Abstract
Abstract Silicon (Si) supplementation can enhance symbiotic functions in some legumes (Fabaceae) with their nitrogen‐fixing rhizobia, such as root nodulation and nitrogen fixation. However, it is still poorly understood how Si influences legume–insect interactions. Here, we investigated how a symbiotic legume responds not only to Si supplementation but also to herbivory treatment with varying infestation levels in two events. We conducted a controlled climate chamber experiment by growing Medicago truncatula plants inoculated with rhizobia. For half of the plants, the soil was kept without Si (−Si), whereas the other half was regularly supplemented with Si (+Si). We then infested the plants with caterpillars of Spodoptera littoralis with 0, 1 or 3 larvae and 0, 1 or 1 larva in single herbivory attack and in double herbivory attack, respectively. To understand plant responses to such treatment combinations, we examined 16 functional traits. Nodule number, nodule fresh mass and nodule leghaemoglobin concentrations were not affected in single attack plants. However, increasing levels of herbivory led to decreases in such measured traits in double attack plants. Foliar C to N ratio increased in single attack plants but decreased in double attack plants with increasing levels of herbivory, indicating contrasting resource allocation. Herbivory did not affect the content of foliar Si, which was higher in +Si than −Si plants. Si and herbivory led to reduced foliar phenolics in double attack plants, suggesting a potential trade‐off between silicification and phenolic production. Si and herbivory led to increased trichome densities in single attack plants, but patterns were less clear in double attack plants. Herbivory but not Si reduced plant biomass with increasing levels of herbivory in double attack plants. Relative growth rates of the caterpillars, as proxy for plant resistance, decreased mainly due to herbivory treatment, when fed on single attack plants. Using a trait‐based approach, we provide novel insights to better understand the response of a legume to Si supplementation and different herbivory levels and events. We conclude that herbivory predominantly exerts much stronger effects than Si on various plant traits, pointing to a necessity to respond to herbivory by induced defence strategies. Read the free Plain Language Summary for this article on the Journal blog.
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Claims 14
Claim · model-written summary
Nodule number, fresh mass and leghaemoglobin concentration did not change in single-attack plants.
- Taxon
- Medicago truncatula
Medicago truncatulae1 - Treatment
- single attacke0
- Interactor
- rhizobiae1symbiont
- Outcome
- Nodule number, nodule fresh mass and nodule leghaemoglobin concentrationse0
- Direction
- not affectede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nodule number, nodule fresh mass and nodule leghaemoglobin concentrations were not affected in single attack plants”
e1“Medicago truncatula plants inoculated with rhizobia”
Claim · model-written summary
Increasing herbivory decreased nodule number, fresh mass and leghaemoglobin in double-attack plants.
- Taxon
- Medicago truncatulaMedicago truncatulae2
- Treatment
- increasing levels of herbivorye0
- Interactor
- Spodoptera littoralis
Spodoptera littoralise3herbivore - Second interactor
- rhizobiae2symbiont
- Outcome
- Nodule number, nodule fresh mass and nodule leghaemoglobin concentrationse1
- Direction
- decreasese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increasing levels of herbivory led to decreases in such measured traits in double attack plants”
e1“Nodule number, nodule fresh mass and nodule leghaemoglobin concentrations”
e2“Medicago truncatula plants inoculated with rhizobia”
e3“caterpillars of Spodoptera littoralis”
Claim · model-written summary
Increasing herbivory raised foliar C to N ratio after a single attack.
- Taxon
- Medicago truncatulaMedicago truncatulae1
- Treatment
- increasing levels of herbivorye0
- Interactor
- Spodoptera littoralisSpodoptera littoralise2herbivore
- Outcome
- Foliar C to N ratioe0
- Direction
- increasede0
- Qualifier
- single attack plantse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Foliar C to N ratio increased in single attack plants but decreased in double attack plants with increasing levels of herbivory”
e1“Medicago truncatula plants”
e2“Spodoptera littoralis”
Claim · model-written summary
Increasing herbivory lowered foliar C to N ratio after double attacks.
- Taxon
- Medicago truncatulaMedicago truncatulae1
- Treatment
- increasing levels of herbivorye0
- Interactor
- Spodoptera littoralisSpodoptera littoralise2herbivore
- Outcome
- Foliar C to N ratioe0
- Direction
- decreasede0
- Qualifier
- double attack plantse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Foliar C to N ratio increased in single attack plants but decreased in double attack plants with increasing levels of herbivory”
e1“Medicago truncatula plants”
e2“Spodoptera littoralis”
Claim · model-written summary
Herbivory did not change foliar silicon content.
- Taxon
- Medicago truncatulaMedicago truncatulae1
- Treatment
- Herbivorye0
- Interactor
- Spodoptera littoralisSpodoptera littoralise2herbivore
- Outcome
- content of foliar Sie0
- Direction
- did not affecte0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Herbivory did not affect the content of foliar Si”
e1“Medicago truncatula plants”
e2“Spodoptera littoralis”
Claim · model-written summary
Silicon supplementation raised foliar silicon content.
- Taxon
- Medicago truncatulaMedicago truncatulae2
- Treatment
- +Sie0
- Outcome
- content of foliar Sie1
- Direction
- highere0
- Comparator
- −Si plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“which was higher in +Si than −Si plants”
e1“content of foliar Si”
e2“Medicago truncatula plants”
Claim · model-written summary
Silicon and herbivory reduced foliar phenolics in double-attack plants.
- Taxon
- Medicago truncatulaMedicago truncatulae1
- Treatment
- Si and herbivorye0
- Interactor
- Spodoptera littoralisSpodoptera littoralise2herbivore
- Outcome
- foliar phenolicse0
- Direction
- reducede0
- Qualifier
- double attack plantse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Si and herbivory led to reduced foliar phenolics in double attack plants”
e1“Medicago truncatula plants”
e2“Spodoptera littoralis”
Claim · model-written summary
Silicon and herbivory increased trichome density in single-attack plants.
- Taxon
- Medicago truncatulaMedicago truncatulae1
- Treatment
- Si and herbivorye0
- Interactor
- Spodoptera littoralisSpodoptera littoralise2herbivore
- Outcome
- trichome densitiese0
- Direction
- increasede0
- Qualifier
- single attack plantse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Si and herbivory led to increased trichome densities in single attack plants”
e1“Medicago truncatula plants”
e2“Spodoptera littoralis”
Claim · model-written summary
Trichome density patterns were less clear after double attacks.
- Taxon
- Medicago truncatulaMedicago truncatulae2
- Outcome
- trichome densitiese1
- Qualifier
- patterns were less clear in double attack plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“patterns were less clear in double attack plants”
e1“trichome densities”
e2“Medicago truncatula plants”
Claim · model-written summary
Herbivory reduced plant biomass with increasing intensity after double attacks.
- Taxon
- Medicago truncatulaMedicago truncatulae1
- Treatment
- Herbivorye0
- Interactor
- Spodoptera littoralisSpodoptera littoralise2herbivore
- Outcome
- plant biomasse0
- Direction
- reducede0
- Qualifier
- double attack plantse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Herbivory but not Si reduced plant biomass with increasing levels of herbivory in double attack plants”
e1“Medicago truncatula plants”
e2“Spodoptera littoralis”
Claim · model-written summary
Silicon did not reduce plant biomass after double attacks.
- Taxon
- Medicago truncatulaMedicago truncatulae1
- Treatment
- Sie0
- Outcome
- plant biomasse0
- Direction
- not Si reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Herbivory but not Si reduced plant biomass with increasing levels of herbivory in double attack plants”
e1“Medicago truncatula plants”
Claim · model-written summary
Caterpillar relative growth rates declined mainly due to herbivory treatment when fed single-attack plants.
- Taxon
- Medicago truncatulaMedicago truncatulae1
- Treatment
- herbivory treatmente0
- Interactor
- Spodoptera littoralisSpodoptera littoralise2herbivore
- Outcome
- Relative growth rates of the caterpillarse0
- Direction
- decreasede0
- Qualifier
- single attack plantse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Relative growth rates of the caterpillars, as proxy for plant resistance, decreased mainly due to herbivory treatment, when fed on single attack plants”
e1“Medicago truncatula plants”
e2“Spodoptera littoralis”
Claim · model-written summary
The authors concluded herbivory had stronger effects on plant traits than silicon supplementation.
- Taxon
- Medicago truncatulaMedicago truncatulae1
- Interactor
- Spodoptera littoralisSpodoptera littoralise2herbivore
- Outcome
- effects than Si on various plant traitse0
- Direction
- much strongere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“herbivory predominantly exerts much stronger effects than Si on various plant traits”
e1“Medicago truncatula plants”
e2“Spodoptera littoralis”
Claim · model-written summary
The authors inferred a need for induced defense against herbivory.
- Taxon
- Medicago truncatulaMedicago truncatulae1
- Outcome
- respond to herbivory by induced defence strategiese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“pointing to a necessity to respond to herbivory by induced defence strategies”
e1“Medicago truncatula plants”
The same questions in other papers
silicon atom · growth · Medicago truncatula (barrel medic)Results agree
1 paper in the same direction as this paper
- no effect
Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.