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Effects of Calcium and Abscisic Acid on Volume Changes of Guard Cell Protoplasts of Commelina 总被引:1,自引:0,他引:1
Calcium ions contracted guard cell protoplasts (GCP) of Commelinacommunis L., being particularly effective within the concentrationrange of 0 to 0.2 mol m3. Abscisic acid (ABA) in thepresence of EGTA, which chelates free Ca2+ in the medium, contractedGCP to a similar extent to Ca2+ alone or Ca2+ and ABA together.Similarly, ABA in the absence of free Ca2+ (i.e. an ABA/EGTAtreatment) inhibited K+-induced swelling of contracted GCP,as did Ca2+ alone or ABA and Ca2+ together. Lanthanum, a Ca2+channel blocker, prevented the contraction of GCP by Ca2+ buthad no effect if ABA was also present with Ca2+. The inhibitionof swelling of GCP by Ca2+ was also prevented by the presenceof lanthanum or verapamil (another Ca2+ channel blocker). These results indicate that Ca2+ and ABA can act independentlyof each other in contracting swollen GCP and in preventing K+-inducedswelling of contracted GCP of C. communis. If swelling and contractionof GCP are equivalent to stomatal opening and closure, respectively,the results do not support the hypothesis that ABA opens Ca2+channels in the plasma membrane of guard cells allowing Ca2+to enter the cells and, as a second messenger, to set in motionclosing processes. Key words: Abscisic acid, calcium, guard cell protoplasts, stomata 相似文献
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Eight samples of dried tomato soups were profiled by a trained panel, who also provided ratings of overall liking and liking for particular attributes on relative-to-ideal rating scales. A consumer panel tested a subset of four of the soups in home trials, assessing them for overall liking and for particular attributes on either hedonic or relative-to-ideal rating scales. The pattern of overall preferences differed between the trained and untrained panelists, demonstrating the inappropriateness of using trained panelists to provide measures of preference or acceptance. The conclusions regarding consumer preferences would differ depending on which rating scale was used; these differences disappeared when the relative-to-ideal ratings were converted into values of the same form as the hedonic ratings. The overall liking was best predicted by flavor rather than color or thickness. A principal components analysis (PCA) of the profile data compared well with a plot based on the trained panel preference data using MDPREF. The preference data were also fitted to the PCA dimensions using the PREMAP vector model, which gave a good fit for only six of the 15 trained panelists; the PREMAP ideal point model failed to show a better fit. In order to test these models adequately more than eight samples would need to be tested. 相似文献
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J. L. VAN HOUTEN R. SMITH J. WYMER B. PALMER M. DENARO 《The Journal of eukaryotic microbiology》1985,32(4):613-616
Normal Paramecium tetraurelia cells stained with fluorescein-conjugated folate show intense fluorescence that can be reduced to near background autofluorescence with excess K2-folate, but not with excess KCl. Mutant d4–534, which is not attracted to folate and does not specifically bind 3H-folate, shows reduced fluorescence when stained. This method of monitoring specific folate binding to cells can be adapted to a microscale for rapid screening of clones since cells are routinely fixed and stained in microtiter wells. 相似文献
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The rates of sulphate transport into intact and excised rootsof soybean (Glycine max L.) were not significantly differentin the first hour and were maximal at pH 7. However, intactroots accumulated four times as much sulphate as excised rootsin 24 h, because of a marked reduction in the rate of transportby excised roots. The continued high rates of transport intointact roots were observed in plants kept in the light, andobserved in darkened plants growing in 1 per cent sucrose. Similarly,sulphate accumulation by excised roots was stimulated 2-foldby 1 per cent sucrose. The characteristics of sulphate accumulation by roots were notuseful in predicting sulphate translocation to the leaves. Transportto the leaves was maximal at pH 23, was almost totallylight-dependent and was not enhanced by growing plants in sucrose. Sulphate transport, Glycine max L., soybean, excised roots 相似文献
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THE QUANTITATIVE STUDY OF MYCORRHIZAL INFECTION 总被引:10,自引:9,他引:1
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The effect of changes in the environment on lipid metabolismhas been studied in the brown alga, Fucus serratus L. Lightstimulated the incorporation of radioactivity from /{I4C/}acetateinto oleic and, especially, into linoleic acid. The same effectwas caused by lowering the incubation temperature from 15 °Cto 4 °C. Incubations in the presence of Cd + +, Pb + + orZn+ + had no effect on the total uptake of /{14C/}acetate intothe frond tip samples, but lowered the labelling of total lipidsrelative to aqueous-soluble components. However, pre-exposureof the algae to heavy metal cations caused changes in the uptakeof radioactivity but had less effect on the relative labellingof lipids than incubations in the presence of heavy metal cations.Algae collected from sites where the dissolved levels of heavymetals were elevated, showed a decrease in the relative labellingof lipids from /{14C/}acetate. Concentrations of Cd+ +, Pb++ or Zn+ + at 10 x levels found at the collection site had littleeffect on the pattern of fatty acids made by Fucus serratus. Key words: Lipid metabolism, Fucus serratus L., Environmental changes 相似文献