PLANT PHYSIOLOGY

Hall, A. E.; Loomis, R. S.

doi: 10.1104/pp.50.5.576pmid: 16658220

Abstract Sugar beets (Beta vulgaris L.) infected with the Beet Yellows Virus exhibit lower rates of net photosynthesis at light saturation than do healthy plants. These Pn reductions were correlated with increases in leaf resistance to water vapor loss. Theoretical analyses demonstrated that, although the leaf resistance to water vapor loss increases could account for a major part of the net photosynthesis decreases, some other aspect of leaf functioning also was debilitated by infection. Both the levels and the activities of ribulose-1, 5-diP carboxylase were less on a leaf area basis in extracts from infected leaves than from healthy ones. Soluble carbohydrates accumulate in Beet Yellows Virus-infected leaves, but inhibiting translocation in several ways provided no evidence in support of the hypothesis that the accumulation of photosynthates in leaves has a direct, short term, feed-back effect upon the photosynthetic rate. 2 Present address: Department of Plant Sciences, University of California, Riverside, California 92502. 1 This investigation was partially supported by a grant from a cooperative agreement with the United States Department of Agriculture (No. 21-14-100-5630-34). This content is only available as a PDF. © 1972 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)

Davies, Eric; Larkins, Brian A.; Knight, Robert H.

doi: 10.1104/pp.50.5.581pmid: 16658221

Abstract Profiles of polyribosomes were obtained from etiolated stem segments of Pisum sativum L. var. Alaska isolated in various buffers. Tissue homogenized in a medium containing 0.2 m tris-HCl, pH 8.5, 0.2 m sucrose, 30 mm MgCl2, and 60 mm KCl yielded polyribosomes exhibiting far less degradation than tissue homogenized in conventional media containing tris-HCl at lower ionic strength and pH. A further decrease in degradation was found when polyribosomes were sedimented through a sucrose pad buffered at pH 8.5 prior to centrifugation. Increased separation was obtained using heavy (125-500 mg/ml), linear sucrose gradients. Using these techniques, messenger RNA species bearing up to 12 ribosomes (dodecamers) were resolved, with messenger RNA chains bearing 9 ribosomes (nonamers) being the most abundant (having the highest absorption peak). The data presented suggest that buffer of high ionic strength and high pH was more effective in preventing degradation of polyribosomes than was diethyl pyrocarbonate and, furthermore, that ratios involving large polyribosomes (hexamers and larger) were more accurate indices of degradation than were ratios involving total polyribosomes. 1 This research was supported in part by a Biomedical Sciences Support Grant RT-07055 through the University of Nebraska Research Council, and a National Science Foundation Fellowship to B.A.L. This content is only available as a PDF. © 1972 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)

Rudich, J.; Halevy, A. H.; Kedar, N.

doi: 10.1104/pp.50.5.585pmid: 16658222

Abstract The endogenous levels of auxin, gibberellin, and inhibitors were followed in monoecious and gynoecious cucumber (Cucumis sativus L.) plants, and in plants treated with the ethylene-releasing compound Ethephon (2-chloroethyl phosphonic acid). Higher auxin inhibitor and lower gibberellin levels were associated with female tendency. The endogenous level of gibberellin and auxin decreased in Ethephon-treated plants. Application of Ethephon induced a rise in abscisic acid. Root application of abscisic acid promoted female tendency of gynoecious cucumbers grown under conditions which increase maleness. High CO2 levels, which are known to antagonize ethylene, increased maleness of gynoecious cucumbers. The possibility of interrelationship between gibberellin, auxin, ethylene, and abscisic acid on sex expression are discussed. 1 This paper represents a part of the Ph.D. thesis of J. Rudich. This content is only available as a PDF. © 1972 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)

Miles, C. D.

doi: 10.1104/pp.50.5.591pmid: 16658223

Abstract When spinach (Spinacia oleracea) chloroplast fragments were lyophilized and extracted with n-heptane, acid-bath phosphorylation was significantly reduced. Phosphorylation could be restored to these chloroplasts, if the extracted material (containing quinones, carotenoids, and other lipids) was added back to dry preparation before rehydration. The results reported suggest it was not quinones which were required for restoration of acid-bath phosphorylation but lipids. It is suggested that the lipids which were extracted by n-heptane serves as structural role in the thylakoid membrane. This content is only available as a PDF. © 1972 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)

Moore, Thomas S.; Miller, Carlos O.

doi: 10.1104/pp.50.5.594pmid: 16658224

Abstract A technique which incorporates a brief blending step to disperse callus tissue into small clumps of cells was developed, and the effects of cytokinins on respiration of soybean (Glycine max [L.] Merrill var. Acme) callus tissue prepared in this way were studied. Adenine alone did not affect respiration, but kinetin and zeatin showed effects correlating with their reported effects on growth of this tissue; after about 3 hours both hormones promoted respiration at concentrations which promote growth, while kinetin, but not zeatin, also exhibited inhibition at higher concentrations. Studies with 2,4-dinitrophenol led to the suggestion that although the respiration of this tissue is largely under the control of ATP levels, kinetin does not exert its control on respiration through effects on ATP levels or oxidative phosphorylation during the monitoring period. Further inhibitor and substrate studies provided evidence that the promotion of respiration by kinetin results from an increase in substrate entering the tricarboxylic acid cycle, perhaps by an effect on pyruvate metabolism. The inhibition of respiration by high concentrations of kinetin is partially due to effects on oxidative phosphorylation or ATP utilization, but 70% of the inhibition cannot be attributed to this. 2 Present address: Division of Natural Sciences I, University of California, Santa Cruz, Calif. 95060. 1 This research was supported in part by a Public Health Services fellowship to T. M. and National Science Foundation Grant GB 12115. This content is only available as a PDF. © 1972 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)

Engelsma, G.

doi: 10.1104/pp.50.5.599pmid: 16658225

Abstract Divalent Mn ions cause an increase in the level of phenylalanine ammonia-lyase in gherkin hypocotyls. With the exception of Mg ions, which had a small effect, no other metal ion has so far been found which could replace the Mn ion in this respect. Invertase and peroxidase were not significantly affected by the Mn treatment. The increase in phenylalanine ammonialyase activity is explained by the removal, under the influence of Mn ions, of hydroxycinnamic acids, which cause repression of phenylalanine ammonia-lyase synthesis and/or inactivation of phenylalanine ammonia-lyase. Arguments are advanced for the hypothesis that photochemical transformations of Mn complexes are involved in the photoinduction of phenylalanine ammonia-lyase in dark-grown gherkin seedlings. This content is only available as a PDF. © 1972 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)

Gerson, Donald F.; Poole, Ronald J.

doi: 10.1104/pp.50.5.603pmid: 16658226

Abstract Net uptake of Cl− into root tips of mung bean (Phaseolus aureus) increases steadily with increasing external concentrations from 1 to 60 mm. Membrane potentials were measured to determine the equilibrium concentration of Cl− in the tissue which could be due to diffusion. This concentration was readily exceeded in both the relatively nonvacuolate tips (0 to 1 mm) and the vacuolate, mature upper sectons (1 to 11 mm) of the roots. The activity coefficient of both cytoplasmic and vacuolar Cl−, measured with Cl− sensitive microelectrodes, was approximately the same as that of a pure KCl solution of the same concentration. It is concluded that the “second mechanism” of ion uptake involves a large increase in the rate of active transport at the plasmalemma as the external concentration is increased above 1 mm. 2 Present address: Department of Biophysics, University of Western Ontario, London 72, Ontario, Canada. 1 This work was supported by a grant from the National Research Council of Canada. This content is only available as a PDF. © 1972 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)

Lee, O. Y.; Stadelmann, Ed. J.; Weiser, C. J.

doi: 10.1104/pp.50.5.608pmid: 16658227

Abstract Decenylsuccinic acid altered permeability to water of epidermal cells of bulb scales of Allium cepa and of the leaf midrib of Rhoeo discolor. Water permeability, as determined by deplasmolysis time measurements, was related to the dose of undissociated decenylsuccinic acid (mm undissociated decenylsuccinic acid × minute). No relationship was found between permeability and total dose of decenylsuccinic acid, or dose of dissociated decenylsuccinic acid, suggesting that the undissociated molecule was the active factor in permeability changes and injury. At doses which did not damage cells (0.0008 to 0.6 [mm of the undissociated molecule × minute]) decenylsuccinic acid decreased water permeability. At higher doses (e.g., 4 to 8 [mm × minute]) injury to cells was common and decenylsuccinic acid increased permeability. Doses above the 10 to 20 (mm × minute) range were generally lethal. The plasmolysis form of uninjured cells was altered and protoplasmic swelling occasionally was observed. The dose-dependent reversal of water permeability changes (decreased to increased permeability) may reflect decenylsuccinic acid-induced changes in membrane structure. Reported effects of decenylsuccinic acid on temperature dependence of permeability and frost resistance were not verified. 1 This research was supported by a grant from the Lois W. and Maud Hill Family Foundation and the Minnesota Agricultural Experiment Station. Minnesota Agricultural Experiment Station Scientific Journal Series Paper No. 7716. This content is only available as a PDF. © 1972 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)

Dyson, W. H.; Hall, R. H.

doi: 10.1104/pp.50.5.616pmid: 16658228

Abstract Cytokinins from both the free nucleoside pool and the transfer RNA have been isolated and identified in a habituated strain of tobacco pith callus (Nicotiana tabacum [L] var. Wisconsin 38). The transfer RNA of this strain contains both N6-(Δ2-isopentenyl) adenosine and N6-(4-hydroxy-3-methylbut-2-cis-enyl) adenosine. The trans-hydroxylated derivative is absent from the transfer RNA of this dark-grown tissue. N6-(Δ2-Isopentenyl)-adenosine was identified as a component of the free nucleoside pool in concentrations of about 10 micrograms per kilogram of tissue. The cytokinin-requiring tissue grown in the presence of N6-furfurylaminopurine contains less than 85 nanograms per kilogram of N6-(Δ2-isopentenyl) adenosine. This is the detectable limit under the conditions of the experiment. 1 This work was supported by a grant from the Canadian Cancer Society. 2 A preliminary report of this work was presented at the 1971 American Society of Plant Physiologists meeting, Asilomar, Calif. This content is only available as a PDF. © 1972 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)

Waller, G. R.; Skursky, L.

doi: 10.1104/pp.50.5.622pmid: 16658229

Abstract Ricinine-3,5-14C (N-methyl-3-cyano-4-methoxy-2-pyridone) administered to senescent leaves of Ricinus communis L. was translocated to all other tissues of the plant. Developing fruit and especially seeds were found to be labeled the most rapidly. Young growing leaves and other developing tissues of the plant imported ricinine from the senescent leaves much more quickly than mature leaves. Relative intensities of the radioactive ricinine imported and deposited in various tissues indicate a possible functional role of ricinine in the castor bean plant. Data on N-demethyl ricinine presented here may stimulate interest in the possible physiological role of the ricinine to N-demethyl ricinine interconversion. 2 Present address: Department of Biochemistry, Faculty of Science, University J. E. Purkyné, Brno, Czechoslovakia. 1 Journal Article No. 2500 of the Agricultural Experiment Station, Oklahoma State University, Stillwater, Okla. This research was supported in part by research grant GM-08624 from the National Institutes of Health, Bethesda, Md. This content is only available as a PDF. © 1972 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)