Comparative Study of the Petal Structure and Fragrance Components of the Nymphaea hybrid, a Precious Water Lily.

Qi Zhou,Huihui Zhang,Man Shi,Zunling Zhu

doi:10.3390/molecules27020408

Abstract

Nymphaea hybrid, a precious water lily, is a widely-cultivated aquatic flower with high ornamental, economic, medicinal, and ecological value; it blooms recurrently and emits a strong fragrance. In the present study, in order to understand the volatile components of N. hybrid and its relationship with petals structure characteristics, the morphologies and anatomical structures of the flower petals of N. hybrid were investigated, and volatile compounds emitted from the petals were identified. Scanning and transmission electron microscopy were used to describe petal structures, and the volatile constituents were collected using headspace solid-phase microextraction (HS-SPME) fibers and analyzed using gas chromatography coupled with mass spectrometry (GC-MS). The results indicated that the density and degree of protrusion and the number of plastids and osmiophilic matrix granules in the petals play key roles in emitting the fragrance. There were distinct differences in the components and relative contents of volatile compounds among the different strains of N. hybrid. In total, 29, 34, 39, and 43 volatile compounds were detected in the cut flower petals of the blue-purple type (Nh-1), pink type (Nh-2), yellow type (Nh-3) and white type (Nh-4) of N. hybrid at the flowering stage, with total relative contents of 96.78%, 97.64%, 98.56%, and 96.15%, respectively. Analyses of these volatile components indicated that alkenes, alcohols, and alkanes were the three major types of volatile components in the flower petals of N. hybrid. The predominant volatile compounds were benzyl alcohol, pentadecane, trans-α-bergamotene, (E)-β-farnesene, and (6E,9E)-6,9-heptadecadiene, and some of these volatile compounds were terpenes, which varied among the different strains. Moreover, on the basis of hierarchical cluster analysis (HCA) and principal component analysis (PCA), the N. hybrid samples were divided into four groups: alcohols were the most important volatile compounds for Nh-4 samples; esters and aldehydes were the predominant volatiles in Nh-3 samples; and ketones and alkenes were important for Nh-2 samples. These compounds contribute to the unique flavors and aromas of the four strains of N. hybrid.

Highlights

Volatile organic compounds (VOCs) are involved in a wide range of functions in ornamental plants [1,2]
Using scanning electron microscopy (SEM), it was found that the cells on the surfaces of flower petals were irregular and massive, with abundant folds on the cell wall (Figure 1A)
The plastids were arranged along the cell wall in round or oval shapes, and a small number of starch grains and black oil droplets of different shapes and sizes were seen inside the plastids; these were the secreted osmiophilic matrix granules

Summary

Introduction

Volatile organic compounds (VOCs) are involved in a wide range of functions in ornamental plants [1,2]. VOCs have allelopathic effects on surrounding plants, protecting the plant and reducing damage from the outside world when they are injured [7,8] These compounds improve the aesthetic and economic value of plants, which are important indicators of the ornamental value of cut flowers and plants [9]. Due to the importance of VOCs emitted from plants, research on the floral substances of ornamental plants has gradually attracted attention This mainly involves the identification of plant volatiles, analyses of the main floral components, and the effects of volatile components on insect pollination behavior [10,11,12]. With the development of molecular biology, the anabolic pathways of floral substances have been gradually explored, and new methods have been developed for achieving genetic improvements of floral substances [13,14,15]

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Conclusion