| Herbaceous peony (Paeonia lactiflora Pall.) is a popular cut flower in recent years, and mainly used in wedding occasions. Bending stem is an excellent ornamental trait in traditional landscape peony cultivation, which has cultural atmosphere, however, in cut flower cultivation, stem bending is not permitted. How to improve the quality of stem is the important problem should be solved urgently in the course of peony cut flower cultivation. Mechanical strength is the main technical indexes of stem quality. To understand the physiological mechanism that affects the inflorescence stem mechanical strength of herbaceous peony, dynamic clustering method was used to categorize the peony in accordance with the mechanical strength differences. Stem mechanical strength and the relationship with the stem growth indicators, the contents of mineral elements, cell wall chemical composition were analyzed, also, differentially protein expressions on different mechanical strength peony stem as well as the influence of Ca on the peony stem quality and photosynthesis were studied. And the results as follows:(1) Herbaceous peony in this study can be divided into three categories by stem mechanical strength using the method of dynamic clustering, namely high mechanical strength, medium mechanical strength and low mechanical strength class peony varieties,. Stem diameter and stem weight difference between each type of extremely significant level, flower weight up to significant level,. Correlation analysis showed that the stem mechanical strength significantly positively correlated to stem diameter and stem weight, and plant height was positively correlated flower weight of low mechanical strength cultivars was significantly negative correlated. Stem diameter as well as stem weight coefficient of variation was lower than that of plant height together with flower weight, which can better reflect the features of herbaceous peony stem mechanical strength.(2) For various types of mechanical strength, Ca, K, Mg, Cu, Zn and Si are characterized by high mechanical strength variety> medium mechanical strength variety> low mechanical strength variety, the content of Fe and Mn in contrast. Among them, Ca, K, Mg and Si content were significant differences between the type, and the others were not significant difference between the types. Correlation analysis showed that stem mechanical strength of the high mechanical strength class significantly positively correlated to Ca, K and Si contents, and the medium together with low one significantly positively correlated to Ca and Si contents. Mechanical strength positively correlated to Cu contents, and significantly associated with medium mechanical strength varieties. The correlation was different in stem mechanical strength and Mg, Fe, Mn, Zn content.(3) Contents of cellulose, lignin and pectin in the stem of ’Da Fugui’ together with ’Yangfei Chuyu’, which has high mechanical strength, were higher than that in ’Hong Yinzhen’, which has low stem mechanical strength, and soluble pectin contents on the contrary. Correlation analysis showed that stem mechanical strength significantly positively correlated to the contents of lignin and protopectin. Mechanical strength positively correlated to the contents of cellulose and soluble pectin during0to7days together with14-21days after budding, also, positively correlated to lignin contents, negatively correlated to cellulose contents and significantly negatively correlated to soluble pectin during28to35days after budding.(4) Differentially expressed proteins of inflorescence stems in two different herbaceous peony showed that more than1700clear protein spots were detected and53of which varied significantly. Moreover,23of the differentially expressed proteins were identified and confirmed by MALDI-TOF MS, involved in various biological processes such as metabolism, protein biosynthesis and transport, signal transduction. defensive response. The results also showed that inflorescence stem mechanical strength was strongly connected to cinnamyl alcohol dehydrogenase(CAD), xyloglucan endotransglucosylase/hydrolase(XTH).(5) Calcium sprays significantly increased calcium contents of inflorescence stems and the breaking force, the contents of cellulose, lignin and pectin in inflorescence stems were all significant increased, and cellulose contents reached456.54μg·-g-1, enhanced by28.5%, soluble pectin contents were significant decreased. The breaking force positively correlated to cellulose, lignin, protopectin as well as total pectin contents, and negatively correlated to soluble pectin contents. Net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr) as well as water use efficiency were all increased, Pn up to17.07μmol·m-2·s-128days after calcium applications, enhanced by29.6%, Gs, Tr and WUE enhanced by55%,20%,7.6%, respectively. Calcium sprays led to significantly increase of the maximum net photosynthetic rate(Pmax), which up to20.71μmol·m-2·s-1after calcium application, enhanced by24.6%, light saturation point (LSP) together with light compensation point (LCP) up to902.5μmol·m-2·s-1and7.27 μmol·m-2·s-1, respectively, enhanced by7.5%and decreased by34.5%。... |
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