Comparative ultrastructure of trichomes on various organs of Rosa roxburghii

Abstract

Chestnut rose, R. roxburghii Tratt. (Rosaceae) (RR) is an important crop in China due to its nutritional and medicinal values. RR frequently produces trichomes on the surfaces of a diverse range of organs, however a genetic component exists to the control of trichome development, with some cultivars having significantly fewer trichomes to others. Certain varieties have fruits that are thickly covered with macroscopic trichomes, which is an undesirable trait for fruit processing and consumption. However, smooth‐fruit cultivars exist, such as R. roxburghii Tratt. f. esetosa Ku (RRE). Despite their economic importance, the anatomical features of trichomes have not been explored in detail for these two chestnut rose germplasms. Here, we investigate the ultrastructure of trichomes distributed on the stem, sepal, and fruit of RR and RRE using transmission electron microscopy (TEM). The internal structure of stem prickle trichomes in RR and RRE was oval in shape and did not contain nucleoli or other organelles. The cell walls of stem prickles in RR are thick and the intercellular spaces occupied with liquid, whereas the cells wall of stem prickles in RRE are thin and have air‐filled intercellular spaces. The cells of sepal acicular trichomes in RR and glandular trichomes (GTs) of sepals in RRE had similar vacuole sizes, cytoplasm content, intercellular spaces, and arrangement of plastids within cells. However, there were osmiophilic granules present in the GTs of RRE. The flagelliform trichomes in the sepals of the two germplasms are composed of oval or rod‐shaped cells. Although the flagelliform trichomes in the sepals of the two germplasms had a similar internal structure, and both contained starch grains and plastids with visible thylakoid membranes, the flagelliform trichomes in the sepals of RR had a thinner cell wall and a higher proportion of cytoplasm which was more evenly distributed across the cell. There were granules that stained heavily with osmium tetroxide which occurred infrequently in the flagelliform trichomes of sepals in RRE but were not observed in RR. On the acicular trichomes of fruit in RR, the flagelliform trichomes and the GTs of fruit in RRE shared similar cell morphology, arrangement and vacuole size as well as intercellular space. Both the fruit flagelliform trichomes and GTs in RRE contain granules which stain heavily with osmium tetroxide, and the GTs contain plastids and starch grains. These differences in trichome cell ultrastructure may be related to developmental processes or biological functions of the trichomes. These results also suggest that the two chestnut rose germplasms are good candidates for further study of trichome ontogeny in the genus and subsequent breeding of the smooth organ trait in this species.

Chitosan Can Induce Rosa roxburghii Tratt. against Sphaerotheca sp. and Enhance Its Resistance, Photosynthesis, Yield, and Quality

“…Rosa roxburghii Tratt., a Rosaceae deciduous shrub, is rich in antioxidants and nutrients, such as vitamin C, flavonoids, superoxide dismutase (SOD), and various minerals [1][2][3]. Due to its high nutritional and medical value, it is widely used in improving immunity, lowering blood pressure, regulating the digestive system, protecting the liver, as well as anti-oxidation, anti-cancer, antibacterial, and anti-radiation, etc.…”

“…As a promising fruit crop and natural medicine, R. roxburghii is widely planted in Southwest China, especially in Guizhou Province. Recently, Guizhou's R. roxburghii industry has developed rapidly and made great contributions to rocky desertification control, poverty alleviation, and rural revitalization, and its planting area reached 170,000 hm 2 in 2020 [3,9]. However, as commercial cultivation of R. roxburghii expanded, many pests became increasingly serious such as Sphaerotheca sp., Grapholita molesta, and Cercospora insulana Sacc, which seriously affect the yield and quality of R. roxburghii and frequently cause great economic losses.…”

Co-Application of Allicin and Chitosan Increases Resistance of Rosa roxburghii against Powdery Mildew and Enhances Its Yield and Quality

“…Rosa roxburghii Tratt., an edible and medicinal fruit rich in vitamin C, flavonoids, superoxide dismutase (SOD) and various minerals, has high medicinal and nutritional values [1][2][3][4][5]. Recently, the R. roxburghii industry has developed rapidly in southwest China, especially in Guizhou Province, where the planting areas reached 170,000 hm 2 in 2020 [3,6]. Powdery mildew, caused by Sphaerotheca sp., is the most serious disease regarding R. roxburghii production [1].…”

“…Rosa roxburghii Tratt., an edible and medicinal fruit rich in vitamin C, flavonoids, superoxide dismutase (SOD) and various minerals, has high medicinal and nutritional values [ 1 , 2 , 3 , 4 , 5 ]. Recently, the R .…”

“…Recently, the R . roxburghii industry has developed rapidly in southwest China, especially in Guizhou Province, where the planting areas reached 170,000 hm 2 in 2020 [ 3 , 6 ]. Powdery mildew, caused by Sphaerotheca sp., is the most serious disease regarding R. roxburghii production [ 1 ].…”