowers were established, and a series of experiments demonstrated their validity and good repeatability. By using of the modified determination methods, the activities of PPO and POD in stem-ends of several cut flowers including cut roses ‘Movie Star’, lilies ‘Robina’ and carnations ‘Master’, which showed that the activity of POD in stem-ends of cut roses was much higher than those of the other two cut flowers. Further investigation indicated that the changes in activities of PPO and POD in stem-ends of cut roses, lilies or carnations during their vase life and simulated storage period were generally similar, namely both PPO and POD were at relatively low activity level within the early 12 h of the vase life or simulated storage period, thereafter both increased quickly and then decreased since the time point of 48 h or 72 h.3. The contents of total phenols in stem-ends of cut roses ‘Movie star’, lilies ‘Robina’ and carnations ‘Master’ were determined using the Folin–Ciocalteu method. The results showed that the content of total phenols in stem-ends of cut roses was significantly higher than those of cut lilies and carnations, and for cut lilies and carnations there was no significant difference in the contents of total phenols in their stem-ends. Additionally, the changes in the content of total phenols in stem-ends of the 3 cut flowers were different,for cut roses it increased within the early 72 h of vase life, while for cut lilies and carnations it firstly decreased, then increased and finally deceased again, though the time points of the lowest and highest values were different between cut lilies and cut carnations. However,the changes in the content of total phenols in stem-ends of cut roses or carnations were roughly similar during their vase life and simulated storage period.4. Combinding HPLC-DAD, LC-ESI-MS/MS and HRMS analysis, the phenolics components in stem-ends of cut roses ‘Movie star’, lilies ‘Robina’ and carnations ‘Master’ were priliminarily determined. The results show that:(1) The phenolics composition varied a lot in the stem-ends of the 3 cut flowers. For cut roses they were mainly phenolic acids, tannins and flavonoids, for cut lilies they were mainly phenolic acids and flavonoids, while for the cut carnations the species of phenolics were relatively less;(2) Ellagic acid, tiliroside and quercetin were identified in the stem-ends of cut roses. In addition, most of the phenolics in rose stem-ends contained the hexahydroxydiphenoyl group(HHDP)(300.9990 Da), indicating HHDP as the construction unit of phenolics in rose stem-ends;(3) During the vase life, the changes rules of the main phenolics contents in the stem-ends varied among the 3 cut flowers. For cut roses they are basically similar to the change rules of total phenols content, for cut lilies most of the phenolics components showed a general trend of decrease, and for cut carnations some components were generally declined, while the others were generally increased;(4) During the simulated storage period(0~48 h), the changes rules of the main phenolics components were inconsistant with the total phenolics in stem-ends of cut roses, some phenolics rise constantly, but some showed a trend from rise to decline. The changes in the contents of most phenolics and total phenols in stem-ends of cut carnations were similar in the rough during simulated storage period, i.e. they all show a downward trend.5. The effects of postharvest treatments with 4 selected inhibitors specific for polyphenol oxidase(PPO) and peroxidase(POD), two key enzymes in phenolics oxidative metabolism, on the vase life, ornamental quality and the indexes of water metabolism of cut roses ‘Movie Star’ were investigated, which showed that vase solution treatment with appropriate concentrations of POD inhibitors(p-benzenediol and o-benzenediol) and PPO inhibitors(sodium metabisulfite and sodium bisulfite) could significantly prolong the longevity of cut roses and effectively keep their ornamental quality, and also promote water uptake, enhance water balance value and maintain the fresh weight, in different extent. Further research indicated that vase treatment with suitable concentrations of p-benzenediol can significantly alleviate the physiologcal stem-blockage in stem ends of cut roses during the vase period, thus delay the decline of hydraulic conductance.