Abstract
It has long been accepted that differential radial thickening of guard cells plays an important role in the turgor-driven shape changes required for stomatal pore opening to occur [1-4]. This textbook description derives from an original interpretation of structure rather than measurement of mechanical properties. Here we show, using atomic force microscopy, that although mature guard cells display a radial gradient of stiffness, this is not present in immature guard cells, yet young stomata show a normal opening response. Finite element modeling supports the experimental observation that radial stiffening plays a very limited role in stomatal opening. In addition, our analysis reveals an unexpected stiffening of the polar regions of the stomata complexes, both in Arabidopsis and other plants, suggesting a widespread occurrence. Combined experimental data (analysis of guard cell wall epitopes and treatment of tissue with cell wall digesting enzymes, coupled with bioassay of guard cell function) plus modeling lead us to propose that polar stiffening reflects a mechanical, pectin-based pinning down of the guard cell ends, which restricts increase of stomatal complex length during opening. This is predicted to lead to an improved response sensitivity of stomatal aperture movement with respect to change of turgor pressure. Our results provide new insight into the mechanics of stomatal function, both negating an established view of the importance of radial thickening and providing evidence for a significant role for polar stiffening. Improved stomatal performance via altered cell-wall-mediated mechanics is likely to be of evolutionary and agronomic significance.
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Claims 6
Claim · model-written summary
Mature guard cells had a radial stiffness gradient, whereas immature guard cells did not.
- Taxon
- Arabidopsis
Arabidopsise1 - Organ / stage
- guard cellse0
- Outcome
- radial gradient of stiffnesse0
- Comparator
- immature guard cellse0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“mature guard cells display a radial gradient of stiffness, this is not present in immature guard cells”
e1“both in Arabidopsis and other plants”
Claim · model-written summary
Young stomata opened normally despite lacking the radial stiffness gradient.
- Taxon
- ArabidopsisArabidopsise1
- Organ / stage
- young stomatae0
- Outcome
- normal opening responsee0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“this is not present in immature guard cells, yet young stomata show a normal opening response”
e1“both in Arabidopsis and other plants”
Claim · model-written summary
Finite-element modeling indicated that radial stiffening plays a very limited role in stomatal opening.
- Taxon
- ArabidopsisArabidopsise1
- Outcome
- stomatal openinge0
- Qualifier
- radial stiffening plays a very limited rolee0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Finite element modeling supports the experimental observation that radial stiffening plays a very limited role in stomatal opening.”
e1“both in Arabidopsis and other plants”
Claim · model-written summary
Stomatal polar regions were stiffened in Arabidopsis and other plants.
- Taxon
- ArabidopsisArabidopsise0
- Organ / stage
- polar regions of the stomata complexese0
- Outcome
- stiffeninge0
- Direction
- stiffeninge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“an unexpected stiffening of the polar regions of the stomata complexes, both in Arabidopsis and other plants”
Claim · model-written summary
The authors propose that pectin-based polar pinning restricts stomatal complex lengthening during opening.
- Taxon
- ArabidopsisArabidopsise1
- Outcome
- increase of stomatal complex length during openinge0
- Direction
- restrictse0
- Qualifier
- pectin-based pinning down of the guard cell endse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“polar stiffening reflects a mechanical, pectin-based pinning down of the guard cell ends, which restricts increase of stomatal complex length during opening”
e1“both in Arabidopsis and other plants”
Claim · model-written summary
The proposed polar pinning is predicted to improve stomatal aperture sensitivity to turgor change.
- Taxon
- ArabidopsisArabidopsise1
- Outcome
- response sensitivity of stomatal aperture movemente0
- Direction
- improvede0
- Qualifier
- polar stiffening reflects a mechanical, pectin-based pinning downe2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This is predicted to lead to an improved response sensitivity of stomatal aperture movement with respect to change of turgor pressure.”
e1“both in Arabidopsis and other plants”
e2“polar stiffening reflects a mechanical, pectin-based pinning down”