Stomatal aperture and CO2



Temperature dependence of CO2 assimilation and stomatal aperture in leaf sections of Zea mays.

by Raschke K. (1970)

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in Planta 91: 336–363. – doi: 10.1007/Bf00387507 –


CO2 exchange and air flow through the stomata were measured in leaf sections of Zea mays at temperatures between 7 and 52° and under optimal water supply. The results were summarized in polynomials fitted to the data.
In leaf samples brought from 16° and darkness into different experimental temperatures and light, CO2 assimilation has a maximum near 30°. Above 37° (in other experiments above 41°), net CO2 uptake stops abruptly and is replaced by CO2 evolution in light. If a 1-hr treatment with 25° and light is inserted between darkness and the experimental temperatures, the threshold above which the assimilatory system collapses shifts 3 degrees upwards, to 40° (or 44°); the decline of CO2 assimilation with high temperatures is less steep than without pretreatment; and the upper compensation point moves upscale by as much as 5 degrees.
Stomatal conductance for CO2 does not, in general, follow an optimum curve with temperature. Between 15 and 35° it is approximately proportional to net CO2 assimilation, indicating control by CO2; but above 35°, stomatal aperture increases further with temperature (and so does stomatal variability): the stomata escape the control by CO2 and above 40° may be wide open even if CO2 is being evolved. Stomatal conductance for CO2 below 15° may also be larger than would be proportional to CO2 assimilation.
Net CO2 assimilation and stomatal conductance at 25° were reduced if the leaf samples were pretreated with temperatures below approximately 20° and above 30°. Stomata were more sensitive to past temperatures than was CO2 assimilation.

Rubisco activity in stomata



Rubisco activity in guard cells compared with the solute requirement for stomatal opening 

by Reckmann U., Scheibe R., Raschke K. (1990)

Udo Reckmann, Renate Scheibe, Klaus Raschke,

Pflanzenphysiologisches Institut und Botanischer Garten der Universitat Gottingen, Untere Karspule 2, 3400 Gottingen, West Germany (U.R., K.R.),

Botanisches Institut der Universitat Bayreuth, Lehrstuhl Pflanzenphysiologie, Universitatsstrasse 30, 8580 Bayreuth, West Germany (R.S.)


in Plant Physiol. 92: 246–253 – 10.1104/pp.92.1.246 – 

[PMC free article] [PubMed] [Cross Ref] –


We investigated whether the reductive pentose phosphate path in guard cells of Pisum sativum had the capacity to contribute significantly to the production of osmotica during stomatal opening in the light.

Amounts of ribulose 1,5-bisphophate carboxylase/ oxygenase (Rubisco) were determined by the [14C]carboxyarabinitol bisphosphate assay. A guard cell contained about 1.2 and a mesophyll cell about 324 picograms of the enzyme; the ratio was 1:270.

The specific activities of Rubisco in guard cells and in mesophyll cells were equal; there was no indication of a specific inhibitor of Rubisco in guard cells. Rubisco activity was 115 femtomol per guard-cell protoplast and hour. This value was different from zero with a probability of 0.99.

After exposure of guard-cell protoplasts to 14C02 for 2 seconds in the light, about one-half of the radioactivity was in phosphorylated compounds and <10% in malate. Guard cells in epidermal strips produced a different labelling pattern; in the light, <10% of the label was in phosphorylated compounds and about 60% in malate.

The rate of solute accumulation in intact guard cells was estimated to have been 900 femto-osmol per cell and hour. If Rubisco operated at full capacity in guard cells, and hexoses were produced as osmotica, solutes could be supplied at a rate of 19 femto-osmol per cell and hour, which would constitute 2% of the estimated requirement.

The capacity of guard-cell Rubisco to meet the solute requirement for stomatal opening in leaves of Pisum sativum is insignificant.

The ABA contents of isolated stomatal protoplasts



Abscisic-acid contents and concentrations in protoplasts from guard cells and mesophyll cells of Vicia faba L.

by Lahr W., Raschke K. (1988)

Pflanzenphysiologisches Institut und Botanischer Garten, Untere Karspüle 2, D-3400, Göttingen, Federal Republic of Germany.

W. Lahr

Klaus Raschke, Georg-August-Universität Göttingen, Germany


in Planta  173: 528–531 – DOI: 10.1007/BF00958966 –

[Google Scholar] [CrossRef] [PubMed] –


The abscisic-acid (ABA) contents of isolated guard-cell protoplasts and mesophyll-cell protoplasts from Vicia faba were determined by high-pressure liquid chromatography followed by gas chromatography. The amounts of ABA found immediately after preparation of the protoplasts varied from 90 to 570 amol per guard-cell protoplast, and from 75 to 100 amol per mesophyll-cell protoplast. These contents correspond to concentrations between 36 and 230 μmol per liter in guard-cell protoplasts and between 2.7 and 3.3 μmol per liter in mesophyll-cell protoplasts.

During exposure of protoplasts to betaine concentrations of 0.3, 0.5, and 0.8 mol·l(-1) at 0° and 20°C for 30 min, ABA contents as well as the fractions of ABA that leaked into the medium remained constant for both protoplast types.

There was no evidence for net production of ABA in isolated protoplasts subjected to osmotic stress.

Shuttle of potassium and chloride between stomatal guard cells and subsidiary cells



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

by Raschke K., Fellows M. P. (1971)

  • Klaus Raschke,
  • Margaret Pierce Fellows,

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


in Planta 101: 296-316 –


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.

Gain of the feedback loop involving CO2 and stomata



Gain of the feedback loop involving carbon dioxide and stomata.

by Farquhar G. D., Dubbe D. R., Rachke K. (1978)

Graham D. Farquhar, Dean R. Dubbe, Klaus Raschke,

Graham D. Farquhar,

MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824.


in Plant Physiol. 62: 406–412 – PMID: 16660527 PMCID: PMC1092136 – DOI:

CrossRefPubMedGoogle Scholar –


The physiological and physical components of the feedback loop involving intercellular CO(2) concentration (c(i)) and stomata are identified.

The loop gain (G) is a measure of the degree of homeostasis in a negative feedback loop [the expression 1/(1-G) represents the fraction to which feedback reduces a perturbance]. Estimates are given for the effects of G on responses of stomata and c(i) to changes in ambient CO(2) concentration, light intensity, and perturbations in the water relations of a leaf.

At normal ambient CO(2) concentration, the gain of the loop involving stomatal conductance and c(i) was found to be -2.2 in field-grown Zea mays, -3.6 if plants of this species were grown in a growth chamber, and zero in well watered Xanthium strumarium in the vegetative state.

ABA, CO2, stomata and the gains of the feedback loops



Effect of abscisic acid on the gain of the feedback loop involving carbon dioxide and stomata

by Dubbe D. R., Farquhar G. D., Raschke K. (1978)

Dean R. DubbeGraham D. FarquharKlaus Raschke,

MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824.


in Plant Physiol. 62: 413-417 –  DOI:


Gains of the feedback loops involving intercellular CO(2) concentration on one hand, and CO(2) assimilation and stomata on the other (= assimilation loop with gain [G(A)] and conductance loop with gain [G(g)]) were determined in detached leaves of Amaranthus powelli S. Wats., Avena sativa L., Gossypium hirsutum L., Xanthium strumarium L., and Zea mays in the absence and presence of 10(-5)m (+/-) abscisic acid (ABA) in the transpiration stream.

Determinations were made for an ambient CO(2) concentration of 300 microliters per liter. In the absence of ABA, stomata were insensitive to CO(2) (G(g) between 0.00 and -0.02) in A. sativa, G. hirsutum, and X. strumarium, sensitive in A powelli (G(g) = -0.46), and very sensitive in Z. mays (G(g) = -3.6).

Addition of ABA increased the absolute values of the gain of the conductance loop in A. powelli (G(g) = -2.0), G. hirsutum (G(g) = -0.31), and X. strumarium (G(g) = -1.14).

Stomata closed completely in A. sativa. In Z. mays, G(g) decreased after application of ABA to a value of -0.86, but stomatal sensitivity to CO(2) increased for intercellular CO(2) concentrations < 100 microliters per liter. The gain of the assimilation loop increased after application of ABA in all cases, from values between 0.0 (A. powelli) and -0.21 (Z. mays) in the absence of ABA to values between -0.19 (A. powelli) and -0.43 (Z. mays) in the presence of ABA. In none of the species examined did ABA affect the photosynthetic capacity of the leaves.

The application of ABA caused stomatal narrowing which affected transpiration more than the assimilation of CO(2). In the case of A. powelli the transpiration ratio decreased without a concomitant reduction of the assimilation rate.

Osmocytosis and vacuolar fragmentation in stomata



Osmocytosis and vacuolar fragmentation in guard cell protoplasts: their relevance to osmotically-induced volume changes in guard cells.

by Diekmann W., Hedrich R., Raschke K., Robinson D. G. (1993)


Universität Göttingen, Germany


in J. Exp. Bot. 44: 1569–1577 – –


Guard cell protoplasts were prepared from young leaves of pea plants. Under hypertonic conditions they shrink and large numbers of endocytotic (‘osmocytotic’) vacuoles are formed by invagination of the plasma membrane. In thin section these are indistinguishable from other small vacuoles (‘mini-vacuoles’) which are formed by fragmentation of the large central vacuole. However, the two types of vacuole can be individually recognized by labelling the central vacuole with neutral red and by performing the osmotic shrinkage with fluorochromes such as Lucifer Yellow-CH or Cascade Blue present in the extracellular medium. Osmocytotic vacuoles do not fuse with the plasma membrane nor with the mini-vacuoles during a subsequent swelling phase. After several hours, osmocytosed Lucifer Yellow gradually leaks out of the endocytotic vacuoles when protoplasts are returned to hypotonic conditions. This leakage is not prevented by probenecid at concentrations (20–50 mmol m−3) which do not give rise to pathological changes in protoplast ultrastructure. In order to determine the relevance of these observations to the situation in planta, intact guard cells in epidermal strips were first allowed to accumulate neutral red in their vacuoles and then subjected to osmotic shrinkage in the presence of external Lucifer Yellow. Osmocytotic vacuoles were not formed, although the production of mini-vacuoles was frequently observed.