Plant Physiology

Zimmerman, D. C.; Vick, B. A.; Borg, T. K.

doi: 10.1104/pp.53.1.1pmid: 16658635

Abstract Differential centrifugation of several plant extracts indicates that the majority of the hydroperoxide isomerase activity is present in the cytoplasm of the cell. However, lesser amounts of isomerase activity were found in the mitochondrial and microsomal fractions of sunflower seedlings. Sucrose density gradient centrifugation of extracts from sunflower, watermelon, and flax seedlings and from cauliflower buds showed that isomerase activity was associated with the mitochondria. There was no evidence for presence of hydroperoxide isomerase activity in the microbodies. 1 Research Chemist, Agricultural Research Service, United States Department of Agriculture, in cooperation with the North Dakota Agricultural Experiment Station. Journal Article 437. 2 Graduate Fellowship, supported by National Defense Education Act IV. 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)

Ecklund, Paul R.; Moore, Thomas C.

doi: 10.1104/pp.53.1.5pmid: 16658651

Abstract Biosynthesis of the gibberellin precursor ent-kaurene-14C from mevalonic acid-2-14C was assayed in cell-free extracts of shoot tips of etiolated and light-grown Alaska (normal) and Progress No. 9 (dwarf) peas (Pisum sativum L.). During ontogeny of light-grown Alaska peas, kaurene-synthesizing activity increased from an undectectable level in 3-day-old epicotyls to a maximum in shoot tips of 9-day-old plants and remained relatively constant thereafter until postanthesis. The capacity for kaurene synthesis in extracts from shoot tips of 10-day-old etiolated Alaska seedlings increased approximately exponentially during the first 12 hr of de-etiolation in continuous high intensity white light and remained relatively constant during the succeeding 24 hr of irradiation. Extracts from light-grown Alaska (normal) shoot tips possessed greater capacity for kaurene synthesis than did extracts from light-grown Progress No. 9 (dwarf) shoot tips. Extracts from shoot tips of either light-grown cultivar displayed greater kaurene-synthesizing capacity than was observed in extracts from their dark-grown counterparts. It is concluded that gibberellin biosynthesis in pea shoot tips is subject to partial regulation by factors controlling the rate of biosynthesis of kaurene. 2 On leave from the Department of Biology, Vassar College, Poughkeepsie, N. Y. 12601; author and address for reprint requests. 1 Supported in part by a Grant-in-Aid of Faculty Research from Vassar College, Poughkeepsie, N. Y. to P. R. E. and in part by Grant GB-18494 from the National Science Foundation to T.C.M. 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)

Koller, H. R.; Thorne, J. H.

doi: 10.1104/pp.53.1.11pmid: 16658637

Abstract An apparatus to produce continuous gas mixtures for use in measurements of plant gas exchange is described. A wide range of CO2 and water vapor concentrations can be provided and O2 concentration can be varied from 0 to 21%. Changes in the concentrations of the components are accomplished conveniently, rapidly, and independently. With occasional adjustments, CO2 and O2 concentrations can be maintained to within ± 1 μl/l and ± 0.1%, respectively. Dew point of the gas mixture can be maintained to within ± 0.05 C. 1 Contribution from the Purdue University Agricultural Experiment Station, Lafayette, Ind. 47907. Journal Paper No. 5025. Research was supported in part by a grant from the Crop Improvement Council, National Soybean Processors Association. 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)

Haass, D.; Tanner, W.

doi: 10.1104/pp.53.1.14pmid: 16658644

Abstract Of nine species of unicellular algae tested, Chlorella vulgaris showed the highest inducibility for an active hexose transport system. Whereas the rate of uptake in all other species was increased by induction less than 5-fold, it was increased more than 400-fold in one strain of C. vulgaris. With glucose as inducer, the minimum time necessary to synthesize inducible proteins of the transport system was 15 minutes. The Km for induction with glucose is 5 μm and with 6-deoxyglucose 1 mm. The inducing sugars have to penetrate the cells to be effective. Evidence indicating that regulation of induction occurs at the transcriptional level was obtained. The induction was inhibited by 6-methylpurine. When cells were exposed to induce in the presence of actidione no increase in transport activity could be measured. After removal of actidione as well as the inducer, an increased uptake activity was observed after 30 to 60 minutes. The induced uptake system showed a turnover with a half-life of 4 to 6 hours at 26 C under nongrowing conditions; at 0 C turnover was negligible. Turnover was partly inhibited by anaerobic condition and by actidione; it was accelerated under growing conditions. 1 This work was supported by Deutsche Forschungsgemeinschaft. 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)

Chopowick, R. E.; Forward, D. F.

doi: 10.1104/pp.53.1.21pmid: 16658645

Abstract 14C-(UL)-l-Alanine was applied to the surface of mature leaves at the second node of sunflower (Helianthus annuus L. cv Commander) plants, under illumination. The alanine was absorbed during a 4-hour period, and some of it was metabolized by the absorbing tissue. After a lag period of about 15 minutes from first application, distribution of 14C through the plant proceeded in much the same pattern as when 14CO2 is assimilated by similar leaves. Most, if not all, of the 14C exported from the absorbing regions was in sucrose. Only minute amounts appeared in alanine or other amino acids in surrounding parts of the leaf blade or in the petiole, although these were strongly labeled in the tissue absorbing 14C-alanine. When 14CO2 was supplied for 15 minutes to leaves of different ages, amino acids were lightly labeled in the leaf blade. Mature green leaves exported only sucrose. Yellowing leaves on 60-day-old plants exported a variety of substances including amino acids. 2 Present address: Seneca College, 1750 Finch Ave. E., Willowdale, Ontario, Canada. 1 This work was supported in part by the National Research Council of Canada. 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)

Travis, R. L.; Key, Joe L.; Ross, Cleon W.

doi: 10.1104/pp.53.1.28pmid: 16658646

Abstract The in vitro protein synthetic activity of 80S ribosomes from leaves of dark-grown corn seedlings was enhanced (at low Mg2+ levels) by a 5-minute red light treatment applied 2 hours prior to tissue harvest. The effect was completely reversed by an immediate brief far red treatment, suggesting that ribosome activation is controlled by the phytochrome system. Experiments in which the interval between light treatment and tissue harvest was shortened indicate that the response was quite rapid. The initial increase in activity was detected within 30 minutes, followed by a rapid increase during the next 1.5 hours. No further increase occurred after 2 to 3 hours. The change in ribosome activity relates, at least in part, to an increase in the level of peptidyl-tRNA associated with ribosomes. Removal of peptidyl-tRNA from light-treated ribosomes also completely reversed the red light effect. Activation of ribosomes by 2 to 3 hours continuous white light (as previously reported) differs from red light activation in that reversal of this response requires salt washing of the ribosomes in addition to removal of peptidyl-tRNA. 2 Present address: Department of Botany and Plant Pathology, Colorado State University, Ft. Collins, Colo. 80521. 1 This research was supported by Atomic Energy Commission Contract AT (38-1)-643 to J.L.K. 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)

Coulson, Christopher; Heath, Robert L.

doi: 10.1104/pp.53.1.32pmid: 16658647

Abstract Isolated spinach chloroplasts have been used as a model system for studying the interaction of ozone, a component of photochemical smog, with plant membranes. Ozone bubbled into a suspension of isolated chloroplasts inhibits electron transport in both photosystems without uncoupling ATP production. Photosystem I (reduced 2,6-dichlorophenolindolphenol → NADP+) is a little more sensitive than photosystem II (H2O → 2,6-dichlophenolindolphenol). Ozone does not act as an energy transfer inhibitor, since the drop in ATP production and high energy intermediate (measured by amine-induced swelling) is nearly parallel to the decline in electron transport. A reasonable hypothesis is that ozone disrupts the normal pathway of energy flow from light-excited chlorophyll into the photoacts by a disruption of the components of the membrane but not a general disintegration of the membrane. In addition, ozone does not seem to penetrate into the grana region through the outer membrane of intact plastids, since ozone lowers the bicarbonate-supported O2 evolution but does not affect the rate of ferricyanide reduction in the same plastids after osmotic disruption. This would indicate that the effect of ozone on green plants, at low concentrations, may be due to the interaction of ozone with the first membrane it contacts and not directly with internal metabolic processes. 2 Present address: Department of Botany, University of Hull, Hull, Yorkshire, England. 1 This work was supported in part by United States Environmental Protection Agency Grant R801311. 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)

Bahr, James T.; Jensen, Richard G.

doi: 10.1104/pp.53.1.39pmid: 16658648

Abstract The properties of a form of ribulose diphosphate carboxylase having a high affinity for CO2 have been studied. Its apparent Km(HCO3−) of 0.5 to 0.8 mm (pH 7.8) and calculated Km(CO2) of 11 to 18 μm are comparable to the values exhibited by intact chloroplasts during photosynthesis. This form of the enzyme was released from chloroplasts in hypotonic media and was unstable, rapidly converting to a form having a high Km(HCO3−) of 20 to 25 mm similar to that for the purified enzyme. Incubation of the enzyme with MgCl2 and HCO3− yielded a third form with an intermediate Km(HCO3−) of 2.5 to 3.0 mm. The low Km form had sufficient activity both at air levels of CO2 and at saturating CO2 to account for the rates of photosynthesis by intact chloroplasts. The low Km form could be stabilized in the presence of ribose 5-phosphate, adenosine triphosphate, and MgCl2, at low temperatures for up to 2 hours. 1 This research was supported by Grant GB-27453 from the National Science Foundation to R.G.J. 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)

Adato, I.; Gazit, S.

doi: 10.1104/pp.53.1.45pmid: 16658649

Abstract Differential rates of water loss were achieved in picked avocado (Persea americana Mill.) fruits, either by controlling the evaporation rate or by supplying water through the fruit stalk. A negative linear correlation was found between the daily rate of water loss from fruits and their ripening, as determined by the time from harvest to peak of ethylene production. Ripening rate was hastened by 40% in fruits which had lost water at rate of 2.9% fresh weight per day, compared with those which lost only 0.5% per day. 1 Contribution from the Agricultural Research Organization, Volcani Center, Bet Dagan, Israel. 1973 Series, No. 131E. 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)

Fiscus, Edwin L.

doi: 10.1104/pp.53.1.47pmid: 16658650

Abstract An automatic digital diffusion porometer circuit is described. The circuit is highly stable with respect to temperature and supply voltage. The device is capable of high timing accuracy over very short measurement intervals, so that measurements may be made rapidly without the danger of stomatal changes occurring during the measurement period. 1 This work was supported by National Science Foundation Grant GB-30367X. 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)