Rosa roxburghii Tratt (Rosaceae) of various organ surfaces are widely existing trichomes. Certain varieties have fruits that are thickly covered with macroscopic trichomes. R. roxburghii Tratt (RR) and R. roxburghii Tratt. f. esetosa Ku (RRE) are important commercial horticultural crops in China because of their nutritional and medicinal values. RRE is generally considered a smooth-fruit variant that arose from RR. Despite their economic importance, the morphological and anatomic features of organ trichomes have not been explored in detail for these two rose germplasms. In this research, we investigated the distribution, morphology, and structure of trichomes distributed on the stem, pedicel, fruit, sepal, and marginal lobule sepals (MLS) of RR as well as RRE. This was accomplished using scanning electron microscopy (SEM). There are various shapes of trichomes distributed on the surfaces of stems, pedicels, fruits, and sepals of the two germplasms. Binate prickles arose on the stem nodes in both germplasms, but acicular trichomes, papillary trichomes, and ribbon trichomes were present only on the surfaces of pedicels in RR. Likewise, flagelliform trichomes were present only on the surfaces of pedicels in RRE. Furthermore, a transection of stems shows that thorns in the two germplasms are composed of epidermis, meristematic layer, and parenchyma cells. The trichome epidermis and meristematic layer in stems of RR are composed of round cells, whereas RRE exhibits square cells in the same layers. Trichomes on the fruit of RR were macroscopic and of single flagelliform and acicular shape. RRE exhibited polymorphic trichomes of flagelliform, triangular, capitate glandular, and elliptic glandular shapes on the pericarp. On the surfaces of RR sepals, there are thick macroscopic acicular trichomes. In contrast, RRE sepals presented flagelliform trichomes and capitate glandular trichomes. It is interesting that no trichomes were found on the surfaces of the MLS in the two germplasms; however, stomata were densely packed on the MLS of RRE when compared with RR. For RR, the trichomes on both sepal and fruit are composed of an epidermis layer and parenchyma cells; however, the epidermis cells of sepal trichomes are polygon-shaped, in contrast to the round epidermis cells in fruit. These results suggest that the two rose germplasms are good candidates for understanding the trichome ontogeny in the genus and for further breeding of the smooth organ trait in this rose species.
Dao-Jing Wang, Jing-Wen Zeng, Wen-Tao Ma, Min Lu and Hua-Ming An
Shugang Zhao, Jiamin Niu, Linying Yun, Kai Liu, Shuang Wang, Jing Wen, Hongxia Wang and ZhiHua Zhang
The role of the walnut (Juglans regia L.) shell in nut development, transportation, cleaning, and storage is often ignored. The shell suture seal and thickness are directly associated with kernel characteristics. In the present study, shell differentiation and microstructure were observed with an optical microscope using paraffin-sectioning and cryosectioning. The results showed that the parenchymal cells of the endocarp began to differentiate into sclerenchymal cells from 49 d after flowering (DAF), and the entire process continued until fruit maturation. The mature shell consists of three parts, including the sclereid layer (L1), sclerenchymal cell layer (L2), and shrunken cell layer (L3), from the outside to the inside. The shell thickness, suture seal grade, and mechanical strength were evaluated, as well as the lignin, cellulose, and phenolic compounds of the shell. Suture seal grade was positively correlated with lignin content, shell thickness, and L1 thickness and negatively correlated with shell cell diameter. Similarly, the mechanical strength of the shell was positively correlated with lignin content and L1 thickness. ‘Qingxing’ fruits were subjected to two treatments, namely, 30% shading and 70% shading, from 10 d after anthesis to maturity, with no shading used as control. After harvesting in September, nutshell sections showed thinner shells, with decreased contents of lignin and polyphenols, obtained under shaded conditions, and two of the three parts of the shell changed dramatically. The thinning of L1 and thickening of L3 eventually led to a thinner shell. The aim of this study was to evaluate the relationship among the shell structure, cellular components, and physical properties and provide a theoretical basis for cultivar breeding, rational planting density, and regulation of shell development.
Zhi-li Suo, Xiao-qing Zhao, Jing-yu Sun and Wen-hai Sun
There exist large accumulations of natural genetic diversifications under the natural and artificial selections on the flower among the Chinese tree peony cultivars incited by ornamental and medicinal uses in the past over 1500 years in China. Paeonia suffruticosa `Xiao Ci Wei' is a unique Chinese tree peony cultivar possessing special bicolored petals with tubular tip structure (Paeoniaceae). This natural mutant is not only a unique ornamental, but also a valuable material for scientific researches in Evodevotics.