Direct and indirect effects of light on stomata

Photo credit : Google

Perilla frutescens – Shiso Perilla Magilla – Beefsteak Plant , Ji Soo , Wild basil

 

Separation and measurement of direct and indirect effects of light on stomata

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

Thomas D. Sharkey, Klaus Raschke,

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. 68:33–40. – DOI: 10.2307/3670169

https://www.jstor.org/stable/4266838?seq=1#page_scan_tab_contents

Abstract

Conductance for water vapor, assimilation of CO2, and intercellular CO2 concentration of leaves of five species were determined at various irradiances and ambient CO2 concentrations. Conductance and assimilation were then plotted as functions of irradiance and intercellular CO2 concentration. The slopes of these curves allowed us to estimate infinitesimal changes in conductance (and assimilation) that occurred when irradiance changed and intercellular CO2 concentration was constant, and when CO2 concentration changed and irradiance was constant.
On leaves of Xanthium strumarium L., Gossypium hirsutum L., Phaseolus vulgaris L., and Perilla frutescens (L.), Britt., the stomatal response to light was determined to be mainly a direct response to light and to a small extent only a response to changes in intercellular CO2 concentration. This was also true for stomata of Zea mays L., except at irradiances < 150 watts per square meter, when stomata responded primarily to the depletion of the intercellular spaces of CO2 which in turn was caused by changes in the assimilation of CO2.
Stomata responded to light even in leaves whose net exchange of CO2 was reduced to zero through application of the inhibitor of photosynthetic electron transport, cyanazine (2-chloro-4[1-cyano-1-methylethylamino]-6-ethylamino-S-triazine). When leaves were inverted and irradiated on the abaxial surface, conductance decreased in the shaded and increased in the illuminated epidermis, indicating that the photoreceptor pigment(s) involved are located in the epidermis (presumably in the guard cells).
In leaves of X. strumarium, the direct effect of light on conductance is primarily a response to blue light. Stomatal responses to CO2 and to light opposed each other. In X. strumarium, stomatal opening in response to light was strongest in CO2 free air and saturated at lower irradiances than in CO2 containing air.
Conversely, stomatal closure in response to CO2 was strongest in darkness and it decreased as irradiance increased. In X. strumarium, P. vulgaris, and P. frutescens, an irradiance of 300 watts per square meter was sufficient to eliminate the stomatal response to CO2 altogether. Application of abscisic acid, or an increase in vapor pressure deficit, or a decrease in leaf temperature reduced the stomatal conductance at light saturation, but when the data were normalized with respect to the conductance at the highest irradiance, the various curves were congruent.
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Voltage dependence of K+ channels in guard cell protoplasts.

 

 

Voltage dependence of K+ channels in guard cell protoplasts.

by Schroeder J. I., Raschke K., Neher E. (1987)

Julian I. Schroeder *, Klaus Raschke t, Erwin Neher *,

*Department of Membrane Biophysics, Max-Planck-Institut fMr biophysikalische Chemie, D-3400 Gottingen, Federal Republic of Germany;

tPflanzenphysiologisches Institut und Botanischer Garten, Universitat Gottingen, D-3400 Gottingen, Federal Republic of Germany

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in Proceedings of the National Academy of Sciences, USA1987;84:4108-4112 –

http://www.esalq.usp.br/lepse/imgs/conteudo_thumb/Voltage-dependence-of-K–channels-in-guard-cell-protoplasts.pdf

ABSTRACT

Stomatal pores in leaves enable plants to regulate the exchange of gases with their environment. Variations of the pore aperture are mediated by controlled changes of potassium salt concentrations in the surrounding guard cells.

The voltage-dependent gating of K+-selective channels in the plasma membrane (plasmalemma) of cell-wall-free guard cells (protoplasts) was studied at the molecular level in order to investigate the regulation of K+ fluxes during stomatal movements.

Inward and outward K+ currents across the plasmalemma of guard cells were identified by using the whole-cell configuration of the patch-clamp technique. Depolarizations of the membrane potential from a holding potential of -60 mV to values more positive than -40 mV produced outward currents that were shown to be carried by KV.

Hyperpolarizations elicited inward K+ currents. Inward and outward currents were selective for K+ over Na’ and could be partially blocked by exposure to extracellular Ba2 . In cell-attached and excised membrane patches, previously identified KV-selective single channels in guard cells were studied.

Averaging of single-channel currents during voltage pulses resulted in activation and deactivation kinetics that were similar to corresponding kinetics of inward and outward currents in whole cells, showing that K+-selective channels were the molecular pathways for the K+ currents recorded across the plasmalemma of single guard cell protoplasts.

Estimates demonstrate that K+ currents through the voltage-gated K+ channels recorded in whole guard cells can account for physiological K+ fluxes reported to occur during stomatal movements in leaves.

The malate requirement for stomatal opening in the light (malate dehydrogenase in guard cells)

 

 

Malate dehydrogenase in guard cells of Pisum sativum

by Scheibe R., Rechmann U., Hedrich R., Raschke K. (1990)

Renate ScheibeUdo ReckmannRainer Hedrich, Klaus Raschke,

Lehrstuhl für Pflanzenphysiologie, Universität Bayreuth, Universitätsstr. 30, 8580 Bayreuth, Federal Republic of Germany
Pflanzenphysiologisches Institut und Botanischer Garten der Universität Göttingen, Untere Karspüle 2, 3400 Göttingen, Federal Republic of Germany

 

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in Plant Physiol. 93: 1358-1364 – DOI: https://doi.org/10.1104/pp.93.4.1358

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1062680/

Abstract

Guard cell protoplasts of Pisum sativum show considerable NADP-dependent malate dehydrogenase (MDH) activity in darkness which can be enhanced severalfold by illumination or treatment with dithiothreitol (DTT). The question arose whether guard cells possess an NADP-MDH different from that present in the chloroplasts of the mesophyll (which is inactive in darkness or in the absence of DTT).

MDH activities were determined in extracts of isolated protoplasts from mesophyll and epidermis, and in mechanically prepared epidermal pieces (with guard cells as the only living cells and no interference from proteases originating from the cell wall digesting enzymes).

Guard cells possessed NAD-dependent MDHs of high activity and incomplete exclusion of NADP as a coenzyme. This NADP-dependent activity of the NAD-MDH(s) could not be stimulated by DTT or, inferentially, by light. The DTT- (and light-) dependent NADP-MDH represented 0.05% of the total protein of the guard cells and had a specific activity of 0.1 unit per milligram protein; both values are in the same range as the corresponding ones of the mesophyll cells.

Agreement was also found in the extent of light activation, in subunit molecular weight, immunological cross-reactions, and in the behavior on an ion exchange column. The activity of the chloroplastic NADP-MDH in guard cells barely suffices to meet the malate requirement for stomatal opening in the light.

It is therefore likely that NAD-MDHs residing in other compartments of the guard cells supplement the activity of the chloroplastic NADP-MDH particularly during stomatal opening in darkness.

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 –

http://www.plantphysiol.org/content/plantphysiol/61/3/361.full.pdf

ABSTRACT

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 – 

Abstract

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  –

Google Scholar

https://link.springer.com/article/10.1007/BF00386962

Summary

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

https://link.springer.com/article/10.1007%2FBF00388604

Summary

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+.