Comparative study of

biomechanical properties in

ethnobotanically useful plants.

Francisca D. Herrera and Dr. Curtis Clark

McNair Scholars Program

Biological Sciences Department

California State Polytechnic University, Pomona

background

• biomechanics

– the study of the mechanics of biological

materials and structures

• ethnobotany

– the study of the historical and/or traditional uses

of plants by humans

• medicinal and nutritional

• mechanical

purpose

to explore the usefulness of biomechanics in

investigating the ethnobotany of early

southern California indigenous cultures

overview

Pluchea sericea vs. Salix exigua

- structurally similar

- different uses

Typha sp. vs. Scirpus sp.

- structurally different

- similar uses

Juncus textilis vs. Juncus mexicanus

- structurally similar

- similar uses

sub-study 1 sub-study 2 sub-study 3

objectives

1. analyze the biomechanical performance of

the selected species

2. determine differences between the

compared species

3. predict the biomechanical reasons for a

particular ethnobotanical use

hypothesis

Ho: Regardless of differences in ethnobotanical

use, there are no differences in the

biomechanical properties between compared

organisms in each case study.

study organisms

Pluchea sericea

‘Arrow-weed’

Salix exigua

‘Sandbar Willow’

sub-study 1 sub-study 2 sub-study 3

ethnobotany

P. sericea ‘Arrow-weed’

arrowshafts

S. exigua ‘Sandbar Willow’

frameworks

sub-study 1 sub-study 2 sub-study 3

biomechanicssub-study 1 sub-study 2 sub-study 3

flexibility and breakage point

kg

stemdiameter

15cm

1/2 pt

1.0

m.

study organisms

Juncus textilis Juncus mexicanus

sub-study 1 sub-study 2 sub-study 3

ethnobotany

Juncus spp.

basketry

sub-study 1 sub-study 2 sub-study 3

biomechanics

tensile strength

30cm

stem

diameter

sub-study 1 sub-study 2 sub-study 3

study organisms

Typha sp.

‘Cattail’

Scirpus sp.

‘Bulrush’

sub-study 1 sub-study 2 sub-study 3

ethnobotanysub-study 1 sub-study 2 sub-study 3

Typha sp. ‘Cattail’ Scirpus sp. ‘Bulrush’

mats and thatch

biomechanics

diameter (mm) stemwater drop

sub-study 1 sub-study 2 sub-study 3

hydrophobicity

analyses

1. anatomical comparisons• light microscopy

2. statistical analysis• program: SPSS

• tests: regression & two-factor ANCOVA

- Dependent Variable: biomechanical performance

- Fixed Factors: species and condition (fresh/dry)

- Covariates: height and diameter

resultssub-study 1 sub-study 2 sub-study 3

P. sericea

‘Arrow-weed’

S. exigua

‘Sandbar Willow’

results

flexibility –

arrow-weed is less flexible than willowit takes more weight to deflect arrow-weed to the 15cm point,

holding constant the effect of height and diameter

breakage –

arrow-weed breaks more easily than willow(flexibility is a predictor of breakage)

sub-study 1 sub-study 2 sub-study 3

resultssub-study 1 sub-study 2 sub-study 3

Juncus textilis Juncus mexicanus

results

tensile strength –

Juncus mexicanus is stronger than

Juncus textilis

sub-study 1 sub-study 2 sub-study 3

resultssub-study 1 sub-study 2 sub-study 3

Typha sp.

‘Cattail’

Scirpus sp.

‘Bulrush’

resultssub-study 1 sub-study 2 sub-study 3

tensile strength –

there was no difference between Scirpus and

Typha

hydrophobicity –

there was no difference between Scirpus and

Typha

discussion

arrow-shafts & dwelling frameworks –

Our null hypothesis was rejected.

Dry arrow-weed is stiffer and fresh willow is

more flexible.

Results supported the preference of these

biomechanical properties in their

ethnobotanical use.

sub-study 1 sub-study 2 sub-study 3

discussion

basketry –

Our null hypothesis was rejected.

While there are structural differences,

J. mexicanus is the stronger species.

The wet/dry condition is not a good predictor of

tensile strength.

Results neither denied nor confirmed the

desirability of tensile strength in basketry.

sub-study 1 sub-study 2 sub-study 3

discussion

mats & thatching –

Our null hypothesis was not rejected.

No difference may account for overlap in use between the species.

Results indicate that tensile strength and hydrophobicity may have been desirable

properties in mats and thatching

sub-study 1 sub-study 2 sub-study 3

acknowledgements

• Dr. Curtis J. Clark, Professor of Biology

• McNair Scholars Program, Cal Poly Pomona

• BioTrek

• Tongva/Gabrielino of San Gabriel

• Lorene Sisquoc, Apache/Cahuilla

• Dr. Pfeiffer and UC Davis

Species were selected based on the following criteria:

• native southern California plants

• historical ethnobotanical use by southern California indigenous

cultures

• availability of biological material from a common garden

• structural similarities among compared organisms

• feasibility of biomechanical property being measured

Selection of Study Organisms

Regressions performed:

• height vs diameter – to look at usefulness as covariates

• height and/or diameter vs biomechanical property – to look at relationship between covariates and dependent variables

Other analyses:

• species vs condition interaction – to determine a difference in the way species respond mechanically in fresh and dry conditions

• ANCOVA – to test for difference in mechanical performance between species

Development of Statistical Model

Regression Analyses

Arrow-weed & sandbar willow comparison:

height vs diameter

breakage vs deflection

height/diameter vs deflection

height/diameter vs breakage

Comparison of rushes:

height vs diameter

height/diameter vs tensile strength

Bulrush & cattail comparison:

height vs diameter

height/diameter vs tensile strength

ANCOVA Results

Tests of Betw een-Subjects Effects

Dependent Variable: weight in kg to 15cm deflection pt

98.118a 5 19.624 48.670 .000

17.725 1 17.725 43.962 .000

1.772 1 1.772 4.395 .044

40.409 1 40.409 100.222 .000

2.267 1 2.267 5.623 .024

11.715 1 11.715 29.055 .000

5.256 1 5.256 13.036 .001

13.709 34 .403

220.233 40

111.827 39

Source

Corrected Model

Intercept

stem_ht

stem_d

species

condn

species * condn

Error

Total

Corrected Total

Type III Sum

of Squares df Mean Square F Sig.

R Squared = .877 (Adjusted R Squared = .859)a.

arrow-weed vs sandbar willow:

Tests of Betw een-Subjects Effects

Dependent Variable: weight in kg to break stem

195.629a 4 48.907 10.125 .000

12.571 1 12.571 2.603 .116

23.864 1 23.864 4.941 .033

.979 1 .979 .203 .655

11.651 1 11.651 2.412 .129

59.505 1 59.505 12.319 .001

169.061 35 4.830

2616.190 40

364.690 39

Source

Corrected Model

Intercept

species

condn

stem_ht

avg_d

Error

Total

Corrected Total

Type III Sum

of Squares df Mean Square F Sig.

R Squared = .536 (Adjusted R Squared = .483)a.

ANCOVA Results

J. mexicanus vs J. textilis:

ANCOVA Results

Tests of Betw een-Subjects Effects

Dependent Variable: tensile strength

327.318a 2 163.659 34.320 .000

6.193 1 6.193 1.299 .270

9.617 1 9.617 2.017 .174

46.818 1 46.818 9.818 .006

81.067 17 4.769

2265.050 20

408.385 19

Source

Corrected Model

Intercept

species

avg_d

Error

Total

Corrected Total

Type III Sum

of Squares df Mean Square F Sig.

R Squared = .801 (Adjusted R Squared = .778)a.

cattail vs bulrush:

Type III Tests of Fixed Effectsa

1 58 3703.571 .000

1 58 .403 .528

Source

Intercept

species

Numerator df

Denominator

df F Sig.

Dependent Variable: H2O_diam.a.

ANCOVA Results

cattail vs bulrush (cont’d):