Abstract
BACKGROUND AND AIMS: Plants in open, uncrowded habitats typically have relatively short stems with many branches, whereas plants in crowded habitats grow taller and more slender at the expense of mechanical stability. There seems to be a trade-off between height growth and mechanical stability, and this study addresses how stand density influences stem extension and consequently plant safety margins against mechanical failure. METHODS: Xanthium canadense plants were grown either solitarily (S-plants) or in a dense stand (D-plants) until flowering. Internode dimensions and mechanical properties were measured at the metamer level, and the critical buckling height beyond which the plant elastically buckles under its own weight and the maximum lateral wind force the plant can withstand were calculated. KEY RESULTS: Internodes were longer in D- than S-plants, but basal diameter did not differ significantly. Relative growth rates of internode length and diameter were negatively correlated to the volumetric solid fraction of the internode. Internode dry mass density was higher in S- than D-plants. Young's modulus of elasticity and the breaking stress were higher in lower metamers, and in D- than in S-plants. Within a stand, however, both moduli were positively related to dry mass density. The buckling safety factor, a ratio of critical buckling height to actual height, was higher in S- than in D-plants. D-plants were found to be approaching the limiting value 1. Lateral wind force resistance was higher in S- than in D-plants, and increased with growth in S-plants. CONCLUSIONS: Critical buckling height increased with height growth due mainly to an increase in stem stiffness and diameter and a reduction in crown/stem mass ratio. Lateral wind force resistance was enhanced due to increased tissue strength and diameter. The increase in tissue stiffness and strength with height growth plays a crucial role in maintaining a safety margin against mechanical failure in herbaceous species that lack the capacity for secondary growth.
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Claims 14
Claim · model-written summary
Internodes were longer in dense-stand Xanthium canadense plants than in solitary plants.
- Taxon
- Xanthium canadense
Xanthium strumarium var. canadensee1 - Organ / stage
- Internodese0
- Treatment
- dense stande1
- Outcome
- Internodese0
- Direction
- longere0
- Comparator
- solitarily (S-plants)e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Internodes were longer in D- than S-plants”
e1“Xanthium canadense plants were grown either solitarily (S-plants) or in a dense stand (D-plants) until flowering”
Claim · model-written summary
Basal diameter did not differ significantly between dense-stand and solitary Xanthium canadense plants.
- Taxon
- Xanthium canadenseXanthium strumarium var. canadensee1
- Treatment
- dense stande1
- Outcome
- basal diametere0
- Direction
- did not differe0
- Comparator
- solitarily (S-plants)e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“basal diameter did not differ significantly”
e1“Xanthium canadense plants were grown either solitarily (S-plants) or in a dense stand (D-plants) until flowering”
Claim · model-written summary
Relative growth rates of internode length and diameter were negatively correlated with the volumetric solid fraction of the internode.
- Taxon
- Xanthium canadenseXanthium strumarium var. canadensee1
- Organ / stage
- internodee0
- Outcome
- Relative growth rates of internode length and diametere0
- Direction
- negatively correlatede0
- Qualifier
- volumetric solid fraction of the internodee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Relative growth rates of internode length and diameter were negatively correlated to the volumetric solid fraction of the internode”
e1“Xanthium canadense plants were grown either solitarily (S-plants) or in a dense stand (D-plants) until flowering”
Claim · model-written summary
Internode dry mass density was higher in solitary than in dense-stand Xanthium canadense plants.
- Taxon
- Xanthium canadenseXanthium strumarium var. canadensee1
- Organ / stage
- Internodee0
- Treatment
- solitarily (S-plants)e1
- Outcome
- Internode dry mass densitye0
- Direction
- highere0
- Comparator
- in a dense stand (D-plants)e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Internode dry mass density was higher in S- than D-plants”
e1“Xanthium canadense plants were grown either solitarily (S-plants) or in a dense stand (D-plants) until flowering”
Claim · model-written summary
Young's modulus of elasticity and breaking stress were higher in dense-stand than in solitary Xanthium canadense plants.
- Taxon
- Xanthium canadenseXanthium strumarium var. canadensee1
- Treatment
- dense stande1
- Outcome
- Young's modulus of elasticity and the breaking stresse0
- Direction
- highere0
- Comparator
- solitarily (S-plants)e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Young's modulus of elasticity and the breaking stress were higher in lower metamers, and in D- than in S-plants”
e1“Xanthium canadense plants were grown either solitarily (S-plants) or in a dense stand (D-plants) until flowering”
Claim · model-written summary
Young's modulus of elasticity and breaking stress were higher in lower metamers of Xanthium canadense.
- Taxon
- Xanthium canadenseXanthium strumarium var. canadensee1
- Organ / stage
- lower metamerse0
- Outcome
- Young's modulus of elasticity and the breaking stresse0
- Direction
- highere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Young's modulus of elasticity and the breaking stress were higher in lower metamers, and in D- than in S-plants”
e1“Xanthium canadense plants were grown either solitarily (S-plants) or in a dense stand (D-plants) until flowering”
Claim · model-written summary
Within a stand, Young's modulus and breaking stress were positively related to internode dry mass density in Xanthium canadense.
- Taxon
- Xanthium canadenseXanthium strumarium var. canadensee1
- Outcome
- both modulie0
- Direction
- positively relatede0
- Qualifier
- dry mass densitye0
- Setting
- Within a stande0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Within a stand, however, both moduli were positively related to dry mass density”
e1“Xanthium canadense plants were grown either solitarily (S-plants) or in a dense stand (D-plants) until flowering”
Claim · model-written summary
The buckling safety factor was higher in solitary than in dense-stand Xanthium canadense plants.
- Taxon
- Xanthium canadenseXanthium strumarium var. canadensee1
- Treatment
- solitarily (S-plants)e1
- Outcome
- buckling safety factore0
- Direction
- highere0
- Comparator
- in a dense stand (D-plants)e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The buckling safety factor, a ratio of critical buckling height to actual height, was higher in S- than in D-plants”
e1“Xanthium canadense plants were grown either solitarily (S-plants) or in a dense stand (D-plants) until flowering”
Claim · model-written summary
Dense-stand Xanthium canadense plants approached the buckling limiting value of 1.
- Taxon
- Xanthium canadenseXanthium strumarium var. canadensee1
- Outcome
- buckling safety factore2
- Qualifier
- D-plants were found to be approaching the limiting value 1e3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Xanthium canadense plants were grown either solitarily (S-plants) or in a dense stand (D-plants) until flowering”
e2“The buckling safety factor, a ratio of critical buckling height to actual height, was higher in S- than in D-plants”
e3“D-plants were found to be approaching the limiting value 1”
Claim · model-written summary
Lateral wind force resistance was higher in solitary than in dense-stand Xanthium canadense plants.
- Taxon
- Xanthium canadenseXanthium strumarium var. canadensee1
- Treatment
- solitarily (S-plants)e1
- Outcome
- Lateral wind force resistancee0
- Direction
- highere0
- Comparator
- in a dense stand (D-plants)e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Lateral wind force resistance was higher in S- than in D-plants, and increased with growth in S-plants”
e1“Xanthium canadense plants were grown either solitarily (S-plants) or in a dense stand (D-plants) until flowering”
Claim · model-written summary
Lateral wind force resistance increased with growth in solitary Xanthium canadense plants.
- Taxon
- Xanthium canadenseXanthium strumarium var. canadensee1
- Outcome
- Lateral wind force resistancee0
- Direction
- increasede0
- Qualifier
- with growth in S-plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Lateral wind force resistance was higher in S- than in D-plants, and increased with growth in S-plants”
e1“Xanthium canadense plants were grown either solitarily (S-plants) or in a dense stand (D-plants) until flowering”
Claim · model-written summary
Critical buckling height increased with height growth, mainly through stem stiffness and diameter and a lower crown/stem mass ratio.
- Taxon
- Xanthium canadenseXanthium strumarium var. canadensee1
- Outcome
- Critical buckling height increasede0
- Qualifier
- due mainly to an increase in stem stiffness and diameter and a reduction in crown/stem mass ratioe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Critical buckling height increased with height growth due mainly to an increase in stem stiffness and diameter and a reduction in crown/stem mass ratio”
e1“Xanthium canadense plants were grown either solitarily (S-plants) or in a dense stand (D-plants) until flowering”
Claim · model-written summary
Lateral wind force resistance was enhanced by increased tissue strength and diameter in Xanthium canadense.
- Taxon
- Xanthium canadenseXanthium strumarium var. canadensee1
- Outcome
- Lateral wind force resistance was enhancede0
- Qualifier
- due to increased tissue strength and diametere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Lateral wind force resistance was enhanced due to increased tissue strength and diameter”
e1“Xanthium canadense plants were grown either solitarily (S-plants) or in a dense stand (D-plants) until flowering”
Claim · model-written summary
Increasing tissue stiffness and strength with height growth plays a role in keeping a safety margin against mechanical failure in Xanthium canadense.
- Taxon
- Xanthium canadenseXanthium strumarium var. canadensee1
- Outcome
- safety margin against mechanical failuree0
- Qualifier
- The increase in tissue stiffness and strength with height growthe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The increase in tissue stiffness and strength with height growth plays a crucial role in maintaining a safety margin against mechanical failure”
e1“Xanthium canadense plants were grown either solitarily (S-plants) or in a dense stand (D-plants) until flowering”