Abstract
Rhus potaninii Maxim is an economically and medicinally important tree species in China. It produces galls (induced by aphids) with a high abundance of tannins. Here, we discuss the histology, cellular structures and their distribution, and the macromolecular components of secretive glandular trichomes on the leaves of R. potaninii. A variation in the density of glandular trichomes and tomenta was found between the adaxial and abaxial sides of a leaf in different regions and stages of the leaf. The glandular trichomes on R. potaninii trees comprise a stalk with no cellular structure and a head with 8–15 cells. Based on staining, we found that the secretion of glandular trichomes has many polysaccharides, phenolic compounds, and acidic lipids but very few neutral lipids. The dense glandular trichomes provide mechanical protection for young tissues; additionally, their secretion protects the young tissues from pathogens by a special chemical component. According to transcriptome analysis, we found enhanced biosynthetic and metabolism pathways of glycan, lipids, toxic amino acids, and phenylpropanoids. This shows a similar tendency to the staining. The numbers of differentially expressed genes were large or small; the averaged range of upregulated genes was greater than that of the downregulated genes in most subpathways. Some selectively expressed genes were found in glandular trichomes, responsible for the chitinase activity and pathogenesis-related proteins, which all have antibacterial activity and serve for plant defense. To our knowledge, this is the first study showing the components of the secretion from glandular trichomes on the leaf surface of R. potaninii.
Highlights
Plants possess several microstructures which are not visible to the eyes
The heads were divided into several parts through grooves, which appeared as interspaces between cells under a scanning electron microscope (SEM) (Figure 1c)
The glandular trichomes (GTs) on R. potaninii leaves look like grenades, with a slender stalk and an expanded head with 8–15 cells
Summary
Plants possess several microstructures which are not visible to the eyes These structures usually play important roles in different stages of plant life. Stomata are responsible for gas exchange in plants, i.e., in respiration and photosynthesis [1]. Another important accessory structure of plant is trichomes. GTs exist in different forms, such as peltate, capitate, and ball forms [5]. They exhibit tremendous species-specific characteristics [6]. Some GTs consist of a globular base with multiple cells and a small head with a single glandular cell; some consist of 4–8 cells and a noncellular stalk, while some have just a few cells without a stalk [7,8]
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