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Vandegeer RK, Cibils‐Stewart X, Wuhrer R, Hartley SE, Tissue DT, Johnson SN. Leaf silicification provides herbivore defence regardless of the extensive impacts of water stress. Funct Ecol 2021. [DOI: 10.1111/1365-2435.13794] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Rebecca K. Vandegeer
- Hawkesbury Institute for the Environment Western Sydney University Penrith NSW Australia
| | - Ximena Cibils‐Stewart
- Hawkesbury Institute for the Environment Western Sydney University Penrith NSW Australia
- Instituto Nacional de Investigación Agropecuaria (INIA) Colonia Uruguay
| | - Richard Wuhrer
- Advanced Materials Characterisation Facility Western Sydney University Penrith NSW Australia
| | - Susan E. Hartley
- Department of Animal and Plant Sciences University of Sheffield Sheffield UK
| | - David T. Tissue
- Hawkesbury Institute for the Environment Western Sydney University Penrith NSW Australia
| | - Scott N. Johnson
- Hawkesbury Institute for the Environment Western Sydney University Penrith NSW Australia
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Biru FN, Islam T, Cibils-Stewart X, Cazzonelli CI, Elbaum R, Johnson SN. Anti-herbivore silicon defences in a model grass are greatest under Miocene levels of atmospheric CO 2. GLOBAL CHANGE BIOLOGY 2021; 27:2959-2969. [PMID: 33772982 DOI: 10.1111/gcb.15619] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Accepted: 03/12/2021] [Indexed: 06/12/2023]
Abstract
Silicon (Si) has an important role in mitigating diverse biotic and abiotic stresses in plants, mainly via the silicification of plant tissues. Environmental changes such as atmospheric CO2 concentrations may affect grass Si concentrations which, in turn, can alter herbivore performance. We recently demonstrated that pre-industrial atmospheric CO2 increased Si accumulation in Brachypodium distachyon grass, yet the patterns of Si deposition in leaves and whether this affects insect herbivore performance remains unknown. Moreover, it is unclear whether CO2 -driven changes in Si accumulation are linked to changes in gas exchange (e.g. transpiration rates). We therefore investigated how pre-industrial (reduced; rCO2 , 200 ppm), ambient (aCO2 , 410 ppm) and elevated (eCO2 , 640 ppm) CO2 concentrations, in combination with Si-treatment (Si+ or Si-), affected Si accumulation in B. distachyon and its subsequent effect on the performance of the global insect pest, Helicoverpa armigera. rCO2 increased Si concentrations by 29% and 36% compared to aCO2 and eCO2 respectively. These changes were not related to observed changes in gas exchange under different CO2 regimes, however. The increased Si accumulation under rCO2 decreased herbivore relative growth rate (RGR) by 120% relative to eCO2, whereas rCO2 caused herbivore RGR to decrease by 26% compared to eCO2 . Si supplementation also increased the density of macrohairs, silica and prickle cells, which was associated with reduced herbivore performance. There was a negative correlation among macrohair density, silica cell density, prickle cell density and herbivore RGR under rCO2 suggesting that these changes in leaf surface morphology were linked to reduced performance under this CO2 regime. To our knowledge, this is the first study to demonstrate that increased Si accumulation under pre-industrial CO2 reduces insect herbivore performance. Contrastingly, we found reduced Si accumulation under higher CO2 , which suggests that some grasses may become more susceptible to insect herbivores under projected climate change scenarios.
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Affiliation(s)
- Fikadu N Biru
- Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, Australia
- College of Agriculture and Veterinary Medicine, Jimma University, Jimma, Ethiopia
| | - Tarikul Islam
- Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, Australia
- Department of Entomology, Faculty of Agriculture, Bangladesh Agricultural University, Mymensingh, Bangladesh
| | - Ximena Cibils-Stewart
- Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, Australia
- Instituto Nacional de Investigación Agropecuaria (INIA), Colonia, Uruguay
| | | | - Rivka Elbaum
- R H Smith Institute of Plant Sciences and Genetics in Agriculture, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Scott N Johnson
- Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, Australia
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Vandegeer RK, Zhao C, Cibils-Stewart X, Wuhrer R, Hall CR, Hartley SE, Tissue DT, Johnson SN. Silicon deposition on guard cells increases stomatal sensitivity as mediated by K + efflux and consequently reduces stomatal conductance. PHYSIOLOGIA PLANTARUM 2021; 171:358-370. [PMID: 32880970 DOI: 10.1111/ppl.13202] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 08/27/2020] [Accepted: 09/01/2020] [Indexed: 06/11/2023]
Abstract
Silicon (Si) has been widely reported to improve plant resistance to water stress via various mechanisms including cuticular Si deposition to reduce leaf transpiration. However, there is limited understanding of the effects of Si on stomatal physiology, including the underlying mechanisms and implications for resistance to water stress. We grew tall fescue (Festuca arundinacea Schreb. cv. Fortuna) hydroponically, with or without Si, and treated half of the plants with 20% polyethylene glycol to impose physiological drought (osmotic stress). Scanning electron microscopy in conjunction with X-ray mapping found that Si was deposited on stomatal guard cells and as a sub-cuticular layer in Si-treated plants. Plants grown in Si had a 28% reduction in stomatal conductance and a 23% reduction in cuticular conductance. When abscisic acid was applied exogenously to epidermal leaf peels to promote stomatal closure, Si plants had 19% lower stomatal aperture compared to control plants (i.e. increased stomatal sensitivity) and an increased efflux of guard cell K+ ions. However, the changes in stomatal physiology with Si were not substantial enough to improve water stress resistance, as shown by a lack of significant effect of Si on water potential, growth, photosynthesis and water-use efficiency. Our findings suggest a novel underlying mechanism for reduced stomatal conductance with Si application; specifically, that Si deposition on stomatal guard cells promotes greater stomatal sensitivity as mediated by guard cell K+ efflux.
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Affiliation(s)
- Rebecca K Vandegeer
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, New South Wales, 2751, Australia
| | - Chenchen Zhao
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, New South Wales, 2751, Australia
| | - Ximena Cibils-Stewart
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, New South Wales, 2751, Australia
- Instituto Nacional de Investigación Agropecuaria (INIA), La Estanzuela Research Station, Ruta 50, Km. 11, Colonia, Uruguay
| | - Richard Wuhrer
- Advanced Materials Characterisation Facility (AMCF), Western Sydney University, Locked Bag 1797, Penrith, New South Wales, 2751, Australia
| | - Casey R Hall
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, New South Wales, 2751, Australia
| | - Susan E Hartley
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield, S10 2TN, UK
| | - David T Tissue
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, New South Wales, 2751, Australia
| | - Scott N Johnson
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, New South Wales, 2751, Australia
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