Abstract
Leaf shape, including leaf size, leaf dissection index (LDI), and venation distribution, strongly impacts leaf physiology and the forces of momentum exerted on leaves or the canopy under windy conditions. Yet, little has been known about how leaf shape affects the morphological response of trees to wind load. We studied eight Quercus species, with different leaf shapes, to determine the morphological response to simulated wind load. Quercus trees with long elliptical leaves, were significantly affected by wind load (P< 0.05), as indicted by smaller specific leaf area (SLA), stem base diameter and stem height under windy conditions when compared to the control. The Quercus trees with leaves characterized by lanceolate or sinuous edges, showed positive morphological responses to wind load, such as bigger leaf thickness, larger stem diameter, allocation to root biomass, and smaller stem height (P< 0.05). These morphological responses to wind can reduce drag and increase the mechanical strength of the tree. Leaf dissection index (LDI), an important index of leaf shape, was correlated with morphological response to wind load (P< 0.05), including differences in SLA, in stem base diameter and in allocation to root biomass. These results suggest that trees with higher LDI, such as those with more and/or deeper lobes, are better adapted to wind load.
Highlights
Thigmomorphogenesis is the response of plants to mechanical sensation, such as wind or raindrops, by altering their growth patterns [1,2,3]
Leaf length was significantly shorter by 12.43%– 17.56% for Q. acutissima, Q. palustirs and Q. coccinea, while leaf thickness or vein thickness was significantly bigger by 8.40%– 31.85% for Q. virginiana, Q. phellos, Q. rubra, Q. texana, Q. palustris and Q. coccinea under T2 than those under CK (Table 1)
The growth of stem height under T1was significantly higher for Q. falcta, Q. texana, Q. palustris and Q. coccinea than that under CK, and it is same under T2 for all species (Fig 3A, S2 Table)
Summary
Thigmomorphogenesis is the response of plants to mechanical sensation, such as wind or raindrops, by altering their growth patterns [1,2,3]. It generally results in common morphological variation among plants without phylogenesis [4,5]. Trees are subject to greater impacts from wind load than other plants due to their tall stature [9]. Trees may develop a “stunted” appearance under wind load, which can decrease the speed-specific drag of the crown [7, 10].
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