Association of leaf silicon content with chronic wind exposure across and within herbaceous plant species

Aim: High foliar silicon (henceforth Si) concentration protects plant tissues against herbivory, but protection against several abiotic stressors has also been proposed, although the adaptive significance of these functions is still being debated. We aimed to explore the potential relationships between foliar Si content and chronic wind exposure across a large scale and multiple species and to analyse an overlooked alternative or complementary function of silicon in leaves: mechanical protection against wind. Location: Mainland China. Time period: From July to September during 2012–2014. Major taxa studied: Two hundred and eighty-two vascular plant species in predominantly herbaceous communities. Methods: We compiled a dataset for leaf silicon concentration ([Si]) across 27 sites and 153 herbaceous plots within the major climate zones of China. We hypothesized that evolutionary lineages that generally have high [Si] should show positive relationships between leaf [Si] and mean annual wind speed. Results: Within major families with generally high [Si] (especially grasses, sedges and composites), leaf [Si] exhibits a consistently positive correlation with mean wind speed among species across China. For the seven widespread monocot species with high leaf [Si], including the globally distributed common reed (Phragmites australis), intraspecific variation in leaf [Si] exhibits the same consistent positive correlation with mean wind speed. Main conclusions: Our findings suggest that high leaf [Si] is likely to have widespread adaptive value for wind exposure of leaves, at least in several very widespread families and species of herbaceous plants. Damage from wind is a danger for plants in many ecosystems, hence these findings are of global significance and indicate that further research into large-scale variation of leaf Si and mechanical traits in relationship to wind exposure is likely to be illuminating.