Changes of physiological indexes of petals during the flowering period of Nymphaea hybrid of different colors

【Objective】To explore the changes in the physiological indexes of petals in the process from flowering to senescence of Nymphaea hybrid, a precious aquatic plant of the water lily group, and to provide a theoretical basis for the regulation of the flowering period and the development and application of N. hybrid.【Method】N. hybrid plants of four different colors(purple, pink, yellow and white) were taken as the research objects. Physiological indexes such as the content of soluble sugar(SS), soluble protein(SP), starch(St) and proline(Pro), enzyme activities including peroxidase (POD), superoxide dismutase(SOD), catalase(CAT) and polyphenol oxidase(PPO), the content of malondialdehyde (MDA), cell membrane permeability and the activities of lipase(Lip) and lipoxygenase(LOX) were determined at different flowering stages of the petals, and the correlation analysis of each index was carried out. The change rules for the physiological indexes of N. hybrid of different colors were studied during the flowering period.【Result】During the flowering and senescence period, the contents of SS and SP of the four N. hybrid flowers increased first and then decreased with the flowering process, reaching a peak at the full flowering stage, and rapidly decreased to the final flowering stage, while the St showed a trend of falling first and then rising and falling again. The content of Pro in the petals decreased continuously from the initial flowering stage. The changes of enzyme activities were different:the activities of POD, SOD, CAT and PPO enzymes increased first and then decreased, the maximum activity of POD and PPO appeared at the flowering stage, and the peak activity of SOD and CAT in purple and pink N. hybrid appeared at the initial flowering stage, while the peak activity in yellow and white N. hybrid appeared at the flowering stage. The MDA content and cell membrane permeability in the petals increased continuously. Lip activity showed a decreasing, increasing and decreasing trend, while LOX activity decreased with flowering stage, reaching its minimum at the final flowering stage. The correlation analysis of the physiological indexes of N. hybrid showed that nutrients, protective enzymes and anti-stress substances had positive regulatory effects, while MDA and cell membrane permeability had negative regulatory effects.【Conclusion】The flowering and senescence of N. hybrid petals are affected by many factors. The synergistic effect of nutrients, protective enzymes and antistress substances in petals during flowering candelay the process of senescence, while the aggravation of membrane lipid peroxidationcan lead to senescence and apoptosis of petals. The yellow N. hybrid has a longer flowering period and higher ornamental value, and is worthy of further popularization and application in production and landscape settings.