Abstract
Abstract Soil amendment with Silicon (Si) can increase plant resistance against insect herbivores, but the underlying mechanisms remain unclear. The mechanical resistance hypothesis ( MRH ) states that Si accumulated in epidermal cells directly and passively protects against herbivores by creating a mechanical barrier. The physiological resistance hypothesis ( PRH ) states that Si enhances resistance by activating plant biochemical and physiological processes. We tested both hypotheses by manipulating Si fertilization of the Si non‐accumulator collard, B rassica oleracea L. cv. acephala ( B rassicaceae). Then, we assessed functional and ultrastructural plant responses and the developmental and reproductive performance of the leaf‐chewing larvae of the diamondback moth, P lutella xylostella L. ( L epidoptera: P lutellidae), and the sap‐sucking cabbage aphid, B revicoryne brassicae L. ( H emiptera: A phididae). There was a 20% increase in leaf Si content. Silicon deposition in epidermal cells was identified by confocal microscopy and directly coincided with lower performance of P . xylostella , but did not affect B . brassicae . On the other hand, we found no unequivocal evidence that Si‐mediated changes in primary and secondary metabolism improved plant resistance against the insects. Negative mechanical effects of Si on the insects may have masked beneficial effects of increased water, nitrogen, and mineral contents in Si‐treated collards. Silicon did not change leaf contents of hemicellulose, cellulose, and lignin. Although Si‐mediated increases in leaf glucosinolates ( GLS ) correlated with lower larval performance and higher oviposition preference of P . xylostella , both P . xylostella and B . brassicae are highly specialized in overcoming such secondary metabolites. Thus, mechanical resistance may have impaired P . xylostella , rather than the Si‐mediated increase in GLS . We suggest that the PRH may depend on the degree of insect feeding specialization, so that toxic Si‐mediated defenses may be more efficient against unadapted polyphagous herbivores. For them, a toxic barrier may be added to the mechanical resistance.
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Claims 11
Claim · model-written summary
Silicon treatment increased collard leaf silicon content by 20%.
Not reportedComparator
Verbatim
e0“There was a 20% increase in leaf Si content”
e1“Si fertilization of the Si non‐accumulator collard”
Claim · model-written summary
Silicon deposition was detected in epidermal cells.
Verbatim
e0“Silicon deposition in epidermal cells was identified by confocal microscopy”
t0“collard”
Claim · model-written summary
Silicon deposition coincided with lower diamondback moth performance.
Verbatim
e0“Silicon deposition in epidermal cells was identified by confocal microscopy and directly coincided with lower performance of P . xylostella”
t0“collard”
Claim · model-written summary
Silicon deposition did not affect cabbage aphid performance.
- Taxon
- collardt0
- Treatment
- Silicone1
- Interactor
- B . brassicaee0herbivore
- Outcome
- B . brassicaee0
- Direction
- did not affecte0
Not reportedComparator
Verbatim
e0“but did not affect B . brassicae”
e1“Silicon deposition in epidermal cells was identified by confocal microscopy”
t0“collard”
Claim · model-written summary
No unequivocal evidence supported metabolic changes improving insect resistance.
Not reportedDirection
Verbatim
e0“no unequivocal evidence that Si‐mediated changes in primary and secondary metabolism improved plant resistance against the insects”
t0“collard”
Claim · model-written summary
Silicon increased water, nitrogen and mineral contents in collard leaves.
- Taxon
- collards
Brassica oleracea var. viridise0 - Treatment
- Si‐treatede0
- Outcome
- water, nitrogen, and mineral contentse0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increased water, nitrogen, and mineral contents in Si‐treated collards”
Claim · model-written summary
Silicon did not change hemicellulose, cellulose and lignin content.
- Taxon
- collardt0
- Treatment
- Silicone0
- Outcome
- leaf contents of hemicellulose, cellulose, and lignine0
- Direction
- did not changee0
Not reportedComparator
Verbatim
e0“Silicon did not change leaf contents of hemicellulose, cellulose, and lignin”
t0“collard”
Claim · model-written summary
Silicon increased leaf glucosinolates.
Not reportedComparator
Verbatim
e0“Si‐mediated increases in leaf glucosinolates ( GLS )”
t0“collard”
Claim · model-written summary
Increased leaf glucosinolates correlated with lower diamondback moth larval performance.
Verbatim
e0“increases in leaf glucosinolates ( GLS ) correlated with lower larval performance and higher oviposition preference of P . xylostella”
t0“collard”
Claim · model-written summary
Increased leaf glucosinolates correlated with higher diamondback moth oviposition preference.
Verbatim
e0“increases in leaf glucosinolates ( GLS ) correlated with lower larval performance and higher oviposition preference of P . xylostella”
t0“collard”
Claim · model-written summary
The authors suggested mechanical silicon resistance impaired diamondback moth larvae.
Verbatim
e0“mechanical resistance may have impaired P . xylostella , rather than the Si‐mediated increase in GLS”
t0“collard”
The same questions in other papers
silicon atom · nutrient: content · Brassica oleracea (wild cabbage)Results agree
4 papers in the same direction as this paper
- positive
- positive
- positive
1 paper more in this group
See all 5 papers →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.