Plant Physiology

Kaufmann, Merrill R.; Eckard, Alan N.

doi: 10.1104/pp.47.4.453pmid: 16657642

Abstract The water relations of pepper plants (Capsicum frutescens L.) under conditions conducive to guttation were studied to evaluate the control of plant water stress with polyethylene glycols. The addition of polyethylene glycol 6000 to the nutrient solution resulted in water relations similar to those expected in soil at the same water potentials. Specifically, xylem pressure potential in the root and leaf became more negative during a 24-hour treatment period, while osmotic potential of the root xylem sap remained constant. The decrease in pressure potential was closely correlated with the decrease in osmotic potential of the nutrient solution. In contrast, the addition of polyethylene glycol 400 to the nutrient medium resulted in a reduction of osmotic potential in the root xylem sap; this osmotic adjustment in the xylem was large enough to establish an osmotic gradient for entry of water and cause guttation at a nutrient solution osmotic potential of −4.8 bars. Pressure potential in the root and leaf xylem became negative only at nutrient solution osmotic potentials lower than −4.8 bars. About half of the xylem osmotic adjustment in the presence of polyethylene glycol 400 was caused by increased accumulation of K+, Na+, Ca2+, and Mg2+ in the root xylem. These studies indicate that larger polyethylene glycol molecules such as polyethylene glycol 6000 are more useful for simulating soil water stress than smaller molecules such as polyethylene glycol 400. 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)

De Greef, J.; Butler, W. L.; Roth, T. F.

doi: 10.1104/pp.47.4.457pmid: 16657643

Abstract Eight-day-old dark-grown bean leaves were greened by prolonged irradiation with far red light. Growth, chlorophyll content, oxygen-evolving capacity, photophosphorylation capacity, chloroplast structure (by electron microscopy), and in vivo forms of chlorophyll (by low temperature absorption and derivative spectroscopy on intact leaves) were followed during the greening process. Chlorophyll a accumulated slowly but continuously during the 7 days of the experiment (each day consisted of 12 hours of far red light and 12 hours of darkness). Chlorophyll b was not detected until the 5th day. The capacity for oxygen evolution and photophosphorylation began at about the 2nd day. Electron microscopy showed little formation of grana during the 7 days but rather unfused stacks of primary thylakoids. The thylakoids would fuse to give grana if the leaves were placed subsequently in white light. The low temperature spectroscopy of intact leaves showed that the chlorophyll a was differentiated into three forms with absorption maxima near 670, 677, and 683 nanometers at −196 C during the first few hours and that these forms accumulated throughout the greening process. Small amounts of two longer wavelength forms with maxima near 690 and 698 nanometers appeared at about the same time as photosynthetic activity. 1 Present address: Rijksuniversitair Centrum Antwerpen, Laboratory of General Botany, Groenenborgerlaan 171, 2020 Antwerpen, Belgium. 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)

Ohad, Itzhak; Friedberg, Ilan; Ne'Eman, Zvi; Schramm, Michael

doi: 10.1104/pp.47.4.465pmid: 16657644

Abstract Storage of mature or developing potato tubers (Solanum tuberosum “Up-to-Date” variety) at 4 C causes a reduction in the starch content and the elevation in the level of free sugars. This phenomenon is not observed when the tubers are stored at 25 C. Changes in the morphology of cells from developing or mature tubers after storage at 4 or 25 C have been followed by electron microscopy. During all stages of the tuber development the starch granules are surrounded by a membrane derived from the plastid envelope. Storage in the cold induces disintegration of this membrane. A membrane fraction isolated from starch granules of tubers stored at 4 C has a lower buoyant density, and the electrophoretic pattern of its proteins is different from that of a similar membrane fraction obtained from tubers stored at 25 C. It is suggested that the cold-induced changes in the starch and sugar content during storage of potato tubers might be correlated with damage to the membranes surrounding the starch granules and changes in their permeability to degradative enzymes and substrates. 1 Supported by United States Department of Agriculture grant FG-Is-280 to M. Schramm and I. Ohad. 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)

Curtis, Roy W.

doi: 10.1104/pp.47.4.478pmid: 16657645

Abstract Malformin completely inhibited Ethrel-induced swelling and fresh weight increase on the basal stem portion of Phaseolus vulgaris L. cuttings, but markedly potentiated Ethrel- or ethylene-induced abscission. With regard to abscission, malformin reacted synergistically with ethylene and dark aging, and in a manner which appeared to differ from that of ethylene and dark aging. The numerous effects of malformin on plant growth and development cannot be explained in simple terms of enhanced ethylene production. 1 Research supported by National Science Foundation Grant GB-7158. Purdue University AES Journal Paper 4078. 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)

Miura, George A.; Mills, Stanley E.

doi: 10.1104/pp.47.4.483pmid: 16657646

Abstract d-Tryptophan was converted to l-tryptophan in tissue cultures of tobacco, in whole cells treated with dimethylsulfoxide, and in cell-free extracts treated by Sephadex G-25 filtration. Evidence was obtained that tryptophanase, tryptophan pyrrolase, and transaminase activities were not involved. The data were best explained by the presence of a tryptophan racemase as the enzyme catalyzing the reaction. The possible role of d-tryptophan in the biosynthesis of indoleacetic acid is discussed. 2 Present address: Department of Biochemistry, McMaster University, Hamilton, Ontario, Canada. 1 This investigation was supported by Contract AT(11-1)-34 from the 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)

Ketring, D. L.; Morgan, P. W.

doi: 10.1104/pp.47.4.488pmid: 16657647

Abstract Germination, ethylene production, and carbon dioxide production by dormant Virginia-type peanuts were determined during treatments with plant growth regulators. Kinetin, benzylaminopurine, and 2-chloroethylphosphonic acid induced extensive germination above the water controls. Benzylaminopurine and 2-chloroethylphosphonic acid increased the germination of the more dormant basal seeds to a larger extent above the controls than the less dormant apical seeds. Coumarin induced a slight stimulation of germination while abscisic acid, 2,4-dichlorophenoxyacetic acid, and succinic acid 2,2-dimethylhydrazide did not stimulate germination above the controls. In addition to stimulating germination, the cytokinins also stimulated ethylene production by the seeds. In the case of benzylaminopurine, where the more dormant basal seeds were stimulated to germinate above the control to a larger extent than the less dormant apical seeds, correspondingly more ethylene production was induced in the basal seeds. However, the opposite was true of kinetin for both germination and ethylene production. When germination was extensively stimulated by the cytokinins, maximal ethylene and carbon dioxide evolution occurred at 24 and 72 hours, respectively. Abscisic acid inhibited ethylene production and germinaton of the seeds while carbon dioxide evolution was comparatively high. The crucial physiological event for germination of dormant peanut seeds was enhancement of ethylene production by the seeds. 1 Cooperative investigations of the Plant Science Research Divison, Agricultural Research Service, United States Department of Agriculture and the Texas Agricultural Experiment Station, Texas A&M University. 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)

Shannon, Leland M.; Uritani, Ikuzo; Imaseki, Hidemasa

doi: 10.1104/pp.47.4.493pmid: 16657648

Abstract The peroxidase content of sweet potato slices (Ipomoea batatas Lam.) increased nearly 100-fold following 84 hours incubation in an air atmosphere containing ethylene, 1 microliter per liter. The object of experiments reported here is to determine if this increase in peroxidase activity results from synthesis de novo of the enzyme or from activation of a preexisting inactive form of the enzyme. The enzymatic activity of each peroxidase isozyme increased during the incubation period, and each peroxidase isozyme appeared to incorporate 14C-leucine. Polyacrylamide gel electrophoresis of the neutral peroxidase fraction showed that all peroxidase activity and essentially all radioactivity migrated as a single superimposable band. The other peroxidase fractions were less pure. Treatment of fresh slices, or slices collected midway in the time course with the inhibitor of protein synthesis, blasticidin S, (1 microgram per milliliter for one minute) caused an abrupt cessation of peroxidase formation and simultaneously an abrupt cessation of incorporation of 14C-leucine into peroxidase isozymes. These observations indicate that the rapid increase in peroxidase activity in sweet potato slices results from synthesis de novo of the enzyme. 3 Present address: Biochemistry Department, University of California, Riverside, California 92502. 4 Present address: Institute for Biochemical Regulation, Faculty of Agriculture, Nagoya University, Nagoya, Japan. 1 This research was supported in part by the National Science Foundation and the Japan Society for the Promotion of Science through an award of a Visiting Scientist Grant under the auspices of the United States-Japan Cooperative Science Program. 2 This paper constitutes Part 89 of the Phytopathological Chemistry of Sweet Potato with Black Rot and Injury. 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)

Tautvydas, Kestutis J.

doi: 10.1104/pp.47.4.499pmid: 16657649

Abstract Improvements in conventional filtration and centrifugation procedures made it possible to increase the yield of intact cytoplasm-free pea (Pisum sativum) nuclei from the usual 3 to 10% to 32% (6 × 108 nuclei per 7 grams fresh weight of pea apices) and to complete the isolation in 80 to 90 minutes. The isolated nuclei appeared to retain their structural integrity as revealed in electron photomicrographs, and remained intact for at least 5 hours at 20 Celsius. The DNA:RNA: protein ratio of isolated pea nuclei was found to be 3.1:1:9.9. Their RNA polymerase activity, monitored by incorporation of 14C into RNA from 14C-UTP, was linear for about 10 minutes, and then gradually declined over the next 15 to 20 minutes. 1 The author was aided by a Title IV NDEA fellowship. This represents a portion of a thesis submitted to the Graduate School at Yale University in 1969, in partial fulfillment of the requirements for a Ph.D. degree. 2 Present address: Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado 80302. 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)

Kang, Bin G.; Newcomb, William; Burg, Stanley P.

doi: 10.1104/pp.47.4.504pmid: 16657650

Abstract Indoleacetic acid-induced ethylene production and growth in excised segments of etiolated pea shoots (Pisum sativum L. var. Alaska) parallels the free indoleacetic acid level in the tissue which in turn depends upon the rate of indoleacetic acid conjugation and decarboxylation. Both ethylene synthesis and growth require the presence of more than a threshold level of free endogenous indoleacetic acid, but in etiolated tissue the rate of ethylene production saturates at a high concentration and the rate of growth at a lower concentration of indoleacetic acid. Auxin stimulation of ethylene synthesis is not mediated by induction of peroxidase; to the contrary, the products of the auxin action which induce growth and ethylene synthesis are highly labile. 2 Present address: Department of Biology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada. 1 This work was supported by the National Science Foundation Grant GB-8322 to S. P. Burg. 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)

Givan, Curtis V.; Stumpf, P. K.

doi: 10.1104/pp.47.4.510pmid: 16657651

Abstract In the biosynthesis of fatty acids from 1-14C-acetate by intact spinach chloroplasts, ATP and Triton X-100 exert opposing effects on the conversion of palmitic acid to stearic acid; thus, ATP decreases the conversion and Triton X-100 increases the conversion. Changes in the availability of photosynthetically generated reduced nicotinamide adenine dinucleotide phosphate apparently does not markedly affect the C16-C18 ratio. Various H2O2-generating systems, such as viologen dyes, inhibit oleate synthesis from acetate and cause stearate to accumulate. Catalase partially reverses the effect of these days. 2 Present address: Department of Botany, University of Newcastle upon Tyne, Newcastle upon Tyne NE 1 7RU, England. 1 Supported by National Institutes of Health Postdoctoral Fellowship GM 13319 to Curtis V. Givan and National Science Foundation Grant NSF GB-19733X to P. K. Stumpf. 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)