Plant Physiology

Epstein, Ephraim; Cohen, Jerry D.; Bandurski, Robert S.

doi: 10.1104/pp.65.3.415pmid: 16661204

Abstract The amounts and rates of metabolic turnover of the indolylic compounds in germinating kernels of sweet corn were determined. Knowledge of pool size and rate of pool turnover has permitted: (a) identification of indole-3-acetyl-myo-inositol as the major chemical form for transport of indole-3-acetic acid (IAA) from endosperm to shoot; (b) demonstration that the free IAA of the endosperm is turning over rapidly with a half-life of 3.2 hours; (c) identification of esters of IAA as the immediate precursors of IAA in the endosperm and shoot; (d) demonstration that neither tryptophan nor tryptamine is a major precursor of IAA for the seed or shoot; (e) identification of IAA-myo-inositol glycosides as precursors of IAA-myo-inositol. It is concluded that seedlings of Zea mays utilize esters of IAA, and not tryptophan or its derivatives, for the IAA requirements of the germinating seedling. 2 Accomplished this research while on sabbatical leave from the Department of Horticulture, The Volcani Center, Bet Dagan, Israel. 3 To whom reprint requests should be addressed. 1 This work was supported by grants from the Metabolic Biology Section of the National Science Foundation, PCM 76-12356. Journal Article 8953 from the Michigan Agricultural Experiment Station. This content is only available as a PDF. © 1980 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)

Nowacki, Janusz; Bandurski, Robert S.

doi: 10.1104/pp.65.3.422pmid: 16661205

Abstract Indole-3-acetyl-myo-inositol esters constitute 30% of the low molecular weight derivatives of indole-3-acetic acid (IAA) in seeds of Zea mays. [14C]Indole-3-acetyl-myo-inositol was applied to a cut in the endosperm of the seed and found to be transported from endosperm to shoot at 400 times the rate of transport of free IAA. The rate of transport of indole-3-acetyl-myo-inositol from endosperm to shoot was 6.3 picomoles per shoot per hour and thus adequate to serve as the seed auxin precursor for the free IAA diffusing downward from the shoot tip. Indole-3-acetyl-myo-inositol is the first seed auxin precursor to be identified. Application of either [14C]IAA or 14C-indole-3-acetyl-myo-inositol ester to the endosperm results in both free and esterified [14C]IAA in the seedling shoot. Esterification of free IAA and hydrolysis of indole-3-acetyl-myo-inositol occurred in the shoot and not the endosperm yielding ratios of ester to free IAA which approximate the ratios of ester to free IAA normally found in corn shoot tissue. This proves, for the first time, that esterified IAA and free IAA are interconvertible in the growing shoot. Since free IAA may be limiting for plant growth, knowledge that the free hormone is in “equilibrium” with its conjugates suggests new methods for the control of plant growth. 2 Present address: Research Institute of Pomology 96-100 Skierniewice, Poland. 3 To whom reprint requests should be directed. 1 This work was supported by the Metabolic Biology Section of the National Science Foundation, PCM 76-12356. Journal Article 8954 from the Michigan Agricultural Experiment Station. This content is only available as a PDF. © 1980 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)

O'Toole, John C.; Cruz, Rolando T.

doi: 10.1104/pp.65.3.428pmid: 16661206

Abstract Numerous studies have associated increased stomatal resistance with response to water deficit in cereals. However, consideration of change in leaf form seems to have been neglected. The response of adaxial and abaxial stomatal resistance and leaf rolling in rice to decreasing leaf water potential was investigated. Two rice cultivars were subjected to control and water stress treatments in a deep (1-meter) aerobic soil. Concurrent measurements of leaf water potential, stomatal resistance, and degree of leaf rolling were made through a 29-day period after cessation of irrigation. Kinandang Patong, an upland adapted cultivar, maintained higher dawn and midday leaf water potential than IR28, a hybrid selected in irrigated conditions. This was not explained by differences in leaf diffusive resistance or leaf rolling, and is assumed to result from a difference in root system extent. Stomatal resistance increased more on the abaxial than the adaxial leaf surface in both cultivars. This was associated with a change in leaf form or rolling inward of the upper leaf surface. Both responses, increased stomatal resistance and leaf rolling, were initiated in a similar leaf water potential range (−8 to −12 bars). Leaves of IR28 became fully rolled at leaf water potential of about −22 bars; however, total leaf diffusive resistance was only about 4 to 5 seconds per centimeter (conductance 0.25 to 0.2 centimeter per second) at that stage. Leaf diffusive resistance and degree of leaf rolling were linearly related to leaf water potential. Thus, leaf rolling in rice may be used as an estimate of the other two less obvious effects of water deficit. This content is only available as a PDF. © 1980 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)

Woo, K. C.; Jokinen, Mark; Canvin, David T.

doi: 10.1104/pp.65.3.433pmid: 16661207

Abstract Substantial rates of nitrate reduction could be achieved with a reconstituted system from spinach leaves containing supernatant, mitochondria, NAD+, oxaloacetate (OAA), and an oxidizable substrate. Appropriate substrates were glycine, pyruvate, citrate, isocitrate, fumarate, or glutamate. The reduction of NO3− with any of the substrates could be inhibited by n-butyl malonate, showing that the transfer of reducing power from the mitochondria to the supernatant involved the malate exchange carrier. The addition of ADP to the reconstituted system decreased NO3− reduction and this decrease could be reversed by the addition of rotenone or antimycin A. The operation of the OAA/malate shuttle was achieved most quickly in the system when low concentrations (≤0.1 millimolar) of OAA were added. A corresponding increase in the lag time for the operation of the OAA/malate shuttle was observed when the OAA concentration was increased. Concentrations for half-maximal activity of OAA, glycine, NAD+, and NO3− in the reconstituted system were 42 micromolar, 0.5 millimolar, 0.25 millimolar, and 26 micromolar, respectively. The transfer of reducing power from the mitochondria to the soluble phase via the OAA/malate shuttle can not only provide NADH for cytoplasmic reduction but can also sustain oxidation of tricarboxylic cycle acids and the generation of α-ketoglutarate independently of the respiratory electron transport chain. 2 Present address: Department of Botany, University of Western Australia, Nedlands, Western Australia 6009. 1 This work was supported in part by the National Research Council of Canada. This content is only available as a PDF. © 1980 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)

Nishinari, Noriko; Syōno, Kunihiko

doi: 10.1104/pp.65.3.437pmid: 16661208

Abstract During the course of partially synchronized cell divisions in cultured tobacco (Xanthi) cells the amount of endogenous cytokinins in the butanol-soluble fraction increased 5 to 10 times in 3 hours and paralleled the increase in frequency of mitosis. Among three cytokinins detected in tobacco cells, the activity corresponding to the RF of authentic zeatin in thin layer chromatography changed in parallel with the mitotic index. 1 This work was supported by Grant 348010 from the Ministry of Education, Japan. This content is only available as a PDF. © 1980 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)

Hitz, William D.; Stewart, Cecil R.

doi: 10.1104/pp.65.3.442pmid: 16661209

Abstract The levels of ribulose 1,5-bisphosphate (RuBP), 3-phosphoglyceric acid (PGA), glycolate, glycine, and serine were measured in soybean leaflets during photosynthesis in atmospheres ranging from 1 to 60% O2 and from 0 to 500 microliters per liter CO2. The RuBP level remained constant as CO2 concentration was decreased in atmospheres containing 20 or 60% O2, but increased as CO2 concentration was decreased in atmospheres containing 1% O2. PGA levels decreased at CO2 concentrations near or below the CO2 compensation point under all O2 concentrations. The glycolate pool at 300 microliters per liter CO2 increased slightly with increasing O2 concentration, but remained nearly constant at very low CO2. The serine pool showed no measurable change over the range of CO2 or O2 concentrations tested. The glycine pool did not change significantly with varying CO2 concentration but increased linearly with increasing O2 concentration. Measured RuBP levels indicate an RuBP concentration less than the estimated concentration of RuBP carboxylase/oxygenase active sites. The constant RuBP pool size in 20% O2, however, indicates that RuBP level does not limit photosynthesis or photorespiration any more at 50 microliters per liter CO2 than at 450 microliters per liter. 1 Present address: MSU-DOE Plant Research Lab, Michigan State University, East Lansing, Michigan 48824. This content is only available as a PDF. © 1980 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)

Ernst, Manfred; Hartmann, Elmar

doi: 10.1104/pp.65.3.447pmid: 16661210

Abstract An acetylcholine hydrolyzing enzyme was prepared and purified (40 times) from dwarf bean hypocotyl hooks. The purity of the enzyme was proved by polyacrylamide gel electrophoresis. The molecular weight of the enzyme was determined to be 65,000 daltons. Enzyme activity was the highest at pH 8.0 and between 30 and 36 C. The enzyme had an apparent affinity constant (K m) for acetylcholine of 460/micromolar. The affinity for substrate analogs increased from butyrylthiocholine to propionylthiocholine to acetylthiocholine. The enzyme activity was inhibited by choline, neostigmine, physostigmine, manganese, and calcium. Magnesium had no influence on the enzyme activity. We conclude that the enzyme from dwarf beans is an acetylcholinesterase (EC 3.1.1.7). 1 This work was supported by a grant from the Deutsche Forschungsgemeinschaft. This content is only available as a PDF. © 1980 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)

Wang, Wei-Yeh

doi: 10.1104/pp.65.3.451pmid: 16661211

Abstract When seeds of Echinochloa crusgalli var. oryzicola are germinated in dark anaerobic conditions (99.995% N2), the seedlings do not have detectable protochlorophyll(ide). Two hours after exposure to light aerobic conditions, they begin to synthesize chlorophyll. The lag in greening is shorter in seedlings exposed to light for 24 hours before exposure to air. Seedlings maintained in light anaerobic conditions exhibit no lag in greening upon transfer to an aerobic environment. Preillumination of anaerobically grown seedlings does not result in any chlorophyll accumulation. Phytochrome is probably the receptor for photoactivation of chlorophyll synthesis, since activation is achieved by red light alone, but not by far red light or red plus far red light. The cytochrome oxidase activity in anaerobically germinated seedlings is 30% of the normal level found in aerobically grown seedlings. Preillumination was also found to activate the ability of anaerobically germinated seedlings to increase their cytochrome oxidase activity upon exposure to air. This content is only available as a PDF. © 1980 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)

Ackerson, Robert C.

doi: 10.1104/pp.65.3.455pmid: 16661212

Abstract The threshold leaf water potential required to initiate stomatal closure in cotton (Stoneville 213) became progressively more negative when plants were subjected to a series of water stress cycles. The shift in the threshold water potential required for induction of stomatal closure was dependent on the number of previous stress cycles and leaf age. The basal level of endogenous abscisic acid (ABA) in fully turgid leaves increased in response to the stress treatments, whereas the amount accumulated in response to a subsequent stress did not differ greatly among plants that had experienced different degrees of stress conditioning. Stomatal sensitivity to (±)-ABA fed through the transpiration stream was enhanced in detached leaves of plants which had experienced repetitive water stresses. The increased sensitivity was apparently the result of ABA synthesized during the stress periods since foliar applications of ABA sensitized stomata in an analogous manner. Furthermore, the amount of (+)-ABA required to initiate stomatal closure in leaves from the various stress treatments was not related to the amounts accumulated during wilting. 1 Contribution No. 2661 from Central Research and Development Department, Experimental Station, E. I. du Pont de Nemours and Company, Wilmington, Delaware 19898. This content is only available as a PDF. © 1980 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)

James, Douglas W.; Elbein, Alan D.

doi: 10.1104/pp.65.3.460pmid: 16661213

Abstract The antibiotics Streptovirudin and 24010 were tested to determine their effects on the formation of lipid-linked saccharide intermediates associated with glycoprotein biosynthesis in mung bean (Vigna radiata) and suspension-cultured soybean cells (Glycine max cv. Mandarin). In vitro both compounds strongly inhibited the transfer of N-acetyl[3H]glucosamine from UDP-N-[3H]acetylglucosamine to N-acetylglucosaminyl-pyrophosphoryl-polyisoprenol and lipid-linked oligosaccharides, although they had no apparent effect on the incorporation of [14C]mannose from GDP-[14C]mannose into mannosyl-phosphoryl-dolichol with a small inhibition into lipid-linked oligosaccharides. In vivo, Streptovirudin and tunicamycin dramatically inhibited the incorporation of N-[14C]acetylglucosamine and [3H]mannose into Pronase-released material (glycoproteins), whereas there was no effect on [3H]leucine incorporation into Pronase-released material (protein). Because the action of Streptovirudin and antibiotic 24010 in plants and other systems is similar to that for tunicamycin, these antibiotics are believed to be closely related. The use of tunicamycin is discussed with respect to its importance in studying glycoprotein biosynthesis and function in animal and plant systems. 1 This investigation was supported by National Institutes of Health Grant AM 21800. This content is only available as a PDF. © 1980 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)