Flowering stage and daytime affect scent emission of malus ioensis "prairie rose"

Abstract

Flowering crabapple is an important ornamental flower. It is vital to understand the floral scent properties and the associated release dynamics for carrying out fragrant flower breeding or floral regulation of crabapple. Static headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry was used to detect the volatile compounds inMalus ioensis "Prairie Rose" flowers at different flowering stages and at different day-night time. The results showed thatmethylheptenone, phenylethanol, geranylacetone, 2-(4-methoxyphenyl)ethanol, α-cedrene were themajor compounds inM. ioensis "Prairie Rose", but the compounds released during different stages and different day-night time were significantly different (P < 0.0001). A total of 25 volatile compounds were identified from the four flowering stages. The floral scents in the initial and flowering stages were the most similar (dissimilarity 0.21). The main compounds in these two stages were geranylacetone and methylheptenone, and the contents of geranylacetone and phenylethanol were positively correlated with the flowering stages. From the bud stage to the end of flowering, the total amount of volatile compounds released showed an initial increase followed by a decrease and the amounts of compounds released during the initial flowering stage were the highest. The aliphatic and benzenoids content was significant higher in the daytime than at night. A total of 15 compounds were detected in the five time periods. Methylheptenone and phenylethanol were particularly released in the 10:00-12:00 and 15:00-17:00 time periods. There were only three common compounds among the five time periods and the types of flower volatiles released during the daytimewere obviously higher than those released at night. Fromthe nocturnal to diurnal, the amount of flower volatiles released first increased, then decreased, and the release reached a peak between 10 amand 12 noon, which was consistent with the pollination biological characteristics ofMalus flowers. Our findings are important for understanding themechanismof insect visits to crabapple and the regulation of crabapple flower scent.