Plant Physiology

Green, Paul B.

doi: 10.1104/pp.43.8.1169pmid: 16656901

Abstract The view that the plant cell grows by the yielding of the cell wall to turgor pressure can be expressed in the equation: rate = cell extensibility × turgor. All growth rate responses can in principle be resolved into changes in the 2 latter variables. Extensibility will relate primarily to the yielding properties of the cell wall, turgor primarily to solute uptake or production. Use of this simple relationship in vivo requires that at least 2 of the 3 variables be measured in a growing cell. Extensibility is not amenable to direct measurement. Data on rate and turgor for single Nitella cells can, however, be continuously gathered to permit calculation of extensibility (rate/turgor). Rate is accurately obtained from measurements on time-lapse film. Turgor is estimated in the same cell, to within 0.1 atm or less, by measurement of the ability of the cell to compress gas trapped in the closed end of a capillary the open end of which is in the cell vacuole. The method is independent of osmotic equilibrium. It operates continuously for several days, over a several fold increase in cell length, and has response time of less than one minute. Rapid changes in turgor brought on by changes in tonicity of the medium, show that extensibility, as defined above, is not constant but has a value of zero unless the cell has about 80% of normal turgor. Because elastic changes are small, extensibility relates to growth. Over long periods of treatment in a variety of osmotica the threshold value for extensibility and growth is seen to fall to lower values to permit resumption of growth at reduced turgor. A brief period of rapid growth (5× normal) follows the return to normal turgor. All variables then become normal and the cycle can be repeated. The cell remains essentially at osmotic equilibrium, even while growing at 5× the normal rate. The method has potential for detailed in vivo analyses of “wall softening.” 1 Supported by National Science Foundation Grants GB 2575 and 6055X. This content is only available as a PDF. © 1968 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)

Hardy, R. W. F.; Holsten, R. D.; Jackson, E. K.; Burns, R. C.

doi: 10.1104/pp.43.8.1185pmid: 16656902

Abstract The methodology, characteristics and application of the sensitive C2H2-C2H4 assay for N2 fixation by nitrogenase preparations and bacterial cultures in the laboratory and by legumes and free-living bacteria in situ is presented in this comprehensive report. This assay is based on the N2ase-catalyzed reduction of C2H2 to C2H4, gas chromatographic isolation of C2H2 and C2H4, and quantitative measurement with a H2-flame analyzer. As little as 1 μμmole C2H4 can be detected, providing a sensitivity 103-fold greater than is possible with 15N analysis. A simple, rapid and effective procedure utilizing syringe-type assay chambers is described for the analysis of C2H2-reducing activity in the field. Applications to field samples included an evaluation of N2 fixation by commercially grown soybeans based on over 2000 analyses made during the course of the growing season. Assay values reflected the degree of nodulation of soybean plants and indicated a calculated seasonal N2 fixation rate of 30 to 33 kg N2 fixed per acre, in good agreement with literature estimates based on Kjeldahl analyses. The assay was successfully applied to measurements of N2 fixation by other symbionts and by free living soil microorganisms, and was also used to assess the effects of light and temperature on the N2 fixing activity of soybeans. The validity of measuring N2 fixation in terms of C2H2 reduction was established through extensive comparisons of these activities using defined systems, including purified N2ase preparations and pure cultures of N2-fixing bacteria. With this assay it now becomes possible and practicable to conduct comprehensive surveys of N2 fixation, to make detailed comparisons among different N2-fixing symbionts, and to rapidly evaluate the effects of cultural practices and environmental factors on N2 fixation. The knowledge obtained through extensive application of this assay should provide the basis for efforts leading to the maximum agricultural exploitation of the N2 fixation reaction. 1 Contribution No. 1451. This content is only available as a PDF. © 1968 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)

Suge, Hiroshi; Rappaport, Lawrence

doi: 10.1104/pp.43.8.1208pmid: 16656903

Abstract The relationship among gibberellins, CCC, vernalization, and photoperiod in the flowering response of radish, Raphanus sativus L., cv. Miyashige-sofuto, was studied. The optimal condition for flowering was vernalization and a 16-hour photoperiod; GA3 had no additional effect. Gibberellin A3 (60 μg total) was not able to induce flowering in nonvernalized plants grown on 8-hour days, but it did increase the percentage of nonvernalized plants that flowered under long days from 60 to 100. Gibberellin content of vernalized seedlings increased within the first 24 hours after seedlings were transferred to the greenhouse. Content reached a peak in the first 4 days after transfer and thereafter remained constant. Essentially no gibberellin was found in 2 day-old non-vernalized (control) seedlings of comparable size to the vernalized ones. Gibberellin content in the controls reached a peak on the fourth day of growth in the greenhouse; thereafter, it decreased steadily. Bolting was inhibited slightly by CCC when applied during vernalization; it was almost completely inhibited when CCC was applied after seed vernalization. Extraction experiments revealed that CCC actually reduced the gibberellin content when applied during or after vernalization. The dwarfing agent, however, had essentially no effect on flowering. We concluded that gibberellins likely play a direct role in bolting of `Miyashige-sofuto' radish, but probably are not directly functional in initiating flowering. 1 On leave from National Institute of Agricultural Sciences, Kita-ku, Tokyo, Japan. This content is only available as a PDF. © 1968 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, Jack C.

doi: 10.1104/pp.43.8.1215pmid: 16656904

Abstract Shortly after Zea mays L. plants were exposed to 14CO2, most of the radioactivity in the kernel occurred in the free monosaccharides, glucose and fructose. Later the proportion of 14C in sucrose increased and that in the monosaccharides declined. These data have been interpreted as showing that the translocated sugar is hydrolyzed prior to or during its movement into the storage cells of the endosperm. This hydrolysis appears to occur in the “pedicel region” of the kernel. After entry into the endosperm tissue, sucrose was rapidly resynthesized from the monosaccharides prior to its utilization in starch synthesis. 1 Purdue Agricultural Experiment Station Journal Paper No. 3309. This content is only available as a PDF. © 1968 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)

Vold, Barbara S.; Sypherd, Paul S.

doi: 10.1104/pp.43.8.1221pmid: 5700016

Abstract Gross changes in protein and nucleic acid were studied in germinating wheat seeds. The nucleic acid fraction was separated on columns of methylated albumin-keiselguhr. It was found that more than 50% of the transfer RNA was lost from the embryo in the first 10 to 15 hours of germination. This was followed by a period of rapid resynthesis of transfer RNA, to the normal level at about 20 hours. The decline and increase in transfer RNA was accompanied by a change in the ratios of certain amino acid acceptor species. Evidence is also presented that an embryo ribonuclease is lost during the first 10 to 15 hours, followed by the appearance of a second seedling ribonuclease between 15 and 30 hours of germination. 1 Present address: Scripps Clinic and Research Foundation. La Jolla, California. This content is only available as a PDF. © 1968 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)

Ross, Cleon; Cole, C. V.

doi: 10.1104/pp.43.8.1227pmid: 16656905

Abstract The metabolism of cytidine-2-14C and uridine-2-14C was studied in discs cut from leaflets of bean plants (Phaseolus vulgaris L.). Cytidine was degraded to carbon dioxide and incorporated into RNA at about the same rates as was uridine. Both nucleosides were converted into the same soluble nucleotides, principally uridine diphosphate glucose, suggesting that cytidine was rapidly deaminated to uridine and then metabolized along the same pathways. However, cytidine was converted to cytidine diphosphate and cytidine triphosphate more effectively than was uridine. Cytidine also was converted into cytidylic acid of RNA much more extensively and into RNA uridylic acid less extensively than was uridine. Azaserine, an antagonist of reactions involving glutamine (including the conversion of uridine triphosphate to cytidine triphosphate), inhibited the conversion of cytidine into RNA uridylic acid with less effect on its incorporation into cytidylic acid. On the other hand, it inhibited the conversion of orotic acid into RNA cytidylic acid much more than into uridylic acid. The results suggest that cytidine is in part metabolized by direct conversion to uridine and in part by conversion to cytidine triphosphate through reactions not involving uridine nucleotides. 2 Research soil scientist, Agriculture Research Service, USDA. 1 Research supported by grant GB-4864 from the National Science Foundation. This content is only available as a PDF. © 1968 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)

Tang, Wen-Jing; Castelfranco, Paul A.

doi: 10.1104/pp.43.8.1232pmid: 16656906

Abstract The effect of activation (“aging”) of potato tuber slices on their phospholipid metabolism was investigated. Aged slices were incubated with 14C labeled choline, ethanolamine, methionine, serine, and acetate. In all cases, the incorporation of radioactivity into the lipid fraction increased with the length of time the slices were aged. This incorporation was shown to be true synthesis and not exchange between precursors and existing phospholipids. The increased incorporation of labeled choline into lipids was mainly due to an increase in its uptake by the tissue, the presence of actidione during aging prevented this increased uptake. The increase in the incorporation of labeled acetate into lipids resulted from the development of a fatty acid synthetase during aging. In the case of ethanolamine, both its uptake into the tissue and its incorporation into the lipid fraction increased. The phospholipids formed from these precursors were identified by paper and thin-layer chromatography. The major compound formed from choline was lecithin, while phosphatidylethanolamine and a small amount of lecithin were formed from ethanolamine. 1 Supported in part by research grant GM-07532 from the United States Public Health Service. This content is only available as a PDF. © 1968 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)

Briggs, Winslow R.; Zollinger, Wendell D.; Platz, Barbara B.

doi: 10.1104/pp.43.8.1239pmid: 16656907

Abstract Phytochrome was partially purified from etiolated seedlings of Avena sativa L. Several properties of the red-absorbing (PR) and far-red absorbing (PFR) forms of the pigment were compared. The 2 forms could not be shown to differ with respect to their sedimentation velocity in sucrose density gradients, elution volume from Sephadex G-200 columns, binding properties on calcium phosphate, or electrophoretic mobility. PFR, however, was more labile than PR during precipitation with 50% ammonium sulfate. Sephadex G-200 elution diagrams obtained with fresh phytochrome preparations revealed 2 components of different molecular weights, 1 roughly 180,000, and 1 roughly 80,000. Native phytochrome had an absorption spectrum in vivo showing an absorption maximum for PR of 667 nm. Both the large and small forms of phytochrome mentioned above can be maintained with an absorption maximum for PR of 667 nm. However, allowing them to remain for several hours as PFR, even at 4°, shifted this peak to 660 nm. The protein conformational change during phytochrome transformation may be quite small, though the various comparative techniques used do not strictly rule out a fairly large one. The need for maintaining the pigment as PR during all steps of purification, but particularly during ammonium sulfate precipitation is underscored. 2 Present address: The Biological Laboratories, Harvard University, Cambridge, Massachusetts 02138. 1 Supported 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. © 1968 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)

Kende, Hans; Tavares, James E.

doi: 10.1104/pp.43.8.1244pmid: 5700017

Abstract The clarification of the following 2 questions was attempted: (a) are cytokinins precursors in the formation of sRNA, (b) is the observed incorporation of cytokinins into sRNA related to the action of the hormone? Although Escherichia coli contains cytokinins in its sRNA, no cytokinin auxotroph mutants of E. coli could be found and the statistical probability for the existence of such mutants is extremely low. This suggests that cytokinins are not precursors in the synthesis of sRNA. A radioactive cytokinin, 6-benzylamino-9-methyl-purine was synthesized and it was tested whether or not it is incorporated into sRNA of soybean callus tissue. Masking the 9-position of the purine inhibited the incorporation of this cytokinin into RNA while not affecting its biological activity. This is taken as an indication that the observed incorporation of cytokinins such as benzyladenine into sRNA is not related to the action of this hormone. This content is only available as a PDF. © 1968 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)

Friedlander, Michael; Neumann, Joseph

doi: 10.1104/pp.43.8.1249pmid: 5700018

Abstract Serum albumin was shown to stimulate markedly various photoreactions in isolated bean and lettuce chloroplasts. The maximal effect was obtained when this compound was present during the homogenization step and continuously in the chloroplast preparation. The “basal” electron transport was enhanced using various acceptors and stimulation was obtained also in the presence of uncouplers. The quantum requirement for ferricyanide reduction was appreciably reduced. Serum albumin increased the rate of cyclic phosphorylation and the ratio of P/e2 in non-cyclic phosphorylation. The increase in phosphorylation is supposedly due to inhibition of the rate of decay of the high energy non-phosphorylated intermediate, XE. It is postulated that serum albumin affects chloroplast photoreactions by binding endogenously released unsaturated fatty acids. 1 This paper is a part of a M. S. Thesis to be submitted to Tel-Aviv University, Tel-Aviv. This content is only available as a PDF. © 1968 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)