Plant Physiology

Randy Moore and John Pasieniuk

doi: N/Apmid: N/A

Levi, Carolyn; Gibbs, Martin

doi: 10.1104/pp.74.3.459pmid: 16663444

Abstract The activities of amylase and phosphorylase were monitored during the 12-hour light/dark synchronous cell cycle of autotrophically grown Chlamydomonas reinhardtii 11-32/90. The activity of amylase increased from 7.3 to 42 micromole reducing equivalents per 109 cells per hour while phosphorylase increased from 43 to 214 micromole glucose 1-phosphate released per 109 cells per hour between the midlight and middark periods. Cellular fractionation indicated that both enzymes were localized solely within the chloroplast. The pH optima for amylase and phosphorylase were 6.7 to 7.6 and 6.0 to 7.4, respectively. The amylase is a heat-labile α-amylase which is insensitive to ethylenetetraaecetate but inhibited by N-ethylmaleimide. 2 Present address: Department of Plant Pathology, University of Wisconsin—Madison, 1630 Linden Drive, Madison, WI 53706. 1 Supported by National Science Foundation PCM 79-22612. This content is only available as a PDF. © 1984 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)

Tyerman, Stephen D.; Steudle, Ernst

doi: 10.1104/pp.74.3.464pmid: 16663445

Abstract The analysis of Sha'afi et al. (Sha'afi, Rich, Mickulecky, Solomon 1970 J Gen Physiol 55: 427-450) for determining solute permeability in red blood cells has been modified and applied to turgid plant cells. Following the addition of permeating solute to the external medium, a biphasic response of cell turgor can be measured with the pressure probe in isolated internodes of Chara corallina. After an initial decrease in turgor due to water flow (water phase), turgor increases due to the uptake of the solute (solute phase) until the original turgor is reattained. From the pressure/time course in the neighborhood of the minimum turgor, the permeability of the osmotic solute can be determined. The data obtained by the minimum method for rapidly permeating (ethanol, methanol) and slowly permeating (formamide, dimethylformamide) solutes are similar to those calculated from the half-time of pressure changes during the solute phase and to data obtained by other workers using radioactive tracers. The methods employing the pressure probe were applied to examine the effect of high pH (up to pH 11) on the membrane permeability. There appeared to be no effect of high pH on the permeability coefficients, reflection coefficients, and hydraulic conductivity. 2 Present address: School of Biological Sciences, The Flinders University of South Australia, Bedford Park, South Australia, 5042, Australia. 1 Supported by a grant from the Deutsche Forschungsgemeinschaft, Zi 99/8. This content is only available as a PDF. © 1984 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)

Galloway, Ruth E.; Mets, Laurens J.

doi: 10.1104/pp.74.3.469pmid: 16663446

Abstract A series of Chlamydomonas reinhardii mutants were selected for resistance to the herbicides atrazine, bromacil, and diuron. Four of these have reduced herbicide binding to the thylakoid membranes and show the non-Mendelian inheritance pattern characteristic of chloroplast genes. These mutants show a variety of selective alterations in binding of the three herbicides. These changes account for the observed patterns of in vivo cross-resistance. Analyses of chloroplast gene recombination indicate that these four mutations are in the same gene. Overall, the results suggest that this gene codes for a protein component of the herbicide binding site. One of the mutants has slow phototrophic growth and altered electron transport as has been observed in atrazine-resistant higher plant varieties, but the others are normal in these respects. The slow growth characteristic of this mutant seems to be the consequence of the same mutation which confers herbicide resistance. The mutants isolated also include a large number which achieve resistance by some secondary mechanism. These are all nuclear gene mutations, and represent numerous loci. They also show a variety of patterns of cross-resistance, but the mechanisms behind them have not yet been investigated. 1 Supported by National Science Foundation Grant PCM 80-22722. This content is only available as a PDF. © 1984 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)

Mirecki, Roman M.; Teramura, Alan H.

doi: 10.1104/pp.74.3.475pmid: 16663447

Abstract Soybeans (Glycine max [L.] Merr. cv Essex) were grown in a green-house, and the first trifoliate leaf was either allowed to expand under a high photosynthetic photon flux density (PPFD) (1.4 millimoles per square meter per second) or a low PPFD (0.8 millimoles per square meter per second). After full leaf expansion, plants from each treatment were placed into a factorial design experiment with two levels of ultraviolet-B (UV-B) radiation (0 and 80 milliwatts per square meter biologically effective UV-B) and two levels of concomitant PPFD (0.8 and 1.4 millimoles per square meter per second) resulting in a total of eight treatments. Measurements of net photosynthesis and the associated diffusion conductances, ribulose-1,5-bisphosphate carboxylase activity, chlorophyll and flavonoid concentrations, and leaf anatomy were examined for all treatments. Leaves expanded in the high PPFD were unaffected by UV-B radiation while those expanded in the low PPFD were sensitive to UV-B-induced damage. Likewise, plants which were UV-B irradiated concomitantly with the high PPFD were resistant to UV-B damage, while plants irradiated under the low PPFD were sensitive. The results of this study indicate that both anatomical/morphological and physiological/biochemical factors contribute toward plant sensitivity to UV-B radiation. 1 Supported partially by the United States Environmental Protection Agency's Environmental Research Laboratory in Corvallis, OR (CR 808-035-020) and grants from the Graduate School and Provost to A. H. T. Scientific Article No. A-3397. Contribution No. 6470, of the Maryland Agricultural Experiment Station, Department of Botany. Although the work described in this article has been funded in part by the United States Environmental Protection Agency, it has not been subjected to the Agency's required peer and policy review and therefore does not necessarily reflect the view of the Agency and no official endorsement should be inferred. This content is only available as a PDF. © 1984 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)

Mawson, Bruce T.; Franklin, Angus; Filion, W. Gary; Cummins, W. Raymond

doi: 10.1104/pp.74.3.481pmid: 16663448

Abstract The chlorophyll fluorescence induction curves from mesophyll and guard cell chloroplasts of Saxifraga cernua, including both the fast (O to P, the transients involved in the rise in variable fluorescence) and slow (P to steady state fluorescence due to quenching) components, were characterized over a range of excitation intensities using microspectrophotometry (with epi-lumination) equipped with apertures designed to eliminate cross contamination of the fluorescence signal between the two chloroplast types. At low excitation intensities, the fast fluorescence kinetics from guard cell plastids showed an extended I to D phase and a more rapid appearance of P while minimal quenching from P to steady state fluorescence was observed compared to the transients from mesophyll chloroplasts suggesting a lower activity of photochemical (electron movement via carriers between donor and acceptor sites) and nonphotochemical (such as membrane conformational changes) events which regulate the fluorescence induction curve kinetics. As the excitation intensity was increased, the quenching rates of guard cells were faster at initiating conditions for photophosphorylation and the fast and slow fluorescence kinetics from guard cells resembled those of the mesophyll cells. Guard cell chloroplasts of S. cernua from intact epidermal peels showed a low temperature (77 K) fluorescence emission spectrum having three major peaks (at 685, 695, and 730 nanometers when excited at 440 nanometers) which were qualitatively similar to those in the spectrum obtained from mesophyll tissue. These data suggest that S. cernua guard cell chloroplast photosystems I and II contribute to light-dependent stomatal activity only at high light intensities. 1 Supported by grants from the Natural Sciences and Engineering Research Council of Canada, the Atkinson Charitable Foundation, Northern Scientific Training Grants Program of the Canada Department of Indian and Northern Affairs, and the Donner Canadian Foundation. This content is only available as a PDF. © 1984 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)

Laroche, Monique; Aspart, Lorette; Delseny, Michel; Penon, Paul

doi: 10.1104/pp.74.3.487pmid: 16663449

Abstract Radish (Raphanus sativus cv Rond rose à bout blanc Vilmorin) seeds, as other cruciferae oil seeds, contain two major types of storage protein aggregates which can be separated by gel filtration into 12 and 1.7 Svedberg fractions. These two fractions have been characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, amino acid composition, and two bidimensional gel electrophoresis systems. These results were compared with those obtained with rapeseed storage proteins. Radish 12 Svedberg particles are made of a series of nine major polypeptides ranging from 33 to 30 kilodaltons. These polypeptides present charge heterogeneity. The 12 Svedberg particle is made of six subunits ≃ 55 kilodaltons. Each subunit is a couple of two polypeptides linked by a disulfide bridge. The 1.7 Svedberg particle has a simpler composition. It is made of two polypeptides of 10 and 12 kilodaltons and smaller peptides of ≃ 7 kilodaltons. Twelve and 1.7 Svedberg particles also differ in their amino acid composition, the 1.7 Svedberg being particularly rich in glutamic acid and proline. Its components are basic. The organization of the rapeseed storage protein is similar but more complex. 1 Supported by CNRS E.R.A. 226 and in part by a grant from the Ministry of Research and Industry (M. L.). This content is only available as a PDF. © 1984 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)

Nielsen, S. Suzanne; Liener, Irvin E.

doi: 10.1104/pp.74.3.494pmid: 16663450

Abstract Cotyledons from Phaseolus vulgaris L. (var. Improved Tendergreen) were tested for their activity on α-N-benzoyl-dl-arginine-p-nitroanilide (BAPNA) and azocasein during a germination periood of 10 days. Both activities increased throughout germination when activity was expressed on the basis of dry weight or protein. That these two activities were most likely due to the action of different enzymes was indicated by the fact that (a) optimal pH for the hydrolysis of BAPNA and azocasein was 8.2 and 5.5, respectively, and (b) the digestion of azocasein was considerably enhanced by mercaptoethanol and partially inhibited by thiol protease inhibitors, N-ethylmaleimide, and E-64, whereas these same regents caused little change in activity toward BAPNA. The three subunits of the major storage protein, G1, disappeared during germination and were accompanied by the accumulation of lower molecular weight products. The breakdown of G1 by extracts of the germinated beans could be demonstrated in vitro at pH 5 to 6. This activity was enhanced by mercaptoethanol and completely abolished by N-ethylmalemide, leupeptin, and E-64. It is concluded that a thiol protease with an acid pH optimum is primarily responsible for the disappearance of the major storage protein during germination. Although an inhibitor of the plant thiol protease, papain, is present in the mature bean and decreases during germination, its role in the control of the breakdown of the storage protein remains to be elucidated. 2 Present address: Department of Food Science, Purdue University, West Layfayette, IN 47907. 1 This work was supported by United States Public Health Service Grant AM 18324. This content is only available as a PDF. © 1984 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)

Pate, John S.; Peoples, Mark B.; Atkins, Craig A.

doi: 10.1104/pp.74.3.499pmid: 16663451

Abstract The vasculature of the dorsal suture of cowpea (Vigna unguiculata [L.] Walp) fruits bled a sugar-rich exudate when punctured with a fine needle previously cooled in liquid N2. Bleeding continued for many days at rates equivalent to 10% of the estimated current sugar intake of the fruit. A phloem origin for the exudate was suggested from its high levels (0.4-0.8 millimoles per milliliter) of sugar (98% of this as sucrose) and its high K+ content and high ratio of Mg2+ to Ca2+. Fruit cryopuncture sap became labeled with 14C following feeding of [14C]urea to leaves or adjacent walls of the fruit, of 14CO2 to the pod gas space, and of [14C] asparagine or [14C]allantoin to leaflets or cut shoots through the xylem. Rates of translocation of 14C-assimilates from a fed leaf to the puncture site on a subtended fruit were 21 to 38 centimeters per hour. Analysis of 14C distribution in phloem sap suggested that [14C]allantoin was metabolized to a greater extent in its passage to the fruit than was [14C] asparagine. Amino acid:ureide:nitrate ratios (nitrogen weight basis) of NO3-fed, non-nodulated plants were 20:2:78 in root bleeding xylem sap versus 90:10:0.1 for fruit phloem sap, suggesting that the shoot utilized NO3-nitrogen to synthesize amino acids prior to phloem transfer of nitrogen to the fruit. Feeding of 15NO3 to roots substantiated this conclusion. The amino acid:ureide ratio (nitrogen weight basis) of root xylem sap of symbiotic plants was 23:77 versus 89:11 for corresponding fruit phloem sap indicating intense metabolic transfer of ureide-nitrogen to amino acids by vegetative parts of the plant. 1 Supported by funds from the Australian Research Grants Scheme and the Wheat Industry Research Council of Australia. This content is only available as a PDF. © 1984 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)

Ericson, Mary C.; Alfinito, Sharon H.

doi: 10.1104/pp.74.3.506pmid: 16663452

Abstract The protein pattern of cultured tobacco (Nicotiana tabacum L. var Wisconsin 38) cells that have become adapted to a medium containing 10 grams NaCl per liter was compared to that of unadapted cells on one-dimensional sodium dodecyl sulfate gels. Two protein bands (32,000 and 20,000 daltons) were much more abundant in the salt-adapted cells, and one protein (26,000 daltons) was unique to the salt cells. This protein pattern did not change during the growth cycle of the cells. When salt-adapted cells are transferred to control medium, their ability to grow in the salt-containing medium returns to that of control cells after one passage in the control medium (Hasegawa, Bressan, Handa 1980 Plant Cell Physiol 21: 1347). Within this time the levels of the 32,000 and 20,000 dalton proteins also return to that of the control cells, but the 26,000 dalton protein does not disappear until after at least two passages in control medium. Amino acid analyses of these three proteins revealed that they all contain some hydroxyproline. This content is only available as a PDF. © 1984 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)