Study On The Physiological Role Of ABA, H₂O₂and Ethylene During The Aging Process Of Peony Cut Flower

Peony（Paeonia lactiflora ‘Dafugui’） cut flowers at open-top stage （stage II） weretaken as objects of study. They were divided into two groups, one pretreated by0.1mMPD98059（MAPK specific inhibitor） for12h, another one pretreated by ditilled water.Each groups were divided into four equal groups and randomly put in distilled water,0.1mM ABA,10mM H₂O₂and1mM CEPA respectively for analysing themorphological of flower braches and physiological and biochemical indexes duringvasing. To study physiological mechanisms of cut peony flowers senescence, andanalyse the physiological effect of ABA, H₂O₂, ethylene and MAPK signaling passwayon the aging process of peony cut flower. The main results were as follows:1. While ethylene showed strongest effects and H₂O₂had weaker effects,exogenous ABA, H₂O₂and ethylene treatment could accelerate bloom and senescenceof ‘Dafugui’ cut flowers, accelerated moisture balance reaching zero value, increasedthe maximum flower diameter, reduced ornamental quality and increased respirationrate and ethylene release rate. In addition, apparent emergence of respiratory andethylene climacteric after these treatments indicated ‘Dafugui’ is a respirationclimacteric and ethylene-sensitive cultivar.2. On the contrary, pretreatment by PD98059decelerated respiration rate andethylene releasing rate, decreased ACS and ACO activity, ABA and H₂O₂content werealso decreased, it extend best viewing period, delayed water balance value to reach zero.In particularly,12h pretreatment decelerated respiratory and ethylene releasing rate by11.02%and15.42%respectively. Therefore, MAPK maybe play an important positiverole in the pathway of ethylene, ABA or H₂O₂regulated cut peony flowers senescence.3. ABA, H₂O₂and ethylene treatment reduced soluble protein content，increasedplasm-membrane permeability and MDA content. Considering MDA content increasewas prior to plasm-membrane permeability change, membrane lipid peroxidationproduce MDA could accelerate the oxidative damage of cell membrane and destroy cellmembrane structure.These data further suggested aggravation membrane lipid peroxidation caused cell membrane damage is the major trigger for senescence of cutpeony flowers. Just because of this, pretreatment by PD98059inhibited membrane lipidperoxidation at the early stage of vase holding and then delayed senescence of cut peonyflowers.4. The relationship among H₂O₂, ABA, ethylene and MAPK could be summarizedas follows: ABA-induced H₂O₂could activated MAPK, and activated MAPK regulatessignal transduction in two ways, one inducing ethylene releasing, the other onepromoting H₂O₂accumulation, thus activating its own activity. The ethylene producedfeedback simultaneously to regulate promoting the generation of ABA and H₂O₂.However, H₂O₂could act as intermediates of ABA and ethylene, and only regulate thesynthesis of ethylene on one way, couldn’t regulate reversely the synthesis of ABA.5. Peony （‘Dafugui’） cut flowers vased with distilled water were taken as objects ofstudy. Semi-quantitative RT-PCR analysis was used, with reference gene Actin, toanalyze ACO and ACS gene daily expression. The results showed this two geneexpressed in the whole blossom and aging period with lower leves at active period andincreasing levels at pausing period.