Plant Physiology

Jung, Dennis W.; Laties, George G.

doi: 10.1104/pp.63.4.591pmid: 16660774

Abstract The uptake of [14C]citrate and [14C]succinate was studied in potato mitochondria (Solanum tuberosum var. Russet Burbank) using cellulose pore filtration and was found to occur by the same mechanisms as described for mammalian mitochondria. Potato mitochondria, in the absence of respiration, have a very low capacity for uptake by exchange with endogenous anions, taking up only 2.4 nanomoles citrate and 2.0 nanomoles succinate per milligram protein. Maximum citrate uptake of over 17 nanomoles per milligram protein occurs in the presence of inorganic phosphate, a dicarboxylic acid, and an external energy source (NADH), conditions where net anion accumulation proceeds, mediated by the interlinking of the inorganic phosphate, dicarboxylate, and tricarboxylate carriers. Maximum succinate uptake in the absence of respiratory inhibitors requires only added inorganic phosphate. Compounds which inhibit respiration (antimycin), the exchange carriers (mersalyl and benzylmalonate), or the establishment of the membrane proton motive force (uncouplers) reduce substrate accumulation. A potent inhibitor of the citrate carrier in animal mitochondria, 1,2,3-benzenetricarboxylic acid, does not inhibit citrate uptake in potato mitochondria. Citrate uptake is reduced by concurrent ADP phosphorylation and this reduction is sensitive to oligomycin. The initiation of state 3 after a 3-minute substrate state results in a reduction of the steady-state of citrate uptake by approximately 50%. Accumulation of succinate initially is inhibited by increasing sucrose concentration in the reaction medium from 50 to 400 millimolar. Limited substrate uptake is one of the factors responsible for the often observed depressed initial state 3 respiration rates in many mitochondrial preparations. Since nonlimiting levels of substrate in the matrix cannot be attained by energy-independent exchange, a dependence on respiration for adequate uptake results. Substrate limitation therefore occurs in the matrix for the period of time needed for energy-dependent accumulation of nonlimiting levels. 2 Present address: Department of Physiological Chemistry, Ohio State University, Columbus, Ohio 43210. 1 This work was supported by Energy Research and Development Administration Grant EY-76-S-03-0034. This content is only available as a PDF. © 1979 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Finkle, Bernard J.; Ulrich, Jane M.

doi: 10.1104/pp.63.4.598pmid: 16660775

Abstract Cryoprotection of suspension cultures of sugarcane cells (Saccharum sp.) during freezing to various temperatures was tested using glucose, dimethylsulfoxide, and ethylene glycol at various concentrations, alone and in combinations. Viability of the thawed cells was assessed by triphenyltetrazolium chloride reduction, cell growth, and microscopic examination. Enhanced cryoprotection—as much as a doubling in viability value—was achieved by employing glucose and dimethylsulfoxide in mixtures, as compared with the lesser cryoprotective effect of either compound alone, at 1.9 molar total concentration in all cases; the mixture was most effective at a concentration of about 1.9 molar, with a molar ratio of the two components of about 1:3, respectively. Much of the increase in viability value arose from a decrease in toxic effect that came about through mixing the cryoprotective agents. Binary mixtures containing ethylene glycol and either glucose or dimethylsulfoxide were less effective and more toxic than comparable glucose-dimethylsulfoxide mixtures. Use of the optimized latter mixture allowed freezing of these tropical cells to −23 C with little decrease in survival, or to −40 C, still with the capability for delayed growth. This content is only available as a PDF. © 1979 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Laasch, Norbert; Kaiser, Werner; Urbach, Wolfgang

doi: 10.1104/pp.63.4.605pmid: 16660776

Abstract The effects of disalicylidenepropanediamine (DSPD) and disulfo-disalicylidenepropanediamine (sulfo-DSPD) on the photosynthetic electron transport of isolated chloroplasts have been reexamined. Our data suggest that DSPD, but not sulfo-DSPD, is an effective inhibitor of electron transport between photosystem II and photosystem I before or at plastocyanin. Furthermore, both DSPD and sulfo-DSPD block electron transport at the site of ferredoxin. Under certain conditions DSPD and even more so sulfo-DSPD function as autooxidizable electron acceptors. Finally it is shown that DSPD can cause an inhibition of photophosphorylation. According to our results the use of DSPD as a specific inhibitor of ferredoxin-dependent reactions has to be questioned. This content is only available as a PDF. © 1979 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Aloni, Roni

doi: 10.1104/pp.63.4.609pmid: 16660777

Abstract The hypothesis that auxin and gibberellic acid (GA3) control the differentiation of primary phloem fibers is confirmed for the stem of Coleus blumei Benth. Indoleacetic acid (IAA) alone sufficed to cause the differentiation of a few primary phloem fibers. In long term experiments auxin induced a considerable number of fibers in mature internodes. GA3 by itself did not exert any effect on fiber differentiation. Combinatiosn of IAA with GA3 completely replaced the role of the leaves in primary phloem fiber differentiation qualitatively and quantitatively. Although the combined effect of the two growth hormones diminished considerably with increasing distance from the source of induction, auxin with GA3 or IAA alone induced fibers in a few internodes below the application site. When various combinations of both hormones were applied, high concentrations of IAA stimulated rapid differentiation of fibers with thick secondary walls, while high levels of GA3 resulted in long fibers with thin walls. The size of the primary phloem fibers correlated with the dimensions of the differentiating internode, thereby providing evidence that both growth regulators figure in the control of stem extension. High IAA/low GA3 concentrations have an inhibitory effect on internode elongation, whereas low IAA/high GA3 concentrations promote maximal stem elongation. 1 Supported in part by the Lady Davis Fellowship Trust. This content is only available as a PDF. © 1979 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Gantt, Elisabeth; Lipschultz, Claudia A.; Grabowski, Joseph; Zimmerman, Burke K.

doi: 10.1104/pp.63.4.615pmid: 16660778

Abstract A general procedure for the isolation of functionally intact phycobilisomes was devised, based on modifications of previously used procedures. It has been successful with numerous species of red and blue-green algae (Anabaena variabilis, Anacystis nidulans, Agmenellum quadruplicatum, Fremyella diplosiphon, Glaucosphaera vacuolata, Griffithsia pacifica, Nemalion multifidum, Nostoc sp., Phormidium persicinum, Porphyridium cruentum, P. sordidum, P. aerugineum, Rhodosorus marinus). Isolation was carried out in 0.75 molar K-phosphate (pH 6.8 to 7.0) at 20 to 23 C on sucrose step gradients. Lower temperature (4 to 10 C) was usually unfavorable resulting in uncoupling of energy transfer and partial dissociation of the phycobilisomes, sometimes with complete loss of allophycocyanin. Intact phycobilisomes were characterized by fluorescence emission peaks of 670 to 675 nanometers at room temperature, and 678 to 685 nanometers at liquid nitrogen temperature. Uncoupling and subsequent dissociation of phycobilisomes, in lowered ionic conditions, varied with the species and the degree of dissociation but occurred preferentially between phycocyanin and allophycocyanin, or between phycocyanin and phycoerythrin. 2 Present address: Institute of Physics, Poznań Technical University, Piotrowo 3, 60-965, Poznań, Poland. 1 This research was supported in part by the Department of Energy Contract EY-76-S-05-4310, the Smithsonian Board of Academic Studies by granting a fellowship to J. Grabowski, and the Smithsonian Institution. This content is only available as a PDF. © 1979 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Cheruel, Jacqueline; Jullien, Marc; Surdin-Kerjan, Yolande

doi: 10.1104/pp.63.4.621pmid: 16660779

Abstract The uptake of threonine, aspartic acid, and isoleucine into cultivated asparagus cells was examined under culture conditions. Transport was linear with time and with the number of cells present in the assay. The upake of the three amino acids obeyed Michaelis-Menten kinetics with apparent affinities in the range of 0.1 to 0.02 millimolar. Azide and 2,4-dinitrophenol caused inhibition of threonine uptake. Reciprocal competitive inhibitions were found between threonine, aspartic acid, and isoleucine. Methionine and lysine competitively inhibited the uptake of these three amino acids. These results and the comparison of apparent affinities and inhibition constants are in favor of only one uptake system for threonine, aspartic acid, isoleucine, methionine, and lysine with different affinities for the different amino acids. All other amino acids with the exception of histidine, arginine, asparagine, and hydroxyproline inhibited threonine uptake. It is most likely that at least one component of the uptake system is shared by all amino acids. 1 This investigation was helped by a grant from the Commissariat à l'Energie Atomique, France. This content is only available as a PDF. © 1979 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Gusta, Lawrence V.; Fowler, David Brian; Chen, Paul; Russell, David B.; Stout, Darryl G.

doi: 10.1104/pp.63.4.627pmid: 16660780

Abstract Continuous wave nuclear magnetic resonance (NMR) studies indicated that the line width of the water absorption peak (Δv½) from crowns of winter and spring wheat (Triticum aestivum L.) increased during cold acclimation. There was a negative correlation between Δv½ and crown water content, and both of these parameters were correlated with the lowest survival temperature at which 50% or more of the crowns were not killed by freezing (LT50). Regression analyses indicated that Δv½ and water content account for similar variability in LT50. Slow dehydration of unacclimated winter wheat crowns by artificial means resulted in similarly correlated changes in water content and Δv½. Rapid dehydration of unacclimated crowns reduced water content but did not influence Δv½. The incubation of unacclimated winter wheat crowns in a sucrose medium reduced water content and increased Δv½. The increase in Δv½ appears to be dependent in part on a reduction in water content and an increase in solutes. Longitudinal (T1) and transverse (T2) relaxation times of water protons in cereals at different stages of cold acclimation were measured using pulse NMR methods. The T1 and T2 signals each demonstrated the existence of two populations of water, one with a short and one with a long relaxation time. During the first 3 weeks of acclimation, the long T2 decreased significantly in winter-hardy cereals, and did not change in a spring wheat until the 5th week of hardening. There was no change in the long T1 until the 3rd week of hardening for the winter cereals and until the 7th week of hardening for the spring wheat. No simple relationship could be established between T1 or T2 and cold hardiness. Neither continuous wave or pulsed NMR spectroscopy can be used as a diagnostic tool in predicting the cold hardiness of winter wheats. An increase in Δv½ or a reduction in relaxation times does not provide evidence for ordering of the bulk of the cell water. 2 Present address: Agriculture Canada, Range Research Station, 3015 Ord Road, Kamloops, B.C., Canada, V2B 8A9. 1 Research was supported in part by the National Research Council of Canada Grant A-9661. This content is only available as a PDF. © 1979 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Abou-Khalil, Samir; Hanson, John B.

doi: 10.1104/pp.63.4.635pmid: 16660781

Abstract Corn shoot mitochondria possess an energy-linked transport system for sulfate uptake as demonstrated by osmotic swelling and [35S]SO42− accumulation. Maximum uptake is secured in the presence of Mg2+ and oligomycin with sucrose for osmotic support. Neither phosphate nor dicarboxylate anions are required. When added simultaneously, millimolar concentrations of phosphate block [35S]SO42− uptake after the initial minute. Mersalyl, N-ethylmaleimide, and 2,4-dinitrophenol are strong inhibitors of sulfate uptake; n-butylmalonate is a weak inhibitor. These inhibitors act in the same fashion on phosphate uptake. It is concluded that sulfate uptake in the absence of phosphate is by the phosphate transporter. 1 This research was supported by United States Department of Energy Grant EY-76-S-02-0790. This content is only available as a PDF. © 1979 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Schilling, Norbert; Kende, Hans

doi: 10.1104/pp.63.4.639pmid: 16660782

Abstract Stem sections of etiolated pea seedlings (Pisum sativum L. cv. Alaska) were incubated overnight on tracer amounts of l-[U-14C]methionine and, on the following morning, on 0.1 millimolar indoleacetic acid to induce ethylene formation. Following the overnight incubation, over 70% of the radioactivity in the soluble fraction was shown to be associated with S-methylmethionine (SMM). The specific radioactivity of the ethylene evolved closely paralleled that of carbon atoms 3 and 4 of methionine extracted from the tissue and was always higher than that determined for carbon atoms 3 and 4 of extracted SMM. Overnight incubation of pea stem sections on 1 millimolar methionine enhanced indoleacetic acid-induced ethylene formation by 5 to 10%. Under the same conditions, 1 millimolar homocysteine thiolactone increased ethylene synthesis by 20 to 25%, while SMM within a concentration range of 0.1 to 10 millimolar did not influence ethylene production. When unlabeled methionine or homocysteine thiolactone was applied to stem sections which had been incubated overnight in l-[U-14C]methionine, the specific radioactivity of the ethylene evolved was considerably lowered. Application of unlabeled SMM reduced the specific radioactivity of ethylene only slightly. 2 Present address: Botanisches Institut der Universität München, Menzingerstr. 67, D-8 Munich, Federal Republic of Germany. 1 This research was supported by the United States Energy Research and Development Administration and the Department of Energy under Contract EY-76-C-02-1338, and by the National Science Foundation through Grant PCM 77-08522. N. Schilling received partial support from the Deutsche Forschungsgemeinschaft. This content is only available as a PDF. © 1979 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Ogawa, Yukiyoshi; King, Roderick W.

doi: 10.1104/pp.63.4.643pmid: 16660783

Abstract Benzyladenine (BA) brushed on the cotyledons of 4-day-old seedlings of Pharbitis nil Chois. markedly stimulates flowering. Greates response is obtained for concentrations between 44 and 440 micromolar. The action of BA is on processes in the cotyledon as shown by the response to its site of application, to the dosage applied and to the requirement for its application prior to the dark period. There was little or no effect of BA treatment on either the time measurement processes of photoperiodic induction or on the generation of floral stimulus. Transport of photosynthetic assimilate from the cotyledons to the shoot apex was altered. When only one of the pair of cotyledons was treated with BA it exported less 14C-labeled assimilate to the shoot apex and there was a compensatory increase in assimilate outflow from the other cotyledon. When BA was applied to a cotyledon exposed to an inductive dark period, flowering was inhibited in association with the reduced export of assimilate. Conversely, when BA was applied to the noninduced cotyledon, flowering was promoted in association with an enhanced export of assimilate from the induced leaf. Clearly, cytokinins can have an indirect effect on photoperiodic induction by altering assimilate and, hence, floral stimulus translocation to the shoot apex. Two other chemicals which were previously considered as specific inhibitors of processes of floral induction in the cotyledon [Tris(2-diethylaminoethyl)phosphate trihydrochloride (SK&F 7997-A3) and cycloheximide] acted in the same manner as BA. Inhibitory effects of an illuminated cotyledon on flowering of Pharbitis were also shown to be mediated by interference of assimilate flow with transport of the stimulus for flowering. 1 Present address: Faculty of Agriculture, Mie University, Tsu City, Mie Prefecture, Japan. This content is only available as a PDF. © 1979 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)