Abstract
Abstract Isolated cuticular wax, obtained from barley leaves, was mixed with 14 Clabelled organic chemicals including aromatic pesticides and long‐chain linear alkanes, alcohols and acids. These mixtures were reconstituted from the melt and labelled chemicals were desorbed from the wax by immersing the wax samples in aqueous phospholipid suspensions. Diffusion coefficients ( D ) of radiolabelled test compounds in the wax were derived from desorption kinetics. Diffusion coefficients ranged from 10 −17 to 10 −22 m 2 s −1 and decreased rapidly with increasing molar volumes of solutes. However, size selectivity of D was much more pronounced with the linear, long‐chain molecules than with the aromatic compounds. It is argued that the two different groups of chemicals (compounds occurring naturally in cuticular waxes vs pesticide molecules) were trapped in different fractions of wax during crystallization from the melt. The normal long‐chain aliphatic compounds appear to be incorporated into the crystalline fraction of the wax, while the cyclic pesticide molecules are confined to the solid amorphous regions. Our data indicate that constituents of cuticular waxes are not immobile. In fact, relatively small linear aliphatic molecules have mobilities that do not differ too much from those of cyclic pesticides. However, the pronounced size selectivity of diffusivities of long‐chain aliphatic compounds causes a rapid decrease in D with increasing chain length. The value of D of hexadecanoic acid was 3.81 × 10 −18 m 2 s −1 while that of dotriacontane was only 4.07 × 10 −22 m 2 s −1 . Thus, increasing the carbon number by a factor of two resulted in a decrease in mobility by almost four orders of magnitude. Diffusivities of selected pesticide molecules in reconstituted wax were compared with permeances measured using intact barley leaves and were found to be in satisfactory agreement.
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Claims 12
Claim · model-written summary
Diffusion coefficients in barley wax ranged from 10 −17 to 10 −22 m 2 s −1.
- Taxon
- barley leaves
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Hordeum vulgaret0 - Outcome
- Diffusion coefficientse0
- Value
- 10 −17 to 10 −22 m 2 s −1e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
e0“Diffusion coefficients ranged from 10 −17 to 10 −22 m 2 s −1”
t0“barley leaves”
Claim · model-written summary
Diffusion coefficients declined rapidly as solute molar volume increased.
- Taxon
- barley leavesHordeum vulgaret0
- Compound
- solutese0
- Outcome
- Diffusion coefficientse0
- Direction
- decreased rapidlye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Diffusion coefficients ranged from 10 −17 to 10 −22 m 2 s −1 and decreased rapidly with increasing molar volumes of solutes”
t0“barley leaves”
Claim · model-written summary
Size selectivity was stronger for long-chain linear molecules than aromatic compounds.
- Taxon
- barley leavesHordeum vulgaret0
- Outcome
- size selectivity of De0
- Direction
- much more pronouncede0
- Comparator
- aromatic compoundse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“size selectivity of D was much more pronounced with the linear, long‐chain molecules than with the aromatic compounds”
t0“barley leaves”
Claim · model-written summary
Authors infer that natural wax compounds and pesticides became trapped in different wax fractions.
- Taxon
- barley leavesHordeum vulgaret0
- Outcome
- trapped in different fractions of waxe0
- Qualifier
- during crystallization from the melte0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“two different groups of chemicals (compounds occurring naturally in cuticular waxes vs pesticide molecules) were trapped in different fractions of wax during crystallization from the melt”
t0“barley leaves”
Claim · model-written summary
Long-chain aliphatic compounds appeared incorporated in crystalline wax.
- Taxon
- barley leavesHordeum vulgaret0
- Outcome
- incorporated into the crystalline fraction of the waxe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“normal long‐chain aliphatic compounds appear to be incorporated into the crystalline fraction of the wax”
t0“barley leaves”
Claim · model-written summary
Cyclic pesticide molecules appeared confined to amorphous wax regions.
- Taxon
- barley leavesHordeum vulgaret0
- Outcome
- confined to the solid amorphous regionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“cyclic pesticide molecules are confined to the solid amorphous regions”
t0“barley leaves”
Claim · model-written summary
Wax constituents were mobile.
- Taxon
- barley leavesHordeum vulgaret0
- Outcome
- not immobilee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“constituents of cuticular waxes are not immobile”
t0“barley leaves”
Claim · model-written summary
Small linear aliphatic molecules had mobilities similar to cyclic pesticides.
- Taxon
- barley leavesHordeum vulgaret0
- Outcome
- mobilitiese0
- Direction
- do not differ too muche0
- Comparator
- cyclic pesticidese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“relatively small linear aliphatic molecules have mobilities that do not differ too much from those of cyclic pesticides”
t0“barley leaves”
Claim · model-written summary
Hexadecanoic acid had a diffusion coefficient of 3.81 × 10 −18 m 2 s −1.
- Taxon
- barley leavesHordeum vulgaret0
- Outcome
- D of hexadecanoic acide0
- Value
- 3.81 × 10 −18 m 2 s −1e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The value of D of hexadecanoic acid was 3.81 × 10 −18 m 2 s −1”
t0“barley leaves”
Claim · model-written summary
Dotriacontane had a diffusion coefficient of 4.07 × 10 −22 m 2 s −1.
- Taxon
- barley leavesHordeum vulgaret0
- Outcome
- dotriacontanee0
- Direction
- onlye0
- Value
- 4.07 × 10 −22 m 2 s −1e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“that of dotriacontane was only 4.07 × 10 −22 m 2 s −1”
t0“barley leaves”
Claim · model-written summary
Doubling carbon number reduced mobility almost four orders of magnitude.
- Taxon
- barley leavesHordeum vulgaret0
- Treatment
- increasing the carbon number by a factor of twoe0
- Outcome
- mobilitye0
- Direction
- decreasee0
- Value
- almost four orders of magnitudee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increasing the carbon number by a factor of two resulted in a decrease in mobility by almost four orders of magnitude”
t0“barley leaves”
Claim · model-written summary
Pesticide diffusivities in reconstituted wax agreed satisfactorily with permeances of intact barley leaves.
- Taxon
- barley leavesHordeum vulgaree0
- Outcome
- Diffusivities of selected pesticide molecules in reconstituted waxe0
- Direction
- satisfactory agreemente0
- Comparator
- permeances measured using intact barley leavese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Diffusivities of selected pesticide molecules in reconstituted wax were compared with permeances measured using intact barley leaves and were found to be in satisfactory agreement”