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  • 1
    Digitale Medien
    Digitale Medien
    Variations in stomatal density and index: implications for palaeoclimatic reconstructions (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 19 (1996), S. 0 
    Details
    ISSN: 1365-3040
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: The variation in stomatal characters in leaves from one Alnus glutinosa (L.) Gaertn. tree is analysed. Measurements were taken from over 70 sites on the abaxial surfaces of representative ‘sun’ and ‘shade’ leaves having the same insertion point. The mean values of stomatal density and index in the shade leaf were significantly lower (71 and 93%, respectively) than those for the sun leaf. Within leaves, up to 2.5-fold differences in stomatal density values were observed. Contour maps derived from the data reveal non-random trends over the leaf surface. Correlations between stomatal density, epidermal cell density and stomatal index indicate that the variation in stomatal density within leaves arose primarily from local differences in stomatal differentiation, rather than from local differences in leaf expansion. This research demonstrates that a high level of variation in stomatal characters occurs both within and between leaves. We conclude that a well-defined sampling strategy should be used when estimating stomatal characters for (tree) leaves. Furthermore, the leaf's insertion point and situation within the tree crown should be taken into account. We discuss the implications of these findings for palaeoclimatic interpretations and emphasize the need for great caution when drawing conclusions based solely on stomatal characters.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-3040.1996.tb00405.x
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  • 2
    Digitale Medien
    Digitale Medien
    Variation in stomatal characteristics over the lower surface of Commelina communis leaves (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 12 (1989), S. 0 
    Details
    ISSN: 1365-3040
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Abstract. The silicone rubber impression technique was used to measure stomatal apertures in 9 mm2 sampling areas covering the entire lower surface of leaves of Commelina communis L. The data were analysed using a computer program which produced ‘iso-aperture' contours illustrating local differences in mean stomatal aperture. Little consistency was seen in the iso-aperture patterns among sampling times, although the stomata were always relatively closed at the leaf tip and base. When stomata in the middle of the lamina were open, those near to the leaf margin tended to be relatively closed. In places, gradients of mean stomatal aperture were as high as 1 μm mm−1. Measurements along a transect across the lower epidermis revealed no correlation of stomatal aperture with the presence of major veins in the mesophyll tissue. Variation in guard-cell size and stomatal frequency on the lower leaf surface was also analysed. The guard cells were smallest and the stomata more frequent near to the leaf margins. The significance of the results is discussed in relation to measurements of leaf conductance and models of stomatal function.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-3040.1989.tb01234.x
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  • 3
    Digitale Medien
    Digitale Medien
    Towards a quantitative definition of plant hormone sensitivity (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 10 (1987), S. 0 
    Details
    ISSN: 1365-3040
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Abstract A definition of plant hormone sensitivity is proposed which is based on the initial rates of responses at different hormone concentrations. By analogy with enzyme kinetics, it is concluded that simple concentration-response curves can be described by a function containing three ‘sensitivity parameters’. Objective methods for determining the values of these parameters and for comparing curves are described. These methods are used to describe the responses of Commelina communis L. stomata to abscisic acid. If certain assumptions are valid, the sensitivity parameters can be assigned physicochemical meanings. To validate the assumptions, certain experimental criteria must be fulfilled and these are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-3040.1987.tb02073.x
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  • 4
    Digitale Medien
    Digitale Medien
    The effect of pH on stomatal sensitivity to abscisic acid (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 11 (1988), S. 0 
    Details
    ISSN: 1365-3040
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Abstract. The sensitivity of stomata of Commelina communis L. to abscisic acid (ABA) was evaluated by analysing the initial rates of response to the compound at different hormone concentrations. This was carried out at pH 6.8 and pH 5.5. The data were modelled and statistically analyzed by means of a computer program employing non-linear regression techniques and step-down analysis of variance. The response kinetics as quantified in terms of three sensitivity parameters were found to differ significantly between the two pH values. This finding is discussed in relation to previous research on purified ABA-binding proteins.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1365-3040.ep11604886
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  • 5
    Digitale Medien
    Digitale Medien
    Abscisic acid and guard cells of Commelina communis L. (1978)
    [s.l.] : Nature Publishing Group
    Nature 271 (1978), S. 652-653 
    Details
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] Figure 1 shows that during 1 h when 2-14C-ABA was supplied through the transpiration stream there was a substantial increase in the radioactivity present in the lower epidermis. Stomatal closure was complete 9 min after application of ABA. These data enable us to calculate an upper limit for the ...
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1038/271652a0
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  • 6
    Digitale Medien
    Digitale Medien
    Sensitivity of Commelina stomata to abscisic acid (1979)
    Springer
    Planta 146 (1979), S. 623-628 
    Details
    ISSN: 1432-2048
    Schlagwort(e): Abscisic acid ; Commelina ; Microautoradiography ; Stomatal sensitivity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Stomata of Commelina leaves pre-opened by incubation in moist air were found to close within 30 min when supplied with abscisic acid (ABA) via the transpiration stream. Radioactive ABA had similar effects, but allowed the distribution of the compound within the leaf to be measured and correlated with stomatal movements to give estimates of the sensitivity of Commelina stomata. On a whole-leaf basis, less than 163 fmol ABA per mm2 leaf area were present at the time of complete stomatal closure. This was close to other published estimates. By taking epidermal 14C measurements, however, it was possible to increase the accuracy of the estimate on the assumption that only ABA present in the epidermis was physiologically active. Thus, less than 235 amol ABA for stomatal complex were present at complete closure, and statistically significant narrowing of the stomatal aperture had occurred when between 12.6 and 45.4 amol per complex were present. The distribution of ABA within the epidermal tissue after transpiration-stream application was studied using microautoradiography, and the compound appeared to have accumulated within the stomatal complex.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00388842
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  • 7
    Digitale Medien
    Digitale Medien
    Uptake and distribution of abscisic acid in Commelina leaf epidermis (1979)
    Springer
    Planta 144 (1979), S. 167-172 
    Details
    ISSN: 1432-2048
    Schlagwort(e): Abscisic acid ; Commelina ; Epidermal strip ; Stomatal closure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Closure of stomata by abscisic acid (ABA) was studied by floating leaf epidermal strips of Commelina communis L. in PIPES buffer (pH 6.8) containing a range of KCl concentrations. Control apertures were greatest at high concentrations of the salt, and the effects of ABA, in terms of closure, were most pronounced below 100 mol m-3 KCl. Stomata opened on strips floated on buffer plus 50 mol m-3 KCl and closed within 10 min when transferred to the same medium plus 0.1 mol m-3 ABA. [2-14C]ABA was used to study uptake and distribution of the hormone by the epidermal strips. It was calculated that no more than 6 fmol ABA were present per stomatal complex at the time of closure, although uptake continued thereafter. Microautoradiography indicated that radioactivity from [2-14C]ABA accumulated in the stomatal complex at or near the guard cells within 20 min. TLC was used to examine the state of the label after 1 h incubation. Efflux of label from preincubated tissue appeared to occur in three phases (t1/2=7.2 s, 4.0 min, 35.2 min). Efflux was correlated with stomatal re-opening. The results confirm that ABA can accumulate in the epidermis of C. communis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00387266
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