Characteristics Of Silicon Contents And Their Relationship To Environmental Factorsin Wetland Herbaceous Plants

Silicon is distributed in nature extensively, and it is found in all plants that growing on the soil. There is a strong silicon cycle in plant-soil system. Si is an essential element for silicophilic plants, such as grass (Poaceae), sedge (Cyperaceae). It was also propitious for the growth of non-siliconphile plants. Si plays an important role in plant ecological responses and effects during the life cycle.There are large amount of silicophilic plants and they generally owns huge plant biomass, so wetland system is an ideal condition for the research of leaf Si content. Meanwhile, the pattern of plant silicon can contribute to our understanding of the function and biogeochemical cycle of leaf Si, and improve the dataset of Si.In the present study, we compiled a national dataset of leaf Si content and environmental variables for herbaceous plants in 27 China wetland through filed investigation. We focused on:(1) the distribution character of herbaceous leaf Si content in main wetlands of China (2) the relationship between leaf Si content and phylogeny, (3) the relationship between leaf Si content and climate variables, soil silicon content and wind speed factors among four Family (Poaceae, Cyperaceae, Asteraceae & Fabaceae).The results point to the following:(1) There are great variations in leaf Si content of herbaceous plants among main wetlands of China. Herbaceous leaf Si content of main wetlands of China is generally about 0.1% to 10% of plant biomass, i.e.1-100 mg g-1, and most distributed at 3% or less.(2) There are significant difference in leaf Si content among different species Leaf Si content of monocots scatters in 70 mg g-1 or less, and dicots are distributed in 30 mg g-1 or less. Leaf Si content of monocots was significantly higher than dicots. Some species showed higher Si accumulation, such as Equisetum, Poaceae, Cyperaceae and Commelinaceae.(3) The contribution degrees of the variation of Si content are different at different level of systematic classification. Phylum could explain 71.04% of the total variation. Order, Family and Species could explain 7.27%,5.74%,15.94% of the total variance, respectively. While, there are almost no contribution to the total variation at the level of Classes and Genus.(4) Monocots, such as Poaceae, Commelinaceae and Cyperaceae, was significantly higher than others in leaf Si content, and they all belong to the Commelinids. But high Si content of leaf is not a common feature in Commelinids. The accumulation of Si in leaf among Poaceae, Commelinaceae and Cyperaceae may due to their adaptation to environment in early evolutionary time.(5) Leaf Si content of herbaceous plant are significantly different in 27 main wetlands of China, and it is especially lower in Zoige wetland and Sishui River. There are also significantly difference in leaf Si content of herbaceous plants among difference climate zones. Herbaceous leaf Si content of plateau temperate humid& semi-humid climate zone is significantly lower than non-plateau climate zone. With increase of altitude, the variation of herbaceous leaf Si content among 27 main wetlands of China decrease. This was because the proportion of Poaceae decreased in high altitude.(6) The relationship between leaf Si content of Poaceae and Cyperaceae and environmental variables is different from Asteraceae and Fabaceae. This may be caused by different phylogeny. Overall, leaf Si content of Poaceae, Cyperaceae, Asteraceae and Fabaceae was negatively correlated with precipitation and leaf Si content of Poaceae and Cyperaceae was positively correlated with available Si content in soil. While, leaf Si content of Asteraceae and Fabaceae showed no significant relationship between leaf Si content and available Si content in soil.(7) Wind-induced mechanical stimulation is an important factor affecting plant leaf Si content, the correlation coefficient between the intensity of wind-induced mechanical stimulation and plant leaf Si element content is large than others. Overall, the plant leaf Si content and the intensity of wind-induced mechanical stimulation is positively correlated. With the increase of the intensity of wind-induced mechanical stimulation, plant leaf Si content increases in a large regional scale.