Studies On Physiological And Biochemical Characteristics Of Cut Freesia During Vase Holding

Freesia hybrida, perennial herbaceous flowers, belongs to Iridaceae.It is popular with consumers because of the diversity of design and color,fragrance charming and the characteristics of wide application. Cut Freesiais one kind of the world’s top ten fresh cut flowers. Over the years, a seriesof questions of how to extend the life of cut flowers after departion fromorigion plants, prolong the turnover period and ornamental value havealways been the focus of researchers. Since the1980s, garden hybrids ofFreesia have had been introduced in China. In recent years, regularprogress has had been made in the cut flower production and applied basicresearch, and, certain accumulation in the research and practice ofcultivating new varieties. Freesia is of very high ornamental value,however, in practice applications, it existed the phenomena of theflowering concentration and short flowering time. After harvest of cutFreesia, ageing process speeds up, and its prone to flowers wilting, petalspale and so on, influences the ornamental life. So studying thephysiological and biochemical characteristics of cut Freesia during vaseholding is of positive meaning in field of how to extend the vase life andfresh-keeping in postharvest.At present, a large number of research have been made about ballbreeding, tissue culture, cultivation of curing in Freesia, However, littlewas known by human beings to the physiological and biochemicalmechanism of bloming and senescencen of Freesia. Cut flowers of Freesiahybrid ‘Shangnong Jinhuanghou’were used as material, being immersed indistilled water and6%glucose solution, respectively, to study the ways of water metabolism, changes in endogenous substance, the active oxygenbalance and endogenous hormone changes in florescence and flowersenescence, to analyse the physiological and biochemical characteristics ofcut Freesia during vase holding, and to discuss the effect of exogenoussugars on the aging of cut flowers, which provide a solid theretical andpractical foundation for proloning vase life of cut Freesia.The main results showed as follows:1. During the vase holding of cut Freesia flowers, the vase life of awhole inflorescence was about10d, while an individual floret less thanone week. Water absorption content in petals changed obviously in theprocess of vase holding, with a decrease in the early stage and picking upafter7d. During vase holding, embeded substances have obviously takenplace. Soluble protein content in petals showed a gradual decline in thevasing process.Starch content in petals of florets in different positions fellsharply after2d. Proline content in petals showed higher at the early stageof bloming than fell in the late.2. Active oxygen balance in petals of Freesia changes obviouslyduring the vase holding. Superoxide dismutase (SOD) and catalase (CAT)activities had a consistent trend, both showing a downward trend afterrising first during the vase holding. However, peroxidase (POD) activitypresented a constant increase trend. Meanwhile, a significant difference inPOD activity was observed at different position of Freesia inflorescence)the highest activity presented in base floret and the lowest activity in upperfloret).The content of Malondialdehyde (MDA) accumulated graduallyduring vase holding, and the higher MDA content was observed in basefloret than that in middle floret and upper floret at the same vase time,respectively. The content of super oxygen free radicals (O2·–) increasedobviously at2d followed by a drop at4d, and then increased up to theend of vase holding. Ability of free oxygen scavenger failed，free radicalbalance was broken, cell damage increased and the cells growed oldgradually. The results revealed that the decreased activity of antioxidant enzymes, the accumulation of O2·–and the rising of membrane lipidperoxidation level were considered to be the main causes of senescence ofcut Freesia flowers.3. Content changes of five endogenous hormones in petals wereobserved during vase holding. The contents of endogenous zeatinnucleoside (ZR) decreased constantly, and the lowest content was observedat10d, decreased by83.78%compared to that at0d. The change trend ofendogenous gibberellic acid (GA) is similar to ZR content, the lowestcontent of GA was present at10d, correspond to3.79%by compared withthat at0d. However, the content of endogenous abscisic acid (ABA),accumulating after a descend, dropped to the lowest level at4d, equivalentto52.40%of the content at0d. Endogenous auxin (IAA) content, showinga trend of decline after rising first, emerged a peak at2d, and down to aminimum level at10d, equivalent to12.17%of the highest. At the samevase period, contents of the endogenous IAA, ZR and ABA had nosignificant difference in the different positions of inflorescence, butendogenous GA content in the upper floret of inflorescence is significantlyhigher than the base and mid in the first4days during vase holding.Change of ethylene releasing rate increased followed a constant decreaseup to the end of vase holding. However, the ethylene releasing peak of midposition floret appeared at2d, while the upper floret at4d. The change ofendogenous hormone levels and the metabolic unbalance might beimportant factors of senescence in Freesia petals.