Chloride reduces malate production in epidermis during stomatal opening



Presence of Chloride Reduces Malate Production in Epidermis during Stomatal Opening

by Van Kirk C. A., Raschke K. (1978)

Carol A. Van Kirk, Klaus Raschke,

Michigan State University/Energy Research and Development Administration Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824

in Plant Physiol. 61: 361-364 –


When stomata of isolated epidermis of Vicia faba are allowed to open in the presence of K+ and iminodiacetate (an impermeant zwitterion), malate is formed in the epidermis; the increases in malate content follow a nearly linear relationship with stomatal aperture.

Stomata of leaf sections of V. faba floated on water during opening also exhibit this relationship. When isolated epidermis is offered KC, this relationship is not observed and less malate is detected at comparable stomatal apertures.

The data indicate that Cl-, if present at concentrations ; 10-5 eq liter-‘, can partially satisfy the anion requirement of guard cels of V. faba during stomatal opening. Discrepancies between earler reports on the relative roles Cl- and malate play as counterions for K+ in guard cells of V. faba could now be explained as resulting from variations in the availability of Cl- to guard cells.


Leaf age, ABA content, transpiration and stomatal conductance

Photo credit: Google

Xanthium strumarium


Abscisic acid content, transpiration and stomatal conductance as related to leaf age in plants of Xanthium strumarium L.

by Raschke K., Zeevaart J. A. D. (1976)

Klaus RaschkeJan A. D. Zeevaart,

in Plant Physiol 58: 169-174 – 


Among the four uppermost leaves of greenhouse-grown plants of Xanthium strumarium L. the content of abscisic acid per unit fresh or dry weight was highest in the youngest leaf and decreased gradually with increasing age of the leaves.

Expressed per leaf, the second youngest leaf was richest in ABA; the amount of ABA per leaf declined only slightly as the leaves expanded.

Transpiration and stomatal conductance were negatively correlated with the ABA concentration in the leaves; the youngest leaf lost the least amount of water. This correlation was always very good if the youngest leaf was compared with the older leaves but not always good among the older leaves.

Since stomatal sensitivity to exogenous (±)-ABA was the same in leaves of all four age groups ABA may be in at least two compartments in the leaf, one of which is isolated from the guard cells.

The ability to synthesize ABA in response to wilting or chilling was strongly expressed in young leaves and declined with leaf age. There was no difference between leaves in their content of the metabolites of ABA, phaseic, and dihydrophaseic acid, expressed per unit weight.

Stomatal responses to changes in atmospheric humidity and water supply



Stomatal responses to changes in atmospheric humidity and water supply: experiments with leaf sections of Zea mays in CO2-free air.

by Raschke K., Kühl U. (1969)

Universität Giessen, Germany

Klaus Raschke, U. Kühl,

in Planta (Berl.) 87, 36–48 –DOI: 10.1007/BF00386962  –

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Leaf sections were exposed to CO2-free air, thus excluding interference by the CO2-sensitive system in the guard cells.

Stomates did not close in response to change from moist to dry air, whether it passed over the leaf or was forced through the intercelluar spaces. In contrast, the stomatal apertures became narrower if the water potential in the liquid supplying the leaf was lowered. Of solutions with the same osmolality, those with the higher viscosity produced the larger responses.

Transient stomatal movements in the opposite direction to the final response were observed upon any sudden change in the water status of the leaf sections, whether caused by varying the moisture content of the air passing around or through the leaf sections, or by varying the water supply.

Increased load on the water supply caused temporary opening movements, while improvements in water supply led to closing movements of varying duration. When dry air was forced through the leaf sections, non-sinusoidal oscillations with large amplitudes were sometimes observed.

It is concluded that the guard cells are tightly coupled to the water-supply system of the leaf and only indirectly to the conditions in the atmosphere by a negative feedback of transpiration on the water potential in the water-conducting system.

No uptake of anions at opening of stomata, guard cells release hydrogen ions



No uptake of anions required by opening stomata of Vicia faba: guard cells release hydrogen ions

by Raschke K., Humble G. D. (1973)

Klaus Raschke, MSU/AEC Plant Research LaboratoryMichigan State UniversityEast LansingUSA

G. D. Humble, Miami Valley LaboratoriesThe Procter & Gamble Co.CincinnatiUSA


in Planta 115: 47-57 – DOI: 10.1007/BF00388604


Epidermal strips from leaves of Vicia faba L. with ruptured epidermal cells and intact guard cells were exposed to solutions of K+ in association with non-absorbable anions. KCl served as control.

Stomata exposed to a range of concentrations of K iminodiacetate, K 4,4-dimethyl-4,7-diazadecane-1,10-disulfonate and K benzene sulfonate opened as widely as on KCl, indicating that K+ can be taken up by guard cells without the necessity of an anion traveling along.

Electroneutrality was maintained by an exchange of K+ for H+. Release of H+ from guard cells was recorded as a drop in the pH of the solution on which the epidermal samples floated.

Formation of acid equivalents by the guard cells was also recorded by automatic titration of the bathing solution at constant pH while CO2 was continuously being removed.

A considerable amount of H+ was released from the epidermis by ion exchange (about 8×10-10eq/mm2). Subtracting this quantity from the total amount of H+ titrated resulted in an estimate of acid production during stomatal opening of 1.2 to 7×10-10 eq/mm2 or 1.5 to 8.5×10-12 eq/stoma. These amounts are equivalent to the known capacity of the guard cells of Vicia faba to absorb K+.

Simultaneous and independent effects of ABA on stomata



Simultaneous and independent effects of abscisic acid on stomata and the photosynthetic apparatus in whole leaves.

by Raschke K., Hedrich R.(1985)

Universität Göttingen, Germany

Klaus Raschke, Rainer Hedrich

in Planta. 1985;163:105–118 – DOI: 10.1007/BF00395904 – 

[PubMed] –


(±)-Abscisic acid (ABA) at 10-5 M was added to the transpiration stream of leaves of 16 species (C3 and C4, monocotyledons and dicotyledons).
Stomatal responses followed one of three patterns:
i) stomata that were wide and insensitive to CO2 initially, closed partially and became sensitive to CO2;
ii) for stomata that were sensitive to CO2 before the application of ABA, the range of highest sensitivity to CO2 shifted from high to low intercellular partial pressures of CO2, for instance in leaves of Zea mays from 170—350 to 70—140 μbar;
iii) when stomata responded strongly to ABA, their conductance was reduced to a small fraction of the initial conductance, and sensitivity to CO2 was lost.
The photosynthetic apparatus was affected by applications of ABA to various degrees, from no response at all (in agreement with several previous reports on the absence of effects of ABA on photosynthesis) through a temporary decrease of its activity to a lasting reduction.
Saturation curves of photosynthesis with respect to the partial pressure of CO2 in the intercellular spaces indicated that application of ABA could produce three phenomena:
i) a reduction of the initial slope of the saturation curve (which indicates a diminished carboxylation efficiency);
ii) a reduction of the level of the CO2-saturated rate of assimilation (which indicates a reduction of the ribulose-1,5-bisphosphate regeneration capacity); and
iii) an increase of the CO2 compensation point.
Photosynthesis of isolated mesophyll cells was not affected by ABA treatments. Responses of the stomatal and photosynthetic apparatus were usually synchronous and often proportional to each other, with the result that the partial pressure of CO2 in the intercellular spaces frequently remained constant in spite of large changes in conductance and assimilation rate.
Guard cells and the photosynthetic apparatus were able to recover from effects of ABA applications while the ABA supply continued. Recovery was usually partial, in the case of the photosynthetic apparatus occasionally complete.
Abscisic acid did not cause stomatal closure or decreases in the rate of photosynthesis when it was applied during a phase of stomatal opening and induction of photosynthesis that followed a transition from darkness to light.

Shuttle of K and Cl between guard cells and subsidiary cells in stomata



Stomatal movement in Zea mays: shuttle of potassium and chloride between guard cells and subsidiary cells.

by Raschke K., Fellows M. (1971)

MSU/AEC Plant Research Laboratory, Michigan State University, East Lansing, USA

Klaus Raschke, M. Fellows,

in Planta 101: 296–316 – doi: 10.1007/BF00398116 –

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When stomates of Zea mays open K and Cl migrate from the subsidiary cells into the guard cells; when the stomates close both elements return to the subsidiary cells.

Subsidiary cells function as reservoirs for K and Cl. Import of K and Cl into the guard cells and loss of both elements from the guard cells become observable 1 or 2 min after light is turned on or off, both when histochemical methods and the electron-probe microanalyzer are used for detection.

Each stomatal complex of maize contains on the average 10±3×10(-13) gram equivalents (eq) of K and 4±1×10(-13) eq of Cl.

Guard cells accumulate K in the light and CO2-free air at an average rate of 10×10(-15) eq K per minute, and Cl at approximately half that rate.

CO2 fixation by isolated epidermises with stomata closed or open.



Carbon dioxide fixation by isolated epidermises with stomata closed or open.

by Raschke K., Dittrich P. (1977)

Institut für Botanik und Mikrobiologie der Technischen Universität München, Arcisstraße 21, D-8000, München 2, Federal Republic of Germany.

Klaus Raschke,

P. Dittrich,


in Planta 134: 69-75. – DOI: 10.1007/BF00390097

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Isolated epidermes of Tulipa gesneriana L. and Commelian communis L. were exposed to 14CO2 in the light and in darkness, when stomata were either closed or open.

The labelling patterns did not differ: the main products of CO2 fixation were malate and aspartate. Small amounts of radioactivity appeared also in acids of the tricarboxylic-acid cycle and their transamination products. Since the capacity of epidermis to assimilate CO2 is known to reside in the guard cells, we can state that guard cells continuously take up CO2 if present, and are thus able to recognize the presence of CO2 in their environment at all times.

Epidermal samples exposed to 14CO2 in the light contained only small amounts of radioactive 3-phosphoglyceric acid (3-PGA) and sugar phosphates, or none at all.

Epidermal samples from Commelina communis did not contain labelled 3-PGA if all adhering mesophyll cells had been removed before exposure to 14CO2. Homogenates of clean epidermal strips of Commelina communis were able to convert exogenous ribulose diphosphate to 3-PGA at a low rate, but could not catalyze the conversion of exogenous ribulose-5-phosphate to ribulose diphosphate.

Guard cells of Commelina communis, and probably also those of Tulipa gesneriana, appear not to possess the reductive pentosephosphate pathway, despite the presence of chloroplasts. In such species, the guard cells will have to rely on import in order to maintain their carbon balance.

Earlier findings of photosynthetic reduction of CO2 by epidermal tissues were probably obtained with samples that were contaminated with mesophyll cells.