| Tree peony (Paeonia suffruticosa Andr.), originating in China, belongs to the section Moutan in genus Paeonia of the Paeoniaceae famliy. It is widely used as an ornamental plant because of its large showy flowers and ornamental foliage. Little was known by human being to the mechanism of bloosming and senescence of tree peony. To deeping the acknownlage of the mechanism in florescence and flower senescence, we investigated sucrose metabolism, antioxidative activity and endogenous hormones in two tree peony (Paeonia suffruticosa) petal and its chemical regulations, which will be very useful to establish a solid theretical and practical foudation for prolonging vase life and storage period of the cut flowers. The results showed as follow:1. The results showed that total soluble sugar content was ripidly increasing in company with cell enlargement of two peony petal of florescence and flower senescence. The contents of hexose (glucose and fructose) were markedly increased in florescence period and get highest level at full-opening, whereas the content of sucrose was reduction in different developmental stages. The hexose content and sucrose degration index (SDI) were postively correlated with the fresh weight of flower. The activity for acid invertase (AI) increased in florescence and decreased after flower opening and remained at high levels during development periods. The soluble sugars metabolism rely on the 4 enzymes activities of acid invertase(AI), neutral invertase(NI), sucrose synthase(SS) and sucrose phosphate synthase (SPS), which was deduced from principal component analysis. Our results suggest that hexose accumulation might be important for florescence and flower senescence of some tree peony cultivars.2. The results showed that a ripid accmulation of MDA content lead to the continuous increase of petal cell membrance permeability during florescence and flower senescence. There were some differences of lipid peroxidation metabolisam in ’Luoyanghong’ and ’Huhong’. There was significantly positive correlation between O2- production and H2O2 and MDA content in ’Luoyanghong’, samely there was significantly positive correlation between O2- production and MDA content in ’Huhong’. O2- production has positively and significantly direct effect to MDA content, but others of main factors as H2O2, AsA-POD, CAT and PPO have different effect in two tree peony. The active oxygen turned into imbalance in lipid peroxidation during during florescence and flower senescence of two tree peony. It implied that O2- production was the key factor affecting the membrane lipid peroxidation metabolism in two tree peony during florescence and flower senescence.3. The extracts from 6 peonies petals were isolated using water and 50% ethanol. Their antioxidation activities were detected and evaluated by four systems of DPPH, O2-,·OH and PUFA with controls for Vc and BHT. Based on the generating and detecting systems of DPPH radical、hydroxyl radical (·OH)、superoxide radical (O2-) and PUFA peroxidation of yolk lipoprotein, water or 50% ethanol extracts of 6 peonies petals were investigated for the competitive abilities to active reactions. The results indicated that the water or 50% ethanol extracts from tree peonies petals could reduce light absorption of DPPH and·OH initiated hydroxylation of salicylate, and inhibit O2- mediated light chemical reduction of nitroblue tetrazolium (NBT) effectively. Both have significant inhibitions to lipid peroxidation of polyunsaturated fatty from yolk lipoprotein, in which DPPH scavenging activities of 6 peonies water extracts were higher than that of 200μg·mL-1 BHT, but lower than 80μg·mL-1 Vc. In 4 kinds of detecting systems of antioxidation, the peroxidation activity of deep colored flowers of tree peonies was higher than that of light colored flowers of tree peonies.4. There were rich with total phenolics, flavonoids and anthocyanin of petal in ’Luoyanghong’ and ’Huhong’, while the content of total phenolics decreased in petal during florescence and flower senescence of tree peonies. The antioxidative activity and secavenging ridical ability were keeping at a high level during florescence and declined ripidly after blooming. Significantly positive correlation existed between content of total phenolics and IC50 of DPPH secavenging ability in both the tree peony cultivars. It was proposed that decrease of content of poly phenolics and antioxidative activity was a main reason for petal senescence of tree peonies. Tree peonies flowers, from early bloom to full opening, were confirmed to be the optional stage in view of the nutritional consideration.5. The respiration changes in ’Luoyanghong’ and ’Huhong’ have those characterstics of a typical respiratory climacteric type in the flower opening and natural senescence in tree peonies. The peaks of respiratory climacteric were at full-opening stages and middle-opening stage, respectively. With florescence and senescence in tree peonies, the contents of endogenous IAA, ZR and GA3 decreased and the content of endogenous ABA accumulated in petal. The change pattern of ethylene production in ’Luoyanghong’ was consistent to an ethylene climacteric of cut flower, but ’Huhong’ behaved a like increase during later stage cut flower. The activities of ACO in tree peonies petal declined slowly, while ACO activity has uncorrlated to ethylene production. It suggested that the tree peonies petal senescence is caused by unbalance of endogenous hormones levels during florescence and flower senescence.6. The production of ethylene over senescent stage mainly results from receptacle, stamens and petals, whereas the most part of ethylene production in intact flowers depended on petals. Peak of ethylene production from stamen occurred at initial bloom stage. ACC content of petals decreased slowly over flowering and increased rapidly at senscent stage. ACC content of stem fell continuingly over flowering and senscence. ACC content of petiole and leaf remained virtually unchanged in flowering process. Those results indicated that the difference in ethylene and ACC content in various parts of flower played an key role in regulation of inflorescence and senscence, and difference in transporttion and distribution of ethylene and ACC was present among organs of tree peony flower.7. The vase life and the optimum ornamental period of cut tree peony flowers are relatively short when kept in distilled water (control) with the flower opening index change. The vase life could be prolonged when kept in the floral preservative, which could raise the max flower diameter and the fresh weight of flowering branches. In vase period, the water absorption and loss of flowering branches decreased continuously, and the water balance value reached the maximum at 1 day of inserting in distilled water condition. However, fresh-keeping solution could improve water status, and delay the time of hydrologic balance value from positive to 0, which showed significantly positive correlation to vase life. It is therefore proposed that the optimum harvesting period of cut tree peony flowers is from soft bud to the beginning of opening, and the floral preservative could improve the quality of cut tree peony flowers in vase-holding. |
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