Physiological Effects Of Nano-silver On The Vase Life In Cut Flower Paeonia Lactiflora Pall

As a Chinese traditional flower, herbaceous peony (Paeonia lactiflora Pall.) is a good material for cut flowers because of its bright color, elegant type and fragrance. It is widely popular at home and abroad in recent years, especially used in weddings and other festive occasions with a broad market prospect. However, due to the short flowering of herbaceous peony together with the susceptibility to microbial infection of its stem end, a large number of pathogen always causes the blocking of stem catheter, which leads the shorten life of cut flowers. This significantly affects the ornamental quality and limits the development of herbaceous peony cut flowers in a certain extent. Therefore, finding a way to delay the senescence of herbaceous peony cut flowers is the key issue to affect the herbaceous peony flower industry. Based on the previous research, herbaceous peony cultivar ’Hongyanzhenghui’was selected as the material of this study, pulse treatment was performed on herbaceous peony cut flowers using NS as the pretreatment liquid, and its effect on the vase life and flower quality was observed; based on these, the physiological indexes and the protective enzyme activity were measured, the structure of stem bottom of herbaceous peony cut flowers was observed, the pathogenic bacteria of herbaceous peony cut flowers was identified, the AQPs was isolated and its expression pattern was detected. The main results were as follows:(1) NS treatment not only let herbaceous peony cut flowers open in advance, but also prolonged their vase life with 4 days. Meanwhile, the fresh weight and diameter of cut flower were also increased comparing with the control. In addition, under the treatment of NS, the content of soluble protein and the activity of three protective enzyme (SOD, CAT and APX) were increased, but the relative conductance, the content of malonaldehyde (MDA), superoxide anion (O-), hydrogen peroxide (H2O2) and free proline (Pro) were all decreased.(2) NS treatment improved the water uptake and the content of Ag+ of the vase cut flowers. And the content of Ag+ was the highest in the bottom of stem, followed by the leaf and the top of stem, and the lowest in the petal; and their content were all decreased with the passage of vase time. Through the observation of Scanning Electron Microscopy, the stem bottom of cut flower was covered by a large amount of microbial metabolite or hypha in the control, which reduced the transport of water and Ag+. After the isolation, purification, and identification, the dominant pathogens were determined as Phoma sp. and Alternaria sp. And it indicated that NS could significantly inhibit the growth of these two dominant pathogens.(3) Taken the RNA extracted from the petals as a template, the primers were designed according to the related genes sequence of other plants in Genbank, four AQPs genes of herbaceous peony petals were cloned including PIPIP1-2, PIPIP2-1, PIPIP2-2 and PlNIP. The full length of sequences were 651bp,1119bp,337bp and 845bp, which encoded 148,281, 75 and 230 amino acids, respectively. Homology analysis showed that the gene sequences and their encoded amino acids sequences all shared high similarities with those from other plants. And the gene accession numbers were KX235309, KX235310, KX235311 and KX235312, respectively.(4) The expression levels of four genes including PIPIP1-2, PIPIP2-1, PIP1P2-2 and PINIP in the herbaceous peony petals during different vase stages were analyzed by qRT-PCR technology. The results suggested that the four genes could all be detected in the petals, but their expression levels were differed. In total, the expression of PIPIP1-2 increased with the open process at the early flowering stage, and then decreased after the full flowering; the expressions of PIPIP2-1 and PIPIP2-2 were up-regulated during the whole vase period; but the expression change of PINIP was not obvious compared with the other three genes. In the NS treatment group, the expression levels of PIPIP1-2 were all higher than the control, but these of PIPIP2-1, PIPIP2-2 and PINIP were lower.