Abstract:

Using Oncidium flexuosum‘Honey Angle'and‘Million Dollar'cut flowers as test material and the reasons for the senescence ofO. flexuosum flowers caused by the anther cap shedding was investigated. The results revealed that the anther cap shedding of‘Honey Angle'and‘Million Dollar'resulting in petal dehydration and shrinkage earlier than the control for two days and three days,and began to release endogenous ethylene after 16 hours. The endogenous ethylene contents of‘Honey Angle'and ‘Million Dollar'increased 55.42 times and 8.57 time respectively compared to the control. After the fall of the anther cap,‘Honey Angle'and‘Million Dollar'reached their peak of endogenous ethylene contents on the 3rd and 6th day,the ethylene contents were 351.59 and 82.57 nL · g^-1 · h ^-1,respectively. Scanning electron microscope showed that there was no block flat structure on the junction between the anther cap and stamen of‘Honey Angel',whilst on the‘Million Dollar'matching block flat structure was present which may reduce abscission of the anther cap. Moreover,exogenous ethylene treatment accelerates petal senescence of‘Honey Angle'and‘Million Dollar'. Petal dehydration and shrinkage appear on the 3rd and 4th days after treatment in both varieties,respectively. Furthermore,the water content of both varieties significantly decreased by 12.57% and 20.48%,respectively,while the malonaldehyde contents significantly increased. The petal water content of‘Honey Angle'without exogenous ethylene treatment for one day is about 34.61%-43.39% of‘Million Dollar'. The results indicate that petal water content is one of the main factors of the senescence ofO. flexuosum cut flower.

Key words: Oncidium flexuosum, cut flower, ethylene, anther cap, senescence