Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “STOMATITIS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 235 records · Page 13Linked to original sources
PubMed1995

Actin Filaments in Mature Guard Cells Are Radially Distributed and Involved in Stomatal Movement.

Stomatal movements, which regulate gas exchange in plants, involve pronounced changes in the shape and volume of the guard cell. To test whether the changes are regulated by actin filaments, we visualized microfilaments in mature guard cells and examined the effects of actin antagonists on stomatal movements. Immunolocalization on fixed cells and microinjection of fluorescein isothiocyanate-phalloidin into living guard cells of Commelina communis L. showed that cortical microfilaments were radially distributed, fanning out from the stomatal pore site, resembling the known pattern of microtubules. Treatment of epidermal peels with phalloidin prior to stabilizing microfilaments with m-maleimidobenzoyl N-hydroxysuccimimide caused dense packing of radial microfilaments and an accumulation of actin around many organelles. Both stomatal closing induced by abscisic acid and opening under light were inhibited. Treatment of guard cells with cytochalasin D abolished the radial pattern of microfilaments; generated sparse, poorly oriented arrays; and caused partial opening of dark-closed stomata. These results suggest that microfilaments participate in stomatal aperture regulation.

Journal Article↗
PubMed1997

Actin Filaments Modulate Both Stomatal Opening and Inward K+-Channel Activities in Guard Cells of Vicia faba L.

Actin antagonists have previously been shown to alter responses of Commelina communis stomata to physiological stimuli, implicating actin filaments in the control of guard cell volume changes (M. Kim, P.K. Hepler, S.-O. Eun, K.S. Ha, Y. Lee [1995] Plant Physiol 109: 1077-1084). Since K+ channels in the guard cell play an important role in stomatal movements, we examined the possible regulation of K+-channel activities by the state of actin polymerization. Agents affecting actin polymerization altered light-induced stomatal opening and inward K+-channel activities measured by patch clamping in Vicia faba. Cytochalasin D, which induces depolymerization of actin filaments, promoted light-induced stomatal opening and potentiated the inward K+ current in guard cell protoplasts. Phalloidin, a stabilizer of filamentous actin, inhibited both light-induced stomatal opening and inward K+ current. Inward K+-channel activities in outside-out membrane patches showed responses to these agents that support results at the whole-cell current level, suggesting that cytochalasin D facilitates and phalloidin inhibits K+ influx in intact guard cells, thus resulting in enhancement and inhibition of stomatal opening, respectively. To our knowledge, this is the first report that provides evidence that actin filaments may regulate an important physiological process by modulating the activities of ion channels in plant cells.

Journal Article↗
PubMed2000

The ultraviolet action spectrum for stomatal opening in broad bean.

The ultraviolet action spectrum for stomatal opening was measured using epidermal peels from leaves of broad bean (Vicia faba). The spectrum was calculated from hyperbolic fluence response curves using 11 wavelengths ranging from 275 to 459 nm. The action spectrum exhibits a major peak at approximately 280 nm and a minor peak at approximately 360 nm. The response at 280 nm is about three times greater than the response at 459 nm. Under the conditions utilized (i.e. the absence of saturating red light), stomatal opening saturated at extremely low fluence rates: <0.2 micromol m(-2) s(-1) at 280 nm, and approximately 1.0 micromol m(-2) s(-1) at 459 nm. The threshold for blue-light-induced stomatal opening was approximately 0.02 micromol m(-2) s(-1). In light-mixing experiments, the addition of 280 nm light to saturating 650 nm (red) light caused additional stomatal opening, which is indicative of separate photoreceptors. In contrast, adding 280 nm of light to saturating 459 nm (blue) light did not increase stomatal opening, suggesting that they both excite the same receptor. The results with white light were similar to those with blue light. We infer that ultraviolet light acts via the blue light photoreceptor rather than through photosynthesis. The additional absorbance peak at 360 nm suggests that the chromophore is either a flavin or a cis-carotenoid, both of which exhibit peaks in this region. It is proposed that the chromophore can be excited either directly by blue light or by energy transferred from the protein portion of the protein-pigment complex after it absorbs 280 nm light.

Fabaceae↗
PubMed1970

Stomatal dimensions and resistance to diffusion.

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.

Journal Article↗
PubMed1972

Potassium Deficiency-induced Changes in Stomatal Behavior, Leaf Water Potentials, and Root System Permeability in Beta vulgaris L.

Studies of the water relations of potassium deficient sugarbeet plants (Beta vulgaris L.) revealed two factors for stomatal closure. One component of stomatal closure was reversible by floating leaf discs on distilled water to relieve the water deficit in the leaves; the other component was reversible in the light by floating the leaf discs on KCl solution for 1 hour or more. Potassium-activated stomatal opening in the light was observed when the guard cells were surrounded by their normal environment of epidermal and mesophyll cells, just as observed by previous workers for epidermal strips. Leaf water potentials, like stomatal apertures, appear to be strongly related to leaf potassium concentration. Potassium-deficient plants have a greatly decreased root permeability to water, and the implications of this effect on stomatal aperture and leaf water potential are discussed. In contrast, petiole permeability to water is unaffected by potassium treatment.

Journal Article↗
PubMed1972

Saturation Kinetics of the Velocity of Stomatal Closing in Response to CO(2).

Stomatal closing movements in response to changes from CO(2)-free to CO(2)-containing air were recorded in leaf sections of Zea mays using air flow porometers. The response to CO(2) was fast; the shortest lag between the application of 300 microliters CO(2) per liter of air and the beginning of a stomatal response was 3 seconds. The velocity of stomatal closing increased with CO(2) concentration and approached its maximal value between 10(3) and 10(4) microliters CO(2) per liter of air. The CO(2) concentration at which the closing velocity reached half its maximal value was approximately 200 microliters CO(2) per liter of air, both in the light and in darkness. This indicates that the mechanism of stomatal responses to CO(2) is the same in both light regimes and that the range of stomatal sensitivity to changes in CO(2) concentration coincides with the range of CO(2) concentrations known to occur in the intercellular spaces of illuminated leaves.

Journal Article↗
PubMed1972

Stomatal conductance of differentially salinized plants.

Stomatal resistance was measured daily with a stomatal diffusion porometer during a 4-week period in leaves of bean (Phaseolus vulgaris L., var. Bush Blue Lake) and barley (Hordeum vulgare L., var. Liberty) plants having roots equally split between two differentially salinized nutrient solutions. The stomatal conductance (reciprocal of stomatal resistance) of plants with half their roots in saline solutions was intermediate between the stomatal conductances of plants grown in nonsaline solutions and those grown in saline solutions.

Journal Article↗
PubMed1973

Organic Acid Changes in the Epidermis of Vicia faba and Their Implication in Stomatal Movement.

Considerable evidence indicates that the increase in guard cell turgor resulting in stomatal opening is brought about by active K(+) uptake into guard cells. Only a small increase in inorganic anions appears to accompany the increase in K(+). A plausible explanation is that organic acids are produced within guard cells and act as counterions, whereas the H(+) produced are exchanged for K(+).This hypothesis was tested by using different levels of ambient CO(2) in light to control stomatal aperture and at the same time measure changes in organic acid production in the epidermis of Vicia faba. Epidermal strips were used, quickly frozen in liquid nitrogen, and later extracted.A positive correlation was found between stomatal resistance (r(s), indirect measure of stomatal aperture) and CO(2) level. With decreases in r(s), total titratable acidity increased. The organic acids, glyceric, malic, and citric, in the epidermis, as measured by gas chromatography of trimethylsilyl derivatives, increased. Changes in glucose or sucrose were not found. These analyses provided evidence that organic acid production in the epidermis is associated with stomatal opening.

Journal Article↗
PubMed1975

Relationships between Leaf Water Status, Abscisic Acid Levels, and Stomatal Resistance in Maize and Sorghum.

A new method for abscisic acid extraction and purification was developed to handle large numbers of small (about 125 milligrams fresh weight) samples of leaf discs. This method enabled short term changes in abscisic acid to be followed in single leaves.Water potentials, stomatal diffusion resistance, and abscisic acid levels were measured in the leaves of maize (Zea mays L. var. Wisconsin 575) and sorghum (Sorghum bicolor, hybrid NK 145) plants subjected to a drought-recovery cycle under controlled environmental conditions. The levels of abscisic acid began to rise, and the stomata closed, over a narrow range of water potential (-8 to -10 bars) in both species. Abscisic acid levels continued to rise after the stomata closed. The maximum amount of abscisic acid extracted from maize leaves was about twice that from sorghum, but this represented a similar proportional increase over the control level.In excised leaves little or no change in abscisic acid levels was found within 60 to 120 minutes after stress was applied (phase I). Subsequently abscisic acid levels rose rapidly to about 20 times the prestress level (phase II). Stomatal closure always preceded the phase II increase in abscisic acid.The aftereffects of stress differed in the two species. In sorghum control levels of both abscisic acid and stomatal resistance were regained within 24 hours of rewatering. In maize abscisic acid levels also fell rapidly, but regained control levels only after 48 hours. The resumption of normal stomatal functioning occurred after a further 24 hours.Impaired stomatal functioning after stress does not appear to be associated with high residual levels of abscisic acid in the leaf.

Journal Article↗
PubMed1976

Stomatal response of engelmann spruce to humidity, light, and water stress.

Stomatal response of Engelmann spruce (Picea engelmannii Engelm.) to environmental conditions was studied in the natural subalpine environment and under controlled laboratory conditions. Stomata of naturally occurring trees responded to the difference in absolute humidity from leaf to air. When foliage was exposed to full sunlight, stomatal conductance decreased as the absolute humidity difference increased. In the shade, where photosynthetically active radiation was 10% of that in full sunlight, stomatal closure at large absolute humidity differences was much more complete. No effect of soil or air temperatures on stomatal aperture was observed in the field, nor were differences among three contrasting sites detected. Under growth chamber conditions, stomata responded to photosynthetically active radiation, but conductances were influenced by leaf-to-air differences in absolute humidity. Leaf water potentials below - 15 bars resulted in lower conductances over a range of humidity and light conditions. Because net photosynthesis under shaded conditions in the natural environment must be very low, stomatal closure could result in considerable savings in water while having a minimum effect on net photosynthesis.

Journal Article↗
PubMed1979

Environmental Influences on Open Stomates of a Crassulacean Acid Metabolism Plant, Agave deserti.

The major short term stomatal response of Agave deserti was to temperature; increases in leaf temperature led to decreases in water vapor conductance for stomatal opening during the daytime (C(3) mode) as well as at night (Crassulacean acid metabolism or CAM mode). Hourly changes in the water vapor concentration drop from leaf to air had no significant stomatal effect in either mode. Stomatal responses to external CO(2) levels up to 800 microliters per liter were not significant after 15 minutes and only moderate after a few hours, suggesting that CO(2) effects on open stomates of this succulent were indirect in both CAM and C(3) modes.

Journal Article↗
PubMed1982

Stomatal behavior and water relations of waterlogged tomato plants.

The effects of waterlogging the soil on leaf water potential, leaf epidermal conductance, transpiration, root conductance to water flow, and petiole epinasty have been examined in the tomato (Lycopersicon esculentum Mill.). Stomatal conductance and transpiration are reduced by 30% to 40% after approximately 24 hours of soil flooding. This is not due to a transient water deficit, as leaf water potential is unchanged, even though root conductance is decreased by the stress. The stomatal response apparently prevents any reduction in leaf water potential. Experiments with varied time of flooding, root excision, and stem girdling provide indirect evidence for an influence of roots in maintaining stomatal opening potential. This root-effect cannot be entirely accounted for by alterations in source-sink relationships. Although 1-aminocyclopropane-1-carboxylic acid, the immediate precursor of ethylene, is transported from the roots to the shoots of waterlogged tomato plants, it has no direct effect on stomatal conductance. Ethylene-induced petiole epinasty develops coincident with partial stomatal closure in waterlogged plants. Leaf epinasty may have beneficial effects on plant water balance by reducing light interception.

Journal Article↗
PubMed1983

Stomatal sensitivity to carbon dioxide and humidity: a comparison of two c(3) and two c(4) grass species.

The sensitivity of stomatal conductance to changes of CO(2) concentration and leaf-air vapor pressure difference (VPD) was compared between two C(3) and two C(4) grass species. There was no evidence that stomata of the C(4) species were more sensitive to CO(2) than stomata of the C(3) species. The sensitivity of stomatal conductance to CO(2) change was linearly proportional to the magnitude of stomatal conductance, as determined by the VPD, the same slope fitting the data for all four species. Similarly, the sensitivity of stomatal conductance to VPD was linearly proportional to the magnitude of stomatal conductance. At small VPD, the ratio of intercellular to ambient CO(2) concentration, C(i)/C(a), was similar in all species (0.8-0.9) but declined with increasing VPD, so that, at large VPD, C(i)/C(a) was 0.7 and 0.5 (approximately) in C(3) and C(4) species, respectively. Transpiration efficiency (net CO(2) assimilation rate/transpiration rate) was larger in the C(4) species than in the C(3) species at current atmospheric CO(2) concentrations, but the relative increase due to high CO(2) was larger in the C(3) than in the C(4) species.

Journal Article↗
PubMed1985

Water Stress Reduces Ozone Injury via a Stomatal Mechanism.

Various studies have shown that water-stressed plants are more tolerant of ozone exposures than are unstressed plants. Two probable explanations for this tolerance are (a) stomatal closure which reduces ozone uptake and (b) biochemical or anatomical changes within the leaves. Phaseolus vulgaris cv Pinto bean plants were established and transferred to membrane systems which controlled the osmotic potential around the roots at -35 or -80 kilopascals for 5 days prior to ozone treatment (0 or 1.0 microliters per liter for 2 hours). Both water-stressed and unstressed plants were sprayed with various concentrations of abscisic acid to close the stomata or with fusicoccin to induce stomata opening. The abaxial stomatal resistances of primary and trifoliate leaves were measured just prior to ozone exposure. Plant response to ozone was determined by stress ethylene production and chlorophyll loss. Both water stress and abscisic acid induced stomatal closure and reduced ozone injury. In water-stressed plants, fusicoccin induced stomatal opening and those plants were as sensitive to ozone as were the non-water-stressed plants. These data suggest that water stress protects plants from ozone injury mainly through its influence on stomatal aperture rather than through biochemical or anatomical changes.

Journal Article↗
PubMed1985

Effects of Nitrate Application on Amaranthus powellii Wats. : III. Optimal Allocation of Leaf Nitrogen for Photosynthesis and Stomatal Conductance.

Optimal allocation of leaf nitrogen maximizes daily CO(2) assimilation for a given leaf nitrogen concentration. According to the hypothesis of optimization, this condition occurs when the partial derivative of assimilation rate with respect to leaf nitrogen concentration is constant. This hypothesis predicts a linear increase of assimilation rate with leaf nitrogen concentration under constant conditions. Plants of Amaranthus powellii Wats. were grown at 1, 5, 10, or 45 millimolar nitrate to obtain leaves with different nitrogen concentrations. Assimilation rate at 340 microbar CO(2)/bar, stomatal conductance, CO(2)- and light-saturated net photosynthetic rate, the initial slope of the CO(2) response of photosynthesis, ribulose-1,5'-bisphosphate carboxylase activity, and phosphoenolpyruvate carboxylase activity were linearly related to estimated or actual leaf nitrogen concentration. The data are consistent with the optimal use of leaf nitrogen. This hypothesis and the hypothesis of optimal stomatal conductance were combined to determine the relationship between conductance and leaf nitrogen concentration. The slope of conductance versus leaf nitrogen concentration was not significantly different than the slope predicted by the combination of the two hypotheses. Stomatal conductance was linearly related to leaf nitrogen in the field and the slope decreased with lower xylem pressure potentials in a manner consistent with the hypotheses. Finally, apparent maximum stomatal aperture of isolated abaxial epidermal strips was linearly related to leaf nitrogen suggesting stomatal conductance and assimilation rate are controlled in parallel by leaf nitrogen concentration or some factor correlated with leaf nitrogen.

Journal Article↗
PubMed1989

Repeated measurements of aperture for individual stomates.

Measurements of stomatal aperture in epidermal peels are used in a variety of physiological studies, but variability between stomates often hinders experimentation. We mount epidermal peels of Vicia faba over a microscopic grid that enables us to map the positions of individual stomates and thus measure the same individual stomates repeatedly, using a simple digitizing system. Repeated measurements of the same population of 15 stomates show much lower variability than measurements of different populations either on the same peel or on different peels.

Journal Article↗
PubMed1989

Circadian Stomatal Rhythms in Epidermal Peels from Vicia faba.

Circadian rhythms in stomatal aperture and in stomatal conductance have been observed previously. Here we investigate circadian rhythms in apertures that persist in functionally isolated guard cells in epidermal peels of Vicia faba, and we compare these rhythms with rhythms in stomatal conductance in attached leaves. Functionally isolated guard cells kept in constant light display a rhythmic change in aperture superimposed on a continuous opening trend. The rhythm free-runs with a period of about 22 hours and is temperature compensated between 20 and 30 degrees C. Functionally isolated guard cell pairs are therefore capable of sustaining a true circadian rhythm without interaction with mesophyll cells. Stomatal conductance in whole leaves displays a more robust rhythm, also temperature-compensated, and with a period similar to that observed for the rhythm in stomatal aperture in epidermal peels. When analyzed individually, some stomata in epidermal peels showed a robust rhythm for several days while others showed little rhythmicity or damped out rapidly. Rhythmic periods may vary between individual stomata, and this may lead to desynchronization within the population.

Journal Article↗
PubMed1990

Effect of Potassium Levels on the Stomatal Behavior of the Hemi-Parasite Striga hermonthica.

The hemi-parasite Striga hermonthica, exhibits an anomalous pattern of stomatal response, stomata remaining open in darkness and when subjected to water stress. This suggests irregularity in stomatal response due to malfunction of the stomatal mechanism. To test this suggestion guard cells were isolated from the effects of surrounding cells, by incubating epidermal strips at low pH. These stomata responded rapidly to low CO(2) concentrations, darkness, and ABA. Thus, a paradox exists between stomatal behavior observed in whole leaves and that in isolated guard cells. However, when incubated in the presence of high potassium concentrations (>200 millimolar KCl) stomatal responses in epidermal strips resembled those found in whole leaves, with enhanced opening and reduced closing responses. It is suggested that the anomalous behavior of stomata in Striga and other leafy hemiparasites can be explained by the modulatory effects of high potassium concentrations which accumulate in the leaves as a consequence of high transpiration rates and the lack of a retranslocation system.

Journal Article↗