Plant Physiology

Jaworski, J. G.; Kuć, J.

doi: 10.1104/pp.53.3.331pmid: 16658701

Abstract The rate of incorporation of 14C from acetate-1-14C into fatty acids by carrot root discs, 18 hours after inoculation with Ceratocystis fimbriata, was 9-fold greater than that in freshly cut discs. The rate in discs treated with water or Ethrel was 3-fold greater. The rate of incorporation of 14C from glucose-U-13C into fatty acids was 3-fold greater 18 hours after any of the above treatments. The rate of 14C incorporation from malonate-2-14C into fatty acids 24 hours after inoculation with C. fimbriata or treatment with water was 25 and 60%, respectively, of that in freshly cut discs. Linoleic acid was the principal fatty acid in carrot root, but incorporation of 14C from acetate-1-14C into the acid was low until 18 hours after inoculation with C. fimbriata or treatment with Ethrel. Turnover rates of the fatty acids appeared low and were similar for all treatments. There was little or no incorporation of 14C from acetate or malonate into 3-methyl-6-methoxy-8-hydroxy-3,4-dihydroisocoumarin (6-methoxy mellein) in fresh carrot discs or in discs treated with water, but label was incorporated rapidly in discs inoculated with C. fimbriata or treated with Ethrel. The rate of incorporation of label from acetate into fatty acids was severalfold higher than into 6-methoxy mellein, but the rate of incorporation of label from malonate was approximately equal into fatty acids and 6-methoxy mellein 24 hours after inoculation. The rate of fatty acid synthesis does not appear directly related to the accumulation of 6-methoxy mellein. 1 Journal Paper 4815 of the Purdue Agricultural Experiment Station, West Lafayette, Ind. 47907. 2 Research supported in part by Grant GB 13994A No. 1 of the National Science Foundation and a National Defense Education Act fellowship. This content is only available as a PDF. © 1974 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)

Sweeney, Beatrice M.

doi: 10.1104/pp.53.3.337pmid: 16658702

Abstract A circadian rhythm in the intracellular level of K+ in Gonyaulax polyedra is reported. When axenic cultures of Gonyaulax in continuous light (60-75 fot candles) are exposed for 4 hours to 0.1 or 0.2% ethanol, the subsequent free-running rhythm in stimulated bioluminescence is phase-shifted, the amount and direction of the shift being dependent on the time in the circadian cycle when cells are treated. The phase-response curve for ethanol closely resembles that for light in similarly maintained cells. When valinomycin (0.1 or 0.2 μg ml−1) is present in addition to ethanol, the phase of the bioluminescence rhythm is returned to that of an untreated cell suspension. Valinomycin thus negates the effect of ethanol on phase. The intracellular K+ level immediately after treatment of a cell suspension for 4 hours with ethanol (0.1%) is about half that of untreated cells. If valinomycin (0.1 μg ml−1) is also present during the 4-hour treatment, the intracellular K+ is only slightly lower than in untreated cells. Increasing the external concentration of K+ or Na+ for 4 hours has no effect on the rhythm of stimulated bioluminescence. These results are interpreted as support for the hypothesis that the mechanism by which circadian oscillations are generated involves changes in membrane properties. 1 This research was supported in part by Grant GB 8418 from the National Science Foundation. This content is only available as a PDF. © 1974 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)

Manabe, Katsushi; Furuya, Masaki

doi: 10.1104/pp.53.3.343pmid: 16658703

Abstract When mitochondria isolated from etiolated pea (Pisum sativum cv. Alaska) epicotyls were exposed briefly to red light, their ability to reduce exogenous NADP was enhanced. The red light effect was reversed by far red light. Photoreversible absorbance changes between 730 nm and 800 nm were spectrophotometrically detected in the purified mitochondria and its membrane fraction. The dehydrogenase activity in the mitochondria was heat-labile and was dependent on the presence of magnesium ion and appropriate substrates such as glucose 6-phosphate, isocitrate, pyruvate, 6-phosphogluconate, and succinate. The photoreversible effect was seen only for a few minutes after the irradiation, and was cancelled by hypotonic treatment or addition of Triton X-100. A similar but lesser effect was observed in the pea microsome fraction, whereas no photoreversible response was seen with a supernatant fraction resulting from centrifugation at 105g for 30 minutes. This content is only available as a PDF. © 1974 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)

Radin, J. W.; Loomis, R. S.

doi: 10.1104/pp.53.3.348pmid: 16658704

Abstract Polar transport of kinetin-8-14C occurred in segments of petioles, hypocotyls, and roots of radish (Raphanus sativus L.). The polarity was basipetal in petioles and hypocotyls and acropetal in roots. In segments excised from seedlings with fully expanded cotyledons, indole-3-acetic acid was required for polarity to develop. In hypocotyl segments isolated at this stage, basipetal and acropetal movements were equal during the first 12 hours of auxin treatment after which time acropetal movement declined. Pretreatment with auxin eliminated this delay in the appearance of polarity. In hypocotyl segments excised from seedlings with expanding cotyledons, exogenous auxin was unnecessary for polarity. Potassium cyanide abolished polarity at both stages of growth by allowing increased acropetal movement. The rate of accumulation of kinetin in receiver blocks was greater than the in vivo increase in cytokinin content of developing radish roots. 1 Present address: United States Department of Agriculture, Agricultural Research Service, Western Cotton Research Laboratory, 4135 E. Broadway, Phoenix, Arizona 85040. This content is only available as a PDF. © 1974 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)

Lisansky, Stephen G.; Galston, Arthur W.

doi: 10.1104/pp.53.3.352pmid: 16658705

Abstract Photoreversible phytochrome disappears from etiolated tissue upon actinic irradiation. Such disappearance, of possible physiological importance, involves several processes, at least one of which is accelerated by metals in vivo. Purified phytochrome from oat (Avena sativa L. cv. Garry) coleoptiles is greatly stabilized in vitro by scrupulous removal of metal impurities via chelating agents. Such stabilized phytochrome decays rapidly upon the addition of about 10 μm Hg2+, Cd2+, Cu2+, and Zn2+, all of which probably act on sulfhydryl groups. Other tested metals and growth factors were much less active or inactive. The metals effective in promoting decay do not affect the Pfr → Pr reversion process. This supports other evidence indicating the possible physiological importance of phytochrome “decay.” 2 This contribution represents part of a thesis submitted in 1973 to the Graduate School of Yale University in partial fulfillment of the requirements for a Ph.D. degree. 3 Present address: Philip Lyle Memorial Research Laboratory, University of Reading, RG6 2BX, England. 1 This work was aided by a National Science Foundation grant to A.W.G. This content is only available as a PDF. © 1974 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)

Turner, Neil C.

doi: 10.1104/pp.53.3.360pmid: 16658706

Abstract Diurnal changes in the vertical profiles of irradiance incident upon the adaxial leaf surface (I), leaf resistance (r 1), leaf water potential (ψ), osmotic potential (π), and turgor potential (P) were followed concurrently in crops of maize (Zea mays L. cv. Pa602A), sorghum (Sorghum bicolor [L.] Moench cv. RS 610), and tobacco (Nicotiana tabacum L. cv. Havanna Seed 211) on several days in 1968 to 1970 when soil water potentials were low. The r 1, measured with a ventilated diffusion porometer, of the leaves in the upper canopy decreased temporarily after sunrise [∼0530 hours Eastern Standard Time] as I increased, but then r 1 increased again between 0700 and 0830 hr Eastern Standard Time as the ψ, measured with a pressure chamber, decreased rapidly from the values of −7, −4 and −6 bars at sunrise to minimal values of −18, −22 and −15 bars near midday in the maize, sorghum, and tobacco, respectively. The π, measured with a vapor pressure osmometer, also decreased after sunrise, but not to the same degree as the decrease in ψ, so that a P of zero was reached in some leaves between 0730 and 0800 hours. The lower (more negative) π of leaves in the upper canopy than those in the lower canopy gave the upper leaves a higher P at a given ψ than the lower leaves in all three species; leaves at intermediate heights had an intermediate P. This difference between leaves at the three heights in the canopy was maintained at all values of ψ. The r 1 remained unchanged over a wide range of P and then increased markedly at a P of 2 bars in maize, −1 bar in sorghum, and near zero P in tobacco: r 1 also remained constant until ψ decreased to −17, −20, and −13 bars in leaves at intermediate heights in maize, sorghum, and tobacco, respectively. In all three species r 1 of leaves in the upper canopy increased at more negative values of ψ than those at the base of the canopy, and in tobacco, leaves in the upper canopy wilted at more negative values of ψ than those in the lower canopy. This content is only available as a PDF. © 1974 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)

Jaworski, Alan; Key, Joe L.

doi: 10.1104/pp.53.3.366pmid: 16658707

Abstract Methods are described by which ribosomal DNA can be enriched in subcellular fractions of carrot and soybean. With both carrot and cucumber it was possible to obtain a distinct satellite DNA which contained the rDNA. Hybridization values greater than 0.49% were necessary before a satellite component was observed. Saturation hybridization values for soybean, carrot, and cucumber DNA were 0.2, 0.49, and 1.14%, respectively. These values were increased 1.6- and 2-fold in soybean and carrot, respectively, but enrichment was not obtained for cucumber. 1 This work was supported by United States Public Health Service Grant CA 11624 from the National Cancer Institute. This content is only available as a PDF. © 1974 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)

Ort, Donald R.; Izawa, Seikichi

doi: 10.1104/pp.53.3.370pmid: 16658708

Abstract The rate of Hill reaction can be measured accurately as O2 uptake (the Mehler reaction) if a rapidly autoxidizable electron acceptor (e.g., methylviologen) is used. However, when an artificial electron donor-ascorbate couple (or ascorbate alone) replaces the natural donor, water, the rate of O2 consumption is no longer a reliable measure of the electron flux, because superoxide radical reactions contribute to O2 uptake. Such radical reactions, however, can be suppressed by adding enough superoxide dismutase to the reaction mixture. Indeed in all of the photosystem I- and photosystem II-donor reactions tested (except with benzidine which was tested without ascorbate added), the O2 uptake was inhibited by 30 to 50% by the addition of superoxide dismutase. The rate of phosphorylation was totally unaffected by the enzyme. The reasessment of the phosphorylation efficiencies thus made by the use of superoxide dismutase led us to the following conclusions. The phosphorylation efficiency associated with the transfer of electrons from a donor to methlylviologen (than to O2) through both photosystems II and I is practically independent of the donor used—catechol, benzidine, p-aminophenol, dicyanohydroquinone, or water. The P/e2 ratio is 1.0 ± 0.1. Only ascorbate gives a slightly lower value (P/e2 = 0.9). (NH2OH-treated, non-water-splitting chloroplasts were used for reactions with these artificial donors.) The phosphorylation efficiency associated with DCMU-insensitive, photosystem I-mediated transfer of electrons from a donor to methylviologen (then to O2) is again largely independent of the donor used, such as diaminodurene, diaminotoluene, and reduced 2,6-dichlorphenol-indophenol. The P/e2 ratio is 0.6 ± 0.08. 1 This work was supported by Grant GB37959x from the National Science Foundation. The preceding paper of this series, entitled “Studies on the energy coupling sites of photophosphorylation. IV. The relation of proton fluxes to the electron transport and ATP formation associated with Photosystem II,” by J. M. Gould and S. Izawa has been submitted to Biochim. Biophys. Acta for publication. This content is only available as a PDF. © 1974 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)

Mory, Y. Y.; Chen, D.; Sarid, S.

doi: 10.1104/pp.53.3.377pmid: 16658709

Abstract A soluble DNA-dependent DNA polymerase was extracted from wheat embryos. In vitro, the incorporation of radioactive thymidine triphosphate into acid-insoluble material is dependent upon the presence of the enzyme, all four deoxyribonucleotide triphosphates, Mg2+, and a DNA template. Incorporation occurs on native, alkali-denatured, and strictly double-stranded DNA. The in vitro synthesized product is a polydeoxynucleotide with a chain length shorter than the template; it has the same buoyant density as wheat embryo DNA when this DNA is used as template; and it forms a double-stranded complex with the DNA template. These data suggest that the in vitro DNA synthesis catalyzed by proteins extracted from wheat embryos occurs in a semiconservative way. This content is only available as a PDF. © 1974 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)