Abstract
The elastic modulus E, flexural rigidity EI, static loading P, and volume fractions V of tissues of the aerial portions of Psilotum nudum are examined in terms of two Voigt models: 1) total elastic modulus ET of a branch element is considered the additive property of the elastic modulus of tissues times their respective volume fraction, i.e., ET = (EV), + (EV)2 + … (EV)n, and 2) ET is considered the product of the elastic modulus of cell walls and the apoplastic volume fraction, i.e., ET = EcwVa. The parameters EI and P, together with the length (l) of each branch element are combined into a dimensionless ratio, Pl2/EI (the load parameter L), to describe the relationship between static loading (Pl2) and the ability to sustain loading (EI). The load parameter of branch elements was found to decrease as the level of branching within aerial portions of this race of Psilotum was ascended. The magnitude of P also decreased acropetally. However, the decrease in L is primarily due to a disproportionate decrease in EI. The load parameter of the basalmost branch of aerial portions is smaller for larger aerial portions of this race of P. nudum. Thus, larger specimens are subtended by more rigid branch elements than smaller aerial portions. The Voigt models provide satisfactory approximations of the data from this race Psilotum and indicate that the principal load supporting tissues are the cortical sclerenchyma and other lignified tissues in older (lower branch elements). The mechanics of the three dimensional branching of P. nudum is extended to consider the aerial portions of some early Paleozoic vascular sporophytes (Algaophyton, Rhynia). Analyses indicate that biomechanical speculation about these fossils is potentially flawed by the ambiguity of anatomical data.
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Claims 8
Claim · model-written summary
The load parameter of branch elements decreased as the level of branching within aerial portions ascended.
- Taxon
- Psilotum nudum
_-_DPLA_-_4ac2674d6375a60a482c98ead952718b.jpg?width=60)
Psilotum nudumt0 - Organ / stage
- aerial portionse1
- Outcome
- load parameter of branch elementse1
- Direction
- decreasee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
_-_DPLA_-_4ac2674d6375a60a482c98ead952718b.jpg?width=500)
Verbatim
t0“Biomechanics of Psilotum nudum”
e1“The load parameter of branch elements was found to decrease as the level of branching within aerial portions of this race of Psilotum was ascended”
Claim · model-written summary
The magnitude of static loading P decreased acropetally.
- Taxon
- Psilotum nudumPsilotum nudumt0
- Outcome
- magnitude of Pe2
- Direction
- decreasede2
- Qualifier
- acropetallye2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Biomechanics of Psilotum nudum”
e2“The magnitude of P also decreased acropetally”
Claim · model-written summary
The decrease in the load parameter L is primarily due to a disproportionate decrease in flexural rigidity EI.
- Taxon
- Psilotum nudumPsilotum nudumt0
- Outcome
- decrease in Le3
- Qualifier
- a disproportionate decrease in EIe3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Biomechanics of Psilotum nudum”
e3“However, the decrease in L is primarily due to a disproportionate decrease in EI”
Claim · model-written summary
The load parameter of the basalmost branch is smaller in larger aerial portions.
- Taxon
- Psilotum nudumPsilotum nudumt0
- Organ / stage
- basalmost branch of aerial portionse4
- Outcome
- load parameter of the basalmost branche4
- Direction
- smallere4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Biomechanics of Psilotum nudum”
e4“The load parameter of the basalmost branch of aerial portions is smaller for larger aerial portions of this race of P. nudum”
Claim · model-written summary
Larger specimens have more rigid branch elements than smaller aerial portions.
- Taxon
- Psilotum nudumPsilotum nudumt0
- Outcome
- rigid branch elementse5
- Direction
- moree5
- Comparator
- smaller aerial portionse5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Biomechanics of Psilotum nudum”
e5“Thus, larger specimens are subtended by more rigid branch elements than smaller aerial portions”
Claim · model-written summary
The Voigt models gave satisfactory approximations of the Psilotum data.
- Taxon
- Psilotum nudumPsilotum nudumt0
- Outcome
- satisfactory approximations of the datae6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Biomechanics of Psilotum nudum”
e6“The Voigt models provide satisfactory approximations of the data from this race Psilotum”
Claim · model-written summary
The principal load-supporting tissues are cortical sclerenchyma and other lignified tissues in older lower branch elements.
- Taxon
- Psilotum nudumPsilotum nudumt0
- Organ / stage
- cortical sclerenchyma and other lignified tissuese7
- Outcome
- principal load supporting tissuese7
- Qualifier
- in older (lower branch elements)e7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Biomechanics of Psilotum nudum”
e7“indicate that the principal load supporting tissues are the cortical sclerenchyma and other lignified tissues in older (lower branch elements)”
Claim · model-written summary
Biomechanical speculation about these early Paleozoic fossils is potentially flawed by ambiguous anatomical data.
Verbatim
t1“Some Early Paleozoic Vascular Sporophytes”
e1“Analyses indicate that biomechanical speculation about these fossils is potentially flawed by the ambiguity of anatomical data”