Stomatal variation endows Solidago canadensis with successful invasion through polyploidization

Huan Zhang1, Zhongsai Tian1, Xiaojuan Wang2, Sheng Qiang1*
1 Weed Research Laboratory, College of Life Science, Nanjing Agricultural University, Nanjing 210095, China; 2 Natural History Research Center, Shanghai Natural History Museum, Shanghai Science & Technology Museum, Shanghai 200127, China

Solidago canadensis, native to temperate North America, has successfully invaded subtropical regions of China through polyploidization. However, whether the variation of stomata on the leaf epidermis contributes to its successful invasion remains largely unknown. A total of 203 plant individual leaves from 67 sampling sites of Solidago canadensis L. worldwide were observed using optical and electric microscopes. It was showed that the stomata types of S. canadensis were all reniform isopachy wall type and anomocytic type. Stomata were mainly distributed randomly in inter-veins of the lower epidermis amomg all six geo-cytotypes. However, hexploid was found fewer stomata in the lower epidermis. There was a significant positive correlation between ploidy levels and stomatal density, size and the thickness of guard cell wall. Hexaploid had larger and rounder stomata, more types of denser trichomes, and a higher degree of waxy coverage than diploids, However, there was no difference in stomatal size and number between the native and the introduced populations, but the wax content and the complexity of surface trichomes were higher in the introduced range than in the native range. Thus, the adaptive differentiation in the stomata of different geocytotypes of S. canadensis may play an important role in its successful invasion into new environment.