1 Beijing Key Laboratory of Ornamental Plants Germplasm Innovation and Molecular Breeding, Beijing Laboratory of Urban and Rural Ecological Environment, Key Laboratory of Genetics and Breeding in Forest Trees and Ornamental Plants of Ministry of Education, National Engineering Research Center for Floriculture, School of Landscape Architecture, Beijing Forestry University, Beijing 100083, China
Rosa laxa is widely distributed in the Xinjiang Uygur Autonomous Region of China and is highly adaptable and rich in variation. In this study, we investigated the morphology, habitats, and palynomorphology of R. laxa botanical varieties from Xinjiang, China. In addition to R. laxa var. laxa, there were three other botanical varieties of R. laxa growing in southern Xinjiang, including var. mollis, var. kaschgarica, and var. tomurensis. Together, these four botanical varieties exhibited morphological variation, mainly in the morphology of prickles and the glandular trichome and in flower color. The pollen grains of the R. laxa botanical varieties, all medium in size (21.77–48.39 μm), came in three shapes: perprolate, prolate, and subspheroidal. Their pollen exine sculptures were characterized by either a striate-perforation pattern or striate pattern, but perforation varied in terms of diameter and density and striae varied in depth and density. Palynomorphological assessment showed that three types of evolution, i.e., primitive, transitive, and evolved, were present among R. laxa botanical varieties, and pollen dimorphism was observed in the same botanical variety. Perprolate pollen with a dense striate pattern was the most evolved type. Based on morphological and palynomorphological investigations, var. tomurensis was considered to be the most evolved one among the studied botanical varieties.
We would like to thank C.Y. Ling, L.L. Dong, Y. Jiang, G.Z. Mo, J.G. Liang, H. Xue, J.X. Liu, and Y.H. Wang of Beijing Forestry University for helping in the survey; and D. Luo, V. Jens, X.M. Xu, L. Suzanne, L. Anny, Y. Kong, J.R. Bai, Y. Vanessa, and F. Qing for their comments and discussion.
This research was supported by the Fundamental Research Funds for the Central Universities (No. 2015ZCQ-YL-03) and National Natural Science Foundation of China (31600565).
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