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 been proposed too, though 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 analyze 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: 282 vascular plant species in predominantly
herbaceous communities. Methods: We compiled a dataset for leaf silicon
concentration [Si] across 27 sites and 153 herbaceous plots comprising 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]
is consistently positively correlated with mean wind speed among species
across China. For the seven widespread monocot species with high leaf
[Si], including the globally widely distributed common reed (Phragmites
australis), intraspecific variation in leaf [Si] follows the same
consistent positive correlation with mean wind speed. Main conclusions:
Our findings suggest 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, and hence these findings are of global
significance and indicate further research into large scale variation of
leaf Si and mechanical traits in relation to wind exposure will likely be
illuminating.