Plant Physiology

Saltveit, Mikal E.; McFeeters, Roger F.

doi: 10.1104/pp.66.6.1019pmid: 16661568

Abstract Polygalacturonase (EC 3.2.1.15) activity in seed cavity tissue from harvested cucumber fruit increased over 20-fold after the fruit had produced a transient burst of ethylene during maturation. This increase was observed in six cucumber cultivars and was present whether polygalacturonase activity was measured at pH 4.6 or 6.2. The seed cavity tissue pH decreased as polygalacturonase activity increased both in ripening fruit and in harvested immature fruit exposed to 10 microliters per liter ethylene in air. 2 United States Department of Agriculture, Science and Education Administration, AR, Southern Region, and North Carolina Agricultural Research Service, Department of Food Science, North Carolina State University, Raleigh, NC 27650. 1 This is paper No. 6299 of the Journal series of the North Carolina Agricultural Research Service, Raleigh, North Carolina. The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service, or by the United States Department of Agriculture of products named, nor criticism of similar ones not mentioned. This content is only available as a PDF. © 1980 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)

Gorton, Holly L.; Briggs, Winslow R.

doi: 10.1104/pp.66.6.1024pmid: 16661569

Abstract Corn seedlings were grown in white light in the absence and presence of the chlorosis-inducing herbicide San 9789. The resulting green and achlorophyllous seedlings were used to investigate phytochrome-mediated responses to end-of-day far red irradiation and reversal of these responses by subsequent red irradiation. Mesocotyl and coleoptile elongation increased in response to end-of-day far red irradiation, whereas the anthocyanin content of the coleoptiles was decreased. All three responses were reversible by red irradiation following the far red. Dose-response curves for far red induction and red reversal of these responses did not differ significantly for plants grown in the presence or absence of San 9789. Thus, San 9789 appears to affect neither phytochrome itself nor the response system involved. Chlorophyll screening likewise does not affect phytochrome relationships for these responses. 1 Carnegie Institution of Washington publication 695. This content is only available as a PDF. © 1980 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)

Bhuvaneswari, T. V.; Turgeon, B. Gillian; Bauer, Wolfgang D.

doi: 10.1104/pp.66.6.1027pmid: 16661570

Abstract The infectible cells of soybean roots appear to be located at any given time just above the zone of root elongation and just below the position of the smallest emergent root hairs. The location of infectible cells on the primary root at the time of inoculation was inferred from the position of subsequent nodule development, correcting for displacement of epidermal cells due to root elongation. Marks were made on the seedling growth pouches at the time of inoculation to indicate the position of the root tip and the zones of root hair development. Virtually all of the seedlings developed nodules on the primary root above the marks made at the root tips at the time of inoculation. None of the plants formed nodules on the root where mature root hairs were present at the time of inoculation. These results and profiles of nodulation frequency indicate that the location of infectible cells is developmentally restricted. When inoculations were delayed for intervals of 1 to 4 hours after marking the positions of the root tips, progressively fewer nodules were formed above the root tip marks, and the uppermost of these nodules were formed at progressively shorter distances above the marks. These results indicate that the infectibility of given host cells is a transient property that appears and then is lost within a few hours. The results also indicate that host responses leading to infection and nodulation are triggered or initiated in less than 2 hours after inoculation. The extent of nodulation above the root tip mark increased in proportion to the logarithm of the number of bacteria in the inoculum. 2 To whom reprint requests should be addressed. 1 This work was supported in part by grant PCM 77-24930 from the National Science Foundation. This is contribution No. 709 of the C. F. Kettering Research Laboratory. This content is only available as a PDF. © 1980 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)

Gerbaud, Alain; André, Marcel

doi: 10.1104/pp.66.6.1032pmid: 16661571

Abstract Unidirectional O2 fluxes were measured with 18O2 in a whole plant of wheat cultivated in a controlled environment. At 2 or 21% O2, O2 uptake was maximum at 60 microliters per liter CO2. At lower CO2 concentrations, it was strongly inhibited, as was photosynthetic O2 evolution. At 2% O2, there remained a substantial O2 uptake, even at high CO2 level; the O2 evolution was inhibited at CO2 concentrations under 330 microliters per liter. The O2 uptake increased linearly with light intensity, starting from the level of dark respiration. No saturation was observed at high light intensities. No significant change in the gas-exchange patterns occurred during a long period of the plant life. An adaptation to low light intensities was observed after 3 hours illumination. These results are interpreted in relation to the functioning of the photosynthetic apparatus and point to a regulation by the electron acceptors and a specific action of CO2. The behavior of the O2 uptake and the study of the CO2 compensation point seem to indicate the persistence of mitochondrial respiration during photosynthesis. This content is only available as a PDF. © 1980 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)

Booz, Martha L.; Travis, Robert L.

doi: 10.1104/pp.66.6.1037pmid: 16661572

Abstract The polypeptide complement of enriched soybean (Glycine max [L.] Merr. cult. wells) root plasma membrane fractions was studied by two-dimensional gel electrophoresis. Good resolution was obtained when polypeptides were solubilized in sodium dodecyl sulfate and when butylated hydroxytoluene was included in the vesicle isolation and solubilization media. The pattern obtained on the two-dimensional slab gel for root plasma membrane was characteristic for that membrane. The polypeptide complements from mitochondrial membranes and from enriched fractions of three other endomembrane components were solubilized and electrophoresed for comparison. Each membrane preparation was identifiable on the basis of its characteristic electrophoretogram. Electrophoresis of protein solubilized from plasma membrane fractions isolated from meristematic and mature root tissue revealed both qualitative and quantitative differences in the respective protein complements. 1 This work was supported in part by a fellowship (to M. L. B.) from the Association for Women in Science. This content is only available as a PDF. © 1980 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)

Varner, Joseph E.; Burton, Jane E.

doi: 10.1104/pp.66.6.1044pmid: 16661573

Abstract Simple methods are described for following in vivo the rate of peptidylproline hydroxylation and for determining what proportion of the total proline incorporated into protein is hydroxylated. 1 This work was supported by National Science Foundation Grant PCM 76-14178. This content is only available as a PDF. © 1980 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)

Upadhyaya, Mahesh K.; Noodén, Larry D.

doi: 10.1104/pp.66.6.1048pmid: 16661574

Abstract The intracellular binding of dinitroaniline herbicides was studied in order to analyze the mechanism of their colchicine-like action. When corn root apices (5 millimeters) are incubated in [14C]oryzalin (a dinitroaniline herbicide), the 14C is taken up rapidly, reaching a plateau in about 4 hours, which corresponds to the minimum incubation time in oryzalin required to get maximum inhibition of elongation. At 4 hours, the [14C]oryzalin concentration inside the roots is 35 times higher than that in the incubation medium. Since this accumulation of [14C]oryzalin is not affected by 1 millimolar sodium azide and there is no metabolism of [14C]oryzalin under these conditions, the [14C]oryzalin must be accumulated (bound) in corn root apices by a process not requiring metabolic energy. Molecular sieve chromatography (Sephadex G-200) does not show any binding of [14C]oryzalin to any protein with molecular weight similar to the microtubule-subunit protein in rat brain or corn root extracts. However, a massive binding of [14C]oryzalin occurs in the insoluble fraction of corn root extracts. This binding is not localized in any particle size range, is not affected by sonication, is of high capacity, and is a loose (low affinity) association with the binding sites. These binding sites could be solubilized with membrane detergents, which suggests that oryzalin may bind to cellular membranes. Since boiling the homogenate does not affect [14C]oryzalin binding, oryzalin more likely binds to a lipid rather than a protein component of cellular membranes. 2 Present address: Departments of Biology and Crop Science, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N OWO. 1 This work was supported in part by the Division of Biological Sciences, Cancer Research Institute, the Horace H. Rackham School of Graduate Studies of the University of Michigan, and Lilly Research Laboratory, Greenfield, Indiana. This content is only available as a PDF. © 1980 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)

Saglio, Pierre H.; Raymond, Philippe; Pradet, Alain

doi: 10.1104/pp.66.6.1053pmid: 16661575

Abstract Energy charge and fermentative metabolism under anoxia were monitored in excised maize root tips after various times of aging in air and were related to their soluble sugar content. The energy charge value, which was 0.9 in air irrespective of the time of aging, dropped to a lower value within minutes of transfer to a nitrogen atmosphere. This value was dependent upon sugar content of the tissues which was itself a function of aging. The energy charge value after transfer to nitrogen was 0.6 in freshly excised tissue but only 0.2 in tissue aged for 4 hours. When aged tissues supplied with 0.2 molar glucose were transferred to nitrogen, the energy charge was 0.6, irrespective of the time of aging. When 0.2 molar glucose was added under nitrogen, energy charge rose to 0.6. This rise was faster in root tips aged for 8 hours than those aged for 24 hours. The rate of ethanol plus lactate production (representing 60 and 10%, respectively, of the total sugar consumption in anoxia) was closely correlated to the level of energy charge. It is concluded that, in anoxia, there is a quantitative relationship between the energy charge value and the level of metabolic activity via fermentative pathways. This content is only available as a PDF. © 1980 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)

Chin, Chee-Kok; Lee, Michael

doi: 10.1104/pp.66.6.1058pmid: 16661576

Abstract Inhibition of respiration of cultured cells of Petunia hybrida by NaF, NaN3, malonic acid, and salicylhydroxamic acid increased at low pH. This increase could be partially reversed by raising the pH of the medium. Uptake experiments show that the greater inhibition of malonic acid at low pH was not the result of greater uptake. The results suggest that the increase in inhibition at low pH could not be attributed to greater cell penetration. 1 This work was supported by the New Jersey Agricultural Experiment Station and performed as part of New Jersey Argricultural Experiment Station project 12403. This content is only available as a PDF. © 1980 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)

Emerich, David W.; Ruiz-Argüeso, Tomas; Russell, Sterling A.; Evans, Harold J.

doi: 10.1104/pp.66.6.1061pmid: 16661577

Abstract The H2-oxidizing complex in Rhizobium japonicum 122 DES bacteroids failed to catalyze, at a measurable rate, 2H1H exchange from a mixture of 2H2 and 1H2 in presence of 2H2O and 1H2O, providing no evidence for reversibility of the hydrogenase reaction in vivo. In the H2 oxidation reaction, there was no significant discrimination between 2H2 and 1H2, indicating that the initial H2-activation step in the over-all H2 oxidation reaction is not rate-limiting. By use of improved methods, an apparent K m for H2 of 0.05 micromolar was determined. The H2 oxidation reaction in bacteroids was strongly inhibited by cyanide (88% at 0.05 millimolar), theonyltrifluoroacetone, and other metal-complexing agents. Carbonyl cyanide m-chlorophenylhydrazone at 0.005 millimolar and 2,4-dinitrophenol at 0.5 millimolar inhibited H2 oxidation and stimulated O2 uptake. This and other evidence suggest the involvement of cytochromes and nonheme iron proteins in the pathway of electron transport from H2 to O2. Partial pressures of H2 at 0.03 atmosphere and below had a pronounced inhibitory effect on endogenous respiration by bacteroid suspensions. The inhibition of CO2 evolution by low partial pressures of H2 suggests that H2 utilization may result in conservation of oxidizable substrates and benefits the symbiosis under physiological conditions. Succinate, acetate, and formate at concentrations of 50 millimolar inhibited rates of H2 uptake by 8, 29, and 25%, respectively. The inhibition by succinate was noncompetitive and that by acetate and formate was uncompetitive. A concentration of 11.6 millimolar CO2 (initial concentration) in solution inhibited H2 uptake by bacteroid suspensions by 18%. Further research is necessary to establish the significance of the inhibition of H2 uptake by succinate, acetate, formate, and CO2 in the metabolism of the H2-uptake-positive strains of Rhizobium. 2 Supported by a postdoctoral fellowship from the Rockefeller Foundation and by Postdoctoral Fellowship SPI 78-15650 from the National Science Foundation. Present address: Department of Biochemistry, University of Missouri-Columbia, Columbia, MO 65211. 3 Supported by the Program of Cultural Cooperation between the United States and Spain. Present address: Departamento de Microbiologia, Escuela Tecnica Superior de Ingenieros Agronomos, Madrid-3, Spain. 1 This research was supported in part by Grant PCM 77-08784 from the National Science Foundation and by the Oregon Agricultural Experiment Station, from which this is Technical Paper No. 5217. This content is only available as a PDF. © 1980 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)