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Open AccessArticle

Silicon Alters Leaf Surface Morphology and Suppresses Insect Herbivory in a Model Grass Species

Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith NSW 2751, Australia
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Plants 2020, 9(5), 643; https://doi.org/10.3390/plants9050643
Received: 4 May 2020 / Revised: 15 May 2020 / Accepted: 16 May 2020 / Published: 19 May 2020
(This article belongs to the Special Issue The Role of Silicon in Plant Defences)
Grasses accumulate large amounts of silicon (Si) which is deposited in trichomes, specialised silica cells and cell walls. This may increase leaf toughness and reduce cell rupture, palatability and digestion. Few studies have measured leaf mechanical traits in response to Si, thus the effect of Si on herbivores can be difficult to disentangle from Si-induced changes in leaf surface morphology. We assessed the effects of Si on Brachypodium distachyon mechanical traits (specific leaf area (SLA), thickness, leaf dry matter content (LDMC), relative electrolyte leakage (REL)) and leaf surface morphology (macrohairs, prickle, silica and epidermal cells) and determined the effects of Si on the growth of two generalist insect herbivores (Helicoverpa armigera and Acheta domesticus). Si had no effect on leaf mechanical traits; however, Si changed leaf surface morphology: silica and prickle cells were on average 127% and 36% larger in Si supplemented plants, respectively. Prickle cell density was significantly reduced by Si, while macrohair density remained unchanged. Caterpillars were more negatively affected by Si compared to crickets, possibly due to the latter having a thicker and thus more protective gut lining. Our data show that Si acts as a direct defence against leaf-chewing insects by changing the morphology of specialised defence structures without altering leaf mechanical traits. View Full-Text
Keywords: insect herbivores; silica; trichomes; epidermal cells; Poaceae; plant defence; Orthoptera; Lepidoptera insect herbivores; silica; trichomes; epidermal cells; Poaceae; plant defence; Orthoptera; Lepidoptera
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MDPI and ACS Style

Hall, C.R.; Dagg, V.; Waterman, J.M.; Johnson, S.N. Silicon Alters Leaf Surface Morphology and Suppresses Insect Herbivory in a Model Grass Species. Plants 2020, 9, 643.

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