Agricultural College, Guizhou University, Guiyang, China.
Guizhou Engineering Research Center for fruit Crops, Guiyang, China.
Microsc Res Tech. 2021 Sep;84(9):2095-2103. doi: 10.1002/jemt.23765. Epub 2021 May 2.
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.
板栗蔷薇（R. roxburghii Tratt.）（蔷薇科）（RR）因其营养价值和药用价值在中国是一种重要的作物。RR 经常在各种器官的表面产生毛状体，然而毛状体的发育受到遗传因素的控制，一些品种的毛状体明显少于其他品种。某些品种的果实表面覆盖着厚厚的宏观毛状体，这对于果实加工和食用来说是不理想的。然而，存在光滑果实品种，如 R. roxburghii Tratt. f. esetosa Ku（RRE）。尽管它们具有经济重要性，但这两种栗蔷薇种质的毛状体解剖结构尚未详细研究。在这里，我们使用透射电子显微镜（TEM）研究 RR 和 RRE 的茎、萼片和果实上分布的毛状体的超微结构。RR 和 RRE 茎刺毛状体的内部结构呈椭圆形，不含核仁或其他细胞器。RR 茎刺的细胞壁较厚，细胞间隙充满液体，而 RRE 茎刺的细胞壁较薄，细胞间隙充满空气。RR 的萼片针状毛状体和 RRE 的萼片腺毛状体（GTs）的细胞具有相似的液泡大小、细胞质含量、细胞间隙和细胞内质体的排列。然而，RRE 的 GTs 中存在嗜锇颗粒。这两种种质的萼片的鞭状毛状体由椭圆形或棒状细胞组成。尽管这两种种质的萼片的鞭状毛状体具有相似的内部结构，并且都含有淀粉粒和可见类囊体膜的质体，但 RR 萼片的鞭状毛状体的细胞壁较薄，细胞质比例较高，分布更均匀。RR 萼片的鞭状毛状体中存在着被锇酸强烈染色的颗粒，而 RRE 中则很少出现。在 RR 的果实针状毛状体上，RR 的果实鞭状毛状体和 RRE 的果实 GTs 具有相似的细胞形态、排列和液泡大小以及细胞间隙。RR 的果实鞭状毛状体和 GTs 以及 RRE 的果实 GTs 都含有被锇酸强烈染色的颗粒，并且 GTs 含有质体和淀粉粒。这些毛状体细胞超微结构的差异可能与毛状体的发育过程或生物学功能有关。这些结果还表明，这两种栗蔷薇种质是进一步研究该属毛状体发生和随后在该物种中培育光滑器官性状的良好候选材料。
