Plant Physiology

Owens, L. D.; Lieberman, M.; Kunishi, A.

doi: 10.1104/pp.48.1.1pmid: 16657720

Abstract Rhizobitoxine, an inhibitor of methionine biosynthesis in Salmonella typhimurium, inhibited ethylene production about 75% in light-grown sorghum seedlings and in senescent apple tissue. Ethylene production stimulated by indoleacetic acid and kinetin in sorghum was similarly inhibited. With both apple and sorghum, the inhibition could only be partially relieved by additions of methionine. A methionine analogue, α-keto-γ-methylthiobutyric acid, which has been suggested as an intermediate between methionine and ethylene, had no effect on the inhibition. Incorporation of 14C from added methionine-14C into ethylene was curtailed by rhizobitoxine to about the same extent as was ethylene production. These results suggest that rhizobitoxine interferes with ethylene biosynthesis by blocking the conversion of methionine to ethylene and not indirectly by inhibiting the biosynthesis of methionine. Ethylene production by Penicillium digitatum, a fungus which produces ethylene via pathways not utilizing methionine as a precursor, was not affected by rhizobitoxine. This content is only available as a PDF. © 1971 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)

Mantai, K. E.; Hind, G.

doi: 10.1104/pp.48.1.5pmid: 16657732

Abstract Hydrazine can support a rapid oxygen uptake in illuminated chloroplasts. The oxygen uptake rate is inhibited by 3-(3,4-dichlorophenyl)-1, 1-dimethylurea but is only slightly increased by added methyl viologen, and little H2O2 is produced. The pH optimum for hydrazine-dependent oxygen uptake is much higher than that of the Hill reaction. Addition of Mn (II) increases the rate of oxygen uptake in the light and causes the reaction to continue in the dark, the dark rate being dependent on the duration of the preceding light period. Flash yield experiments show that at least six electrons are transferred from hydrazine per flash compared to one electron per flash when water is the electron donor. We conclude that most of the oxygen uptake in the presence of hydrazine is due to a direct oxidation of the hydrazine by oxygen which is catalyzed by some factor, possibly Mn (III), produced by chloroplasts in the light. Other artificial electron donors are shown to support such artefactual oxygen uptake to varying extents. 2 Present address: Department of Biology, State University College, Fredonia, N. Y. 14063. 1 Research carried out at Brookhaven National Laboratory under the auspices of the United States Atomic Energy Commission. This content is only available as a PDF. © 1971 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)

Jensen, R. G.; Francki, R. I. B.; Zaitlin, M.

doi: 10.1104/pp.48.1.9pmid: 16657742

Abstract Suspensions of mesophyll cells, prepared from tobacco leaves by treatment with pectinase, fixed CO2 by photosynthesis. The products of carbon assimilation were similar for both cells and intact tissue. The cells sustained a constant fixation rate for 20 to 25 hours. For optimal CO2 fixation, enzymatic maceration of the tissue was accomplished in 0.8 m sorbitol, but photosynthesis was optimal in 0.6 m sorbitol at pH 7 to 7.5. A hypertonic environment during maceration, which results in cell plasmolysis, is essential to maintain intact plasmalemmas and hence photosynthetically active cells. For sustained CO2 fixation, light intensities below 500 foot-candles were required. Higher light intensities (to 1000 foot-candles) gave high initial rates of CO2 fixation, but the cells bleached and were inactive on prolonged incubation. At pH 7.0 the bicarbonate concentration at maximal velocity of CO2 fixation was about 1.5 mm and the apparent Km for bicarbonate was 0.2 mm. 2 On leave from the Department of Plant Pathology, Waite Agricultural Research Institute, University of Adelaide, South Australia, and supported in part by the Australian-American Educational Foundation. 1 This work was supported in part by Grants GB 27453 and GB 25873 from the National Science Foundation, by Atomic Energy Commission Contract AT (11-1)-873, and by the Agricultural Division, Monsanto Company. The University of Arizona Agricultural Experiment Station Journal Paper 1731. This content is only available as a PDF. © 1971 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)

Francki, R. I. B.; Zaitlin, M.; Jensen, R. G.

doi: 10.1104/pp.48.1.14pmid: 16657725

Abstract Enzymatically separated tobacco leaf cells took up amino acids, uracil, and uridine from the incubation medium and incorporated them into proteins and RNA, respectively, at a linear rate for approximately 30 hours. Both uptake and incorporation were light-dependent, although cells prepared from preilluminated plants or preillumination of cells allowed some uptake and incorporation to occur in the dark. The light was necessary to satisfy a photosynthetic requirement, but could be replaced in part by ATP in the medium. Several lines of evidence support the conclusion that the rate of uptake of amino acids, uracil, and uridine was dependent upon the subsequent incorporation of these compounds into macromolecules. 2 On leave from the Department of Plant Pathology, Waite Agricultural Research Institute, University of Adelaide, South Australia. Supported in part by the Australian-American Educational Foundation. 1 This work was supported by Grants GB 25873 and GB 27453 from the National Science Foundation, by Atomic Energy Commission Contract AT (11-1)-873, and by the Agricultural Division, Monsanto Co. University of Arizona Agricultural Experiment Station Journal Paper 1732. This content is only available as a PDF. © 1971 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)

Wong, Thomas C.; Luh, Bor S.; Whitaker, John R.

doi: 10.1104/pp.48.1.19pmid: 16657726

Abstract The polyphenol oxidase system in clingstone peach (Prunus persica) was investigated. Polyacrylamide disc-gel electrophoresis indicated four bands with polyphenol oxidase activity in extracts from acetone powder of clingstone peach. These four isozymes were then isolated from a buffer extract of peach acetone powder by cold acetone precipitation, followed by diethylaminoethyl cellulose column chromatography. All isozymes had different heat stabilities. At 55 C, polyphenol oxidases A, B, and D had half-lives of 5.4, 14.6, and 14.1 minutes, respectively. Polyphenol oxidase C was stable over a period of 50 minutes of incubation at 55 C, but had a half-life of 2.2 minutes at 76 C. None of the isozymes had monophenolase activity, and they varied in their specificity for several diphenols. The following values were found for polyphenol oxidases A, B, C, and D, respectively, with catechol as substrate: optimal pH: 6.8, 6.5, 7.2, and 7.0; Michaelis constant: 6.6, 4.2, 7.0, and 36 mm; V max/(E 0): 4.95, 39.4, 2.16, and 80.0 (ΔA min−1 mg−1). Each isozyme showed a different amount of inhibition by NaHSO3, NaCl, NaCN, l-ascorbic acid, glutathione, ethylenediaminetetraacetate, and sodium diethyldithiocarbamate. 2 Present address: Research Laboratory, E. & J. Gallo Winery, Modesto, Calif. 1 This investigation was supported in part by Training Grants UI-01053 and F & D-00008 from the United States Public Health Service. Taken from the dissertation submitted by Thomas C. Wong to the Graduate Division, University of California, Davis, in partial satisfaction of the requirements for the Ph.D. degree. This content is only available as a PDF. © 1971 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)

Wong, Thomas C.; Luh, Bor S.; Whitaker, John R.

doi: 10.1104/pp.48.1.24pmid: 16657727

Abstract Phloroglucinol and resorcinol are not substrates for clingstone peach (Prunus persica) polyphenol oxidase, but they react with 4-methyl-o-quinone, produced either enzymatically or nonenzymatically, to give an intense red or red-brown color with a maximal absorption at about 470 nanometers. Several colored products were isolated from an ethyl acetate extract of the reaction by two-dimensional thin layer chromatography. Based on thin layer chromatographic and spectral studies of the enzymatic and nonenzymatic reactions, polyphenol oxidase does not play a role in the reaction between 4-methyl-o-quinone and phloroglucinol, resorcinol, d-catechin, or orcinol. In such reactions, the function of polyphenol oxidase is the formation of 4-methyl-o-quinone which then reacts nonenzymatically with the above phenols. Activation energies of both enzymatic and nonenzymatic reactions were determined. 2 Present address: Research Laboratory, E. & J. Gallo Winery, Modesto, California. 1 This investigation was supported in part by Training Grants UI-01053 and F & D-00008 from the United States Public Health Service. Taken from the dissertation submitted by Thomas C. Wong to the Graduate Division, University of California, Davis, in partial satisfaction of the requirements for the Ph.D. degree. This content is only available as a PDF. © 1971 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)

Shih, C. Y.; Rappaport, Lawrence

doi: 10.1104/pp.48.1.31pmid: 16657728

Abstract Using the electron microscope, we compared the effects of abscisic acid and gibberellin A3 on excised buds from resting potato (Solanum tuberosum L.) tubers. Cells of abscisic acid-treated buds became progressively more vacuolated during a 12-hour time course study as compared with control (water) and gibberellin A3-treated buds. Concentric configurations of endoplasmic reticulum were present in apical cells of freshly excised buds. After about 6 hours these configurations began to open and disperse, and after 12 hours, intact concentric configurations were no longer evident. Both abscisic acid and gibberellin A3 induced opening and dispersal of the concentric configurations, sometimes as early as 0.5 hour after excision and treatment with hormones. 1 Present address: Department of Botany, University of Iowa, Iowa City, Iowa. This content is only available as a PDF. © 1971 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)

Roberts, R. M.; Heishman, A.; Wicklin, C.

doi: 10.1104/pp.48.1.36pmid: 16657729

Abstract The growth of corn (Zea mays) roots and barley (Hordeum vulgare) coleoptiles is sensitive to the presence of external d-glucosamine and d-galactose. In order to investigate this effect, tissues were fed the radioactive monosaccharides at concentrations that ranged from those that were strongly inhibitory to those that had little influence on growth. At low concentrations, d-glucosamine is converted to uridine diphosphate-N-acetyl-d-glucosamine, phosphate esters of N-acetylglucosamine, and free N-acetylglucosamine. As the external concentrations were increased, the pool levels of each of these metabolites rose several fold; and, in corn roots, two unidentified compounds, which had not been detected previously, began to accumulate in the tissues. The major products of d-galactose metabolism were uridine diphosphate-d-galactose and d-galactose 1-phosphate at all the concentrations tested. Both these compounds showed a marked increase as the external galactose concentrations were raised to inhibitory levels. The experiments indicate that efficient pathways exist in plants for the metabolism of d-glucosamine and d-galactose. These pathways, however, do not appear to be under strict control, so that metabolites accumulate in unusually high amounts and presumably interfere competitively with normal carbohydrate metabolism. This content is only available as a PDF. © 1971 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)

Leffler, H. R.; O'Brien, T. J.; Glover, D. V.; Cherry, J. H.

doi: 10.1104/pp.48.1.43pmid: 16657730

Abstract Chromatin isolated from soybean (Glycine max L., var. Wayne) hypocotyls was capable of catalyzing the polymerization of labeled deoxyribonucleoside triphosphate in the presence of the three other deoxyribonucleoside triphosphates into a trichloroacetic acid-insoluble product. This product was insensitive to base hydrolysis and ribonuclease, but was sensitive to acid hydrolysis and deoxyribonuclease. Chromatin-DNA polymerase required Mg2+ and all four deoxyribonucleoside triphosphates for maximal activity. Inorganic pyrophosphate and actinomycin D inhibited the polymerase activity, but 2, 4-dichlorophenoxyacetic acid had no effect in vitro. Chromatin from plants previously treated with 2, 4-dichlorophenoxyacetic acid supported a greater level of DNA synthesis than did chromatin from untreated plants. 2 Present address: Department of Agronomy, University of Illinois, Urbana, Ill. 61801. 3 Present address: Allan Hancock Foundation, Department of Biological Sciences, University of Southern California, Los Angeles, Calif. 90007. 1 Purdue University Agriculture Experiment Station Journal Paper 4304. Taken in part from a dissertation submitted by the senior author to the Graduate School of Purdue University in partial fulfillment of the requirements for the Ph.D. degree. This content is only available as a PDF. © 1971 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)

McArthur, James A.; Briggs, Winslow R.

doi: 10.1104/pp.48.1.46pmid: 16657731

Abstract Reversion of far red-absorbing phytochrome to red-absorbing phytochrome without phytochrome destruction (that is, without loss of absorbancy and photoreversibility) occurs in the following tissues of etiolated Alaska pea seedlings (Pisum sativum L.): young radicles (24 hours after start of imbibition), young epicotyls (48 hours after start of imbibition), and the juvenile region of the epicotyl immediately subjacent to the plumule in older epicotyls. Reversion occurs rapidly in the dark during the first 30 minutes following initial phototransformation of red-absorbing phytochrome to far red-absorbing phytochrome. If these tissues are illuminated continuously with red light for 30 minutes, the total amount of phytochrome remains unchanged. Beyond 30 minutes after a single phototransformation or after the start of continuous red irradiation, phytochrome destruction commences. In young radicles, sodium azide inhibits this destruction, but does not affect reversion. In older tissues in which far red-absorbing phytochrome destruction begins immediately upon phototransformation, strong evidence for simultaneous far red-absorbing phytochrome reversion is obtained from comparison of far red-absorbing phytochrome loss in the dark following a single phototransformation with far red-absorbing phytochrome loss under continuous red light. 2 Present address: Department of Botany, North Carolina State University, Raleigh, N. C. 27607. 1 This work was supported in part by National Science Foundation Grants GB-2846 and GB-6683, and a grant from Research Corporation to W.R.B. This content is only available as a PDF. © 1971 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)