Dose invasion process influence stomatal traits in Reynoutria japonica?

Xiaojuan Wang1, Peipei Cao2, Bo Li2,3
1. Natural History Research Center, Shanghai Natural History Museum, Shanghai Science & Technology Museum, 200127 Shanghai, China; 2. Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, National Observations and Research Station for Wetland Ecosystems of the Yangtze Estuary, School of Life Sciences, Fudan University, Shanghai, 200438 China; 3. Ministry of Education Key Laboratory for Transboundary Ecosecurity of Southwest China, School of Ecology and Environmental Science, Yunnan University, Kunming, 650504 Yunnan China

Knotweed (Reynoutria japonica) is native plant to East Asia, and has been introduced to West where it is invasive weed for causing economic or ecological losses. However, a more extensive effort is needed to better understand the invasiveness. Using the data of Knotweed leaf stomatal traits, the aim of this study focused on the micro-mechanisms for its fast expansion after the introduction. We used a common garden experiment with 532 plants from the invasive ranges in West (Europe and U.S.), and their native ranges in East Asia (Japan and China). Original data on stomatal apparatus parameters were investigated by scanning electron microscopy (SEM). Our results showed that stomatal density (SD) and stomatal index (SI) of invasive plants were higher in introduced ranges than in native ranges(P<0.001), whereas stomatal size (SS, guard cell length) was not significantly different between introduced and native ranges. SD and SI varied from 34 to 228 per mm2 and from 10.87% to 67.12%, respectively. Our results suggested that invasion process has profound impacts on the selective pressures shaping SD and SI in Knotweed plants. Stomatal traits could have high environmental plasticity, and invasiveness may be due to the strategy for increase in the number of stomata.