Stomatal adjustment to water transport capacity



Stomatal and hydraulic conductance in growing sugarcane: stomatal adjustment to water transport capacity.

by Meinzer F. C., Grantz D. A. (1990)

Hawaiian Sugar Planters’ Association, P.O. Box 1057, Aiea, HI 96701, U.S.A.

in Plant Cell Environ 13: 383–388 – DOI: 10.1111/j.1365-3040.1990.tb02142.x –

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Stomatal conductance per unit leaf area in well-irrigated field- and greenhouse-grown sugarcane increased with leaf area up to 0.2 m2 plant 1, then declined so that maximum transpiration per plant tended to saturate rather than increase linearly with further increase in leaf area.

Conductance to liquid water transport exhibited parallel changes with plant size. This coordination of vapour phase and liquid phase conductances resulted in a balance between water loss and water transport capacity, maintaining leaf water status remarkably constant over a wide range of plant size and growing conditions.

The changes in stomatal conductance were not related to plant or leaf age. Partial defoliation caused rapid increases in stomatal conductance, to re-establish the original relationship with remaining leaf area. Similarly, pruning of roots caused rapid reductions in stomatal conductance, which maintained or improved leaf water status.

These results suggest that sugarcane stomata adjusted to the ratio of total hydraulic conductance to total transpiring leaf area. This could be mediated by root metabolites in the transpiration stream, whose delivery per unit leaf area would be a function of the relative magnitudes of root system size, transpiration rate and leaf area.

Malic and citric acids provide much of the counter ion for the K(+) taken up during stomatal opening



Organic-acid and potassium accumulation in guard cells during stomatal opening

Outlaw W. H., Lowry O. H. (1977)

Department of Pharmacology, Washington University School of Medicine, St. Louis, Missouri 63110.

in Proceedings of the National Academy of Sciences, USA 74: 44344438 -PMID: 16592449 PMCID: PMC431957 – 

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Leaflets of Vicia faba L. with either open or closed stomata were quick-frozen and freeze-dried. Individual guard cell pairs and pure samples of palisade parenchyma, spongy parenchyma, and epidermis lacking guard cells were dissected from the leaflets, weighed, and assayed for organic acids or K(+).K(+) was measured by a new enzymatic method.

In guard cells of open stomata, as compared to closed stomata, K(+) was 2- to 4-fold higher, malic acid 6-fold higher, and citric acid 3-fold higher. Both aspartic and glutamic acids were also higher, but the amounts present were low compared to malic and citric acids.

Isocitric acid was significantly higher in one experiment, but not in another. Glyceric acid was not increased. Succinic acid was too low to detect by the method used; but in guard cells of open stomata the concentration must have been less than 2% of that of malic acid. Malic acid was higher in the palisade parenchyma from the leaflet with open stomata. The ion balance shows that malic and citric acids provide much of the counter ion for the K(+) taken up during stomatal opening.

The vacuole in differentiating stomata undergoes two major changes in morphology



The vacuole system in stomatal cells of Allium  Vacuole movements and changes in morphology in differentiating cells as revealed by epifluorescence, video and electron-microscopy.

by Palevitz B. A., O’Kane D. J., Korbes R. E., Raikhel N. V. (1981)

in Protoplasma 109: 2355.- 

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The development of autofluorescent vacuoles in the stomatal cells of Allium cepa and A. vineale was investigated using fluorescence microscopy of live cells, low light level television, cytochemistry and electron microscopy.

During cell differentiation, the vacuole undergoes two major changes in morphology. In an intermediate form, it consists of a reticulum or network of interlinked tubules and small chambers. The network is formed from globular cisternae in very young GMCs and is maintained as a reticulum until it is transformed back into a globular form later in the differentiation of guard cells.

The network thus remains intact through the course of one cell division. During its existence, the reticulum undergoes complex movements and rearrangements. The significance of these changes in the vacuole is discussed in terms of vacuole ontogeny and function and the mechanisms that control motility in plant cells.

Plasmodesmata and the mechanism of stomatal movements.



Electron microscopic evidence for plasmodesmata in dicotyledonous guard cells.

by Pallas J. E. Jr., Mollenhauer H. H. (1972)

in Sci. 175, 1275–1276 -DOI: 10.1126/science.175.4027.1275 –

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In Nicotianna tobaccum and Vicia faba leaves, plasmodesmata were observed by electron microscopy in walls between sister guard cells and walls between guard and epidermal cells.

The latter were found primarily in pit fields of anticlinal walls and showed considerable complexity as evidenced by branching. Cytologically, the plasmodesmata appear functional in operative guard cells and should be considered in the mechanism of stomatal movements.

Stomatal dimensions and resistance to diffusion



Stomatal dimensions and resistance to diffusion

by Parlange J.‐Y., Waggoner P. E. (1970)

Jean-Yves Parlange, Engineering and Applied Science, Yale University, New Haven, Connecticut.

Paul E. Waggoner

in Plant Physiology 46,337–342.  –

CrossRefPubMedCAS[PMC free article] [PubMed] –


In the past, relations of diffusive resistance to stomatal geometry have concerned circular pores or pores that are replaced by equivalent circles of the same area.

We calculated the resistance for general shapes that include the realistic slit. The resistance comprises two terms. The first is an outer resistance that depends only on ventilation and leaf geometry and is independent of stomata. The second is an inner resistance and is a function of stomatal interference and of stomatal geometry only.

If interstomatal spacing is at least three times stomatal length, interstomatal interference is negligible. The inner resistance can then be calculated by adding the resistance of the two ends and the throat of each stoma.

In the case of an elongated stoma, the part of the diffusive resistance per square centimeter determined by stomatal geometry is [Formula: see text] where a, b, d, and n are the semilength, semiwidth, depth, and density of the stomata, and D is the diffusivity.

This is the familiar Brown and Escombe result applied to slits.


Daily changes in stomatal aperture


Photo credit: Google

Commelina cyanea (Commelina diffusa)

Daily changes in stomatal aperture and in carbohydrates and malate within epidermis and mesophyll of leaves of Commelina cyanea and Vicia faba.

by Pearson C. J. (1973)

in Aust. J. Biol. Sci. 26, 1035–1044 – –

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Stomatal apertures and methanol-, water-, and hydrochloric acid-soluble carbohydrates and malate were measured in the epidermis, mesophyll, and midvein of leaves of C. cyanea R. Br. and V. [aba L. over a period of 26 hr in one experiment and over 9 hr during the photoperiod in a second experiment.

A novel chloride channel activated by CDPK in stomata



A novel chloride channel in Vicia faba guard cell vacuoles activated by the serine/threonine kinase, CDPK.

by Pei Z.-M., Ward J. M., Harper J. F., Schroeder J. I. (1996)

Department of Biology and Center for Molecular Genetics, University of California, San Diego, La Jolla 92093-0116, USA.

in EMBO Journal 15, 65646574 – PMID: 8978683 PMCID: PMC452481 –

PubMedCAS , ISIMedline


Calcium-Dependent Protein Kinases (CDPKs) in higher plants contain a C-terminal calmodulin-like regulatory domain. Little is known regarding physiological CDPK targets. Both kinase activity and multiple Ca2+-dependent signaling pathways have been implicated in the control of stomatal guard cell movements.

To determine whether CDPK or other protein kinases could have a role in guard cell signaling, purified and recombinant kinases were applied to Vicia faba guard cell vacuoles during patch-clamp experiments. CDPK activated novel vacuolar chloride (VCL) and malate conductances in guard cells. Activation was dependent on both Ca2+ and ATP. Furthermore, VCL activation occurred in the absence of Ca2+ using a Ca2+-independent, constitutively active, CDPK* mutant.

Protein kinase A showed weaker activation (22% as compared with CDPK). Current reversals in whole vacuole recordings shifted with the Nernst potential for Cl-and vanished in glutamate.

Single channel recordings showed a CDPK-activated 34 +/- 5 pS Cl- channel. VCL channels were activated at physiological potentials enabling Cl- uptake into vacuoles. VCL channels may provide a previously unidentified, but necessary, pathway for anion uptake into vacuoles required for stomatal opening.

CDPK-activated VCL currents were also observed in red beet vacuoles suggesting that these channels may provide a more general mechanism for kinase-dependent anion uptake.