The slow anion channel may be essential for the depolarization of the plasmalemma that is required for salt efflux during stomatal closing

A slow anion channel in guard-cells, activating at large hyperpolarization, may be principal for stomatal closing

Linder B., Raschke K. (1992)

Birgit Linder, Klaus Raschke,

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FEBS Lett. 313: 27–30 – https://doi.org/10.1016/0014-5793(92)81176-M –

https://febs.onlinelibrary.wiley.com/doi/abs/10.1016/0014-5793%2892%2981176-M

Abstract

Slowly activating anion channel currents were discovered at micromolar ‘cytoplasmic’ Ca²⁺ during patch-clamp measurements on guard-cell protoplasts of Vicia faba and Xanthium strumarium. They activated at potentials as low as −200 Mv, with time constants between 5 and 60 s, and no inactivation. The broad voltage dependence exhibited a current maximum near −40 mV. The single-channel open time was in the order of seconds, and the unitary conductance was 33 ps, similar to that of the already described ‘quick’ anion channel of guard cells. Because of its activity at low potentials, the slow anion channel may be essential for the depolarization of the plasmalemma that is required for salt efflux during stomatal closing.

Stomatal closure in groups

Topography of Photosynthetic Activity of Leaves Obtained from Video Images of Chlorophyll Fluorescence

by Daley P. F., Raschke K., Ball J. T., Berry J. A. (1989)

In Plant Physiol. 90: 1233-1238 –

https://www.academia.edu/37479199/Topography_of_Photosynthetic_Activity_of_Leaves_Obtained_from_Video_Images_of_Chlorophyll_Fluorescence

Abstract

Relationship between stomatal conductance and light intensity, derived from experiments using the mesophyll as shade

Relationship between stomatal conductance and light intensity in leaves of Zea mays L., derived from experiments using the mesophyll as shade

by Raschke K., Hanebuth W. F., Farquhar G. D. (1978)

• Klaus Raschke, William F. Hanebuth, Graham D. Farquhar,

MSU-ERDA Plant Research Laboratory, Michigan State University, East Lansing, USA

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In Planta 139: 73-77 – https://doi.org/10.1007/BF00390813 –

https://link.springer.com/article/10.1007/BF00390813

Abstract

Attached leaves of Zea mays were illuminated with monochromatic light, with either the upper or the lower epidermis facing the light source.

The mesophyll absorbed between 99.5 and 99.6% of the red or blue light used. An inversion of the light direction therefore caused a 200- to 250-fold change in the quantum flux into each epidermis. This variation in quantum flux did not affect stomatal conductance.

Stomatal conductance was however correlated with intercellular CO₂ concentration, c_i, and the relationship between stomatal conductance and c_iappeared also to remain the same if changes in c_i were brought about by changes in atmospheric CO₂ concentration instead of light.

A close inspection of the data showed that stomata of the upper (adaxial) epidermis exhibited a small increase in conductance (<0.1 cm s^-1) in response to blue light that was superimposed on the dominating response to c_i.

Abscisic acid content and stomatal sensitivity to CO2 in leaves

Abscisic acid content and stomatal sensitivity to CO2 in leaves of Xanthium strumarium L. after pretreatments in warm and cold growth chambers

by Raschke K., Pierce M., Popiela C. C. (1976)

Klaus Raschke, Margaret Pierce, Chu Chen Popiela,

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In Plant Physiol 57: 115-121 – https://doi.org/10.1104/pp.57.1.115 –

http://www.plantphysiol.org/content/57/1/115

Abstract

The degree of stomatal sensitivity to CO₂ was positively correlated with the content of abscisic acid of leaves of Xanthium strumarium grown in a greenhouse and then transferred for 24 hours or more to a cold (5/10 C, night/day) or a warm growth chamber (20/23 C).

This correlation did not exist in plants kept in the greenhouse continuously (high abscisic acid, no CO₂ sensitivity), nor in plants transferred from the cold to the warm chamber (low abscisic acid, high CO₂ sensitivity).

The abscisic acid content of leaves was correlated with water content only within narrow limits, if at all. At equal water contents, prechilled leaves contained more abscisic acid than leaves of plants pretreated in the warm chamber. There appear to be at least two compartments for abscisic acid in the leaf.

Availability of chloride affects the balance between KCl and potassium malate in guard cells

Availability of chloride affects the balance between potassium chloride and potassium malate in guard cells of Vicia faba L.

by Raschke K., Schnabl H. (1978)

Klaus Raschke, Heide Schnabl,

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In Plant Physiol. 62: 84–87 – DOI: https://doi.org/10.1104/pp.62.1.84 –

http://www.plantphysiol.org/content/62/1/84.short

Abstract

Electron probe microanalysis for K and Cl and enzymic determination of malate were performed on epidermal strips of Vicia faba L. which had been incubated with 0.1 equivalent of K⁺ per liter in the absence or presence of Cl⁻.

In the absence of Cl⁻, iminodiacetate, a presumed impermeant zwitterion, served as anion. With no Cl⁻ in the medium, 91% of the K⁺ imported into the guard cells during stomatal opening was neutralized by malate production; import of Cl⁻ (presumably from the rest of the epidermal tissue) contributed 6%.

In the presence of Cl⁻, 50% of the necessary negative charges were provided by malate synthesis, 45% by Cl⁻ import.

Stomatal opening was not obviously affected by the chloride concentration in the incubation medium, but malate production declined roughly linearly with the logarithm of [Cl⁻] between 10⁻⁵ and 10⁻¹ equivalent per liter.

Rapid epidermal and stomatal responses to changes in water supply

Leaf hydraulic system: rapid epidermal and stomatal responses to changes in water supply

by Raschke K. (1970)

Klaus Raschke,

In Science 167: 189–191 – DOI: 10.1126/science.167.3915.189 –

http://science.sciencemag.org/content/167/3915/189

Abstract

The epidermis of the leaf of Zea mays transmits changes it water potential in the water supply of the leaf to the stomata within 0.1 second.

Reduction in water supply can cause the subsidiary cells surrounding the stomata to collapse within 1.5 minutes, and the epidermis to shrink to one-third of its original thickness within 20 minutes.

Effect of light quality on stomatal opening

Effect of light quality on stomatal opening in leaves of Xanthium strumarium L.

by Sharkey T. D., Raschke K. (1981)

Thomas D. Sharkey, Klaus Raschke,

1 MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824² 

2 Present address: Research School of Biological Sciences, Australian National University, P.O. Box 475, Canberra City, ACT 2601, Australia.

³ Present address: Pflanzenphysiologisches Institut der Universität Göttingen, Untere Karspüle 2, 3400 Göttingen, Federal Republic of Germany.

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In Plant Physiol 68: 1170–1174 – DOI: https://doi.org/10.1104/pp.68.5.1170 –

http://www.plantphysiol.org/content/68/5/1170

Abstract

Flux response curves were determined at 16 wavelengths of light for the conductance for water vapor of the lower epidermis of detached leaves of Xanthium strumarium L.

An action spectrum of stomatal opening resulted in which blue light (wavelengths between 430 and 460 nanometers) was nearly ten times more effective than red light (wavelengths between 630 and 680 nanometers) in producing a conductance of 15 centimoles per square meter per second. Stomata responded only slightly to green light.

An action spectrum of stomatal responses to red light corresponded to that of CO₂ assimilation; the inhibitors of photosynthetic electron transport, cyanazine (2-chloro-4[1-cyano-1-methylethylamino]-6-ethylamino-s-triazine) and 3-(3,4-dichlorophenyl)-1,1-dimethylurea, eliminated the response to red light. This indicates that light absorption by chlorophyll is the cause of stomatal sensitivity to red light.

Determination of flux response curves on leaves in the normal position (upper epidermis facing the light) or in the inverted position (lower epidermis facing the light) led to the conclusion that the photoreceptors for blue as well as for red light are located on or near the surfaces of the leaves; presumably they are in the guard cells themselves.

Potassium chloride as stomatal osmoticum

Potassium Chloride as Stomatal Osmoticum in Allium cepa L., a Species Devoid of Starch in Guard Cells

by Schnabl H., Raschke K. (1980)

• Heide Schnabl,, University of Bonn (Bonn, Germany)
• Klaus Raschke, Georg-August-Universität Göttingen, Germany
  
  

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In Plant Physiol. 65(1): 88–93 – PMID: 16661151 PMCID: PMC440273 – 

https://www.ncbi.nlm.nih.gov/pubmed/16661151

Abstract

K(+) and Cl(-) contents of guard cells and of ordinary epidermal cells were determined in epidermal samples of Allium cepa L. by electron probe microanalysis; malate contents of the same samples were determined by enzymic oxidation.

KCl was, in general, the major osmoticum in guard cells, irrespective of whether stomata had opened on leaves or in epidermal strips floating on solutions. The solute requirement varied between 50 and 110 femtomoles KCl per micrometer increase in aperture per pair of guard cells. Stomata did not open on solutions of K iminodiacetate, presumably because its anion could not be taken up.

Stomata opened if KCl or KBr was provided. Taken together, the results indicate that the absence of starch from guard cells deprived them of the ability to produce malate in amounts of osmotic consequence and that the presence of absorbable Cl(-) (or Br(-)) was necessary for stomatal opening.

Previous nutrient supply of the plants determined whether the charges of K(+) in guard cells were completely balanced by Cl(-) or only partially. Addition of K(2)SO(4) to the nutrient solution reduced the participation of Cl(-) in stomatal ion transfer, even if epidermal strips of these plants were later exposed to KCl solution.

The anion supplying the charge complement in these cases is not known. Although malate appeared not to participate in stomatal ion transfer in onion, epidermal samples of this species did contain malate. Malate accumulated in the epidermis of leaves put into the light but disappeared from illuminated epidermal strips floating on solutions. In whole leaves, epidermal malate content was positively correlated with stomatal opening; in epidermal strips floating on solutions, the correlation was negative or absent.

Rates of sugar uptake by stomatal guard cell protoplasts

Rates of sugar uptake by guard cell protoplasts of Pisum sativum L. – Related to the solute requirement for stomatal opening

by Ritte G., Rosenfeld J., Rohrig K., Raschke K. (1999)

Gerhard Ritte, Johanna Rosenfeld, Kerstin Rohrig, Klaus Raschke,

Albrecht-von-Haller-Institut für Pflanzenwissenschaften, Universität Göttingen, Untere Karspüle 2, 37073 Göttingen, Germany

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In Plant Physiol 121: 647–656 – doi: 10.1104/pp.121.2.647 – 

http://www.plantphysiol.org/content/121/2/647

Abstract

We wished to determine whether the capacity of the sugar uptake mechanisms of guard cells of the Argenteum mutant of pea (Pisum sativum L.) sufficed to support a concurrent stomatal opening movement.

Sugar uptake by guard cell protoplasts was determined by silicone-oil-filtering centrifugation. The protoplasts took up [¹⁴C]glucose, [¹⁴C]fructose, and [¹⁴C]sucrose (Suc), apparently in symport with protons. Mannose, galactose, and fructose competed with Glc for transport by a presumed hexose carrier. The uptake of Glc saturated with aK_m of 0.12 mm and aV_max of 19 fmol cell⁻¹h⁻¹. At external concentrations <1 mm, the uptake of Suc was slower than that of Glc. It exhibited a saturating component with a K_m varying between 0.25 and 0.8 mm and a V_max between 1 and 10 fmol cell⁻¹ h⁻¹, and at external concentrations >1 mm, a non-saturating component.

At apoplastic sugar concentrations below 4 mm, sugar import was estimated to be mainly in the form of hexoses and too slow to support a simultaneous stomatal opening movement. If, however, during times of high photosynthesis and transpiration, the apoplastic Suc concentration rose and entered the range of non-saturating import, absorbed Suc could replace potassium malate as the osmoticum for the maintenance of stomatal opening.

Metabolites released by illuminated stomatal chloroplasts originated predominantly from starch breakdown

Vicia faba – Manual of the Alien Plants of Belgium

Metabolite export of isolated guard cell chloroplasts of Vicia faba

by Ritte G., Raschke K. (2003)

Gerhard Ritte, Klaus Raschke,

University of Göttingen, Germany

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In New Phytologist 159: 195–202 – https://doi.org/10.1046/j.1469-8137.2003.00789.x –

https://nph.onlinelibrary.wiley.com/doi/full/10.1046/j.1469-8137.2003.00789.x

Abstract

• •Stomatal opening is caused by guard cell swelling due to an accumulation of osmotica. We investigated the release of carbon from guard cell chloroplasts as a source for the production of organic osmotica.
• •Photosynthetically active chloroplasts were isolated from guard cell protoplasts of Vicia faba. Export of metabolites into the surrounding medium was analyzed by silicone oil filtering centrifugation and spectrophotometrically by coupled metabolite assays. Effects of external oxaloacetate and 3‐phosphoglycerate on photosynthetic electron transport were examined by recording chlorophyll fluorescence.
• •In the light, guard cell chloroplasts exported triose phosphates, glucose, maltose and hexose phosphates. The presence of phosphate in the medium was essential for the release of phosphorylated compounds and also strongly enhanced the export of glucose and maltose. Total efflux of carbon from illuminated guard cell chloroplasts was on average 486 µatom C (mg Chl)⁻¹ h⁻¹, which was significant with respect to the carbon requirement for stomatal opening.
• •Metabolites released by illuminated guard cell chloroplasts originated predominantly from starch breakdown. Photosynthetic electron transport provided redox power for the reduction of oxaloacetate and 3‐phosphoglycerate.