Plant Physiology

Upper, C. D.; Helgeson, John P.; Kemp, John D.; Schmidt, C. J.

doi: 10.1104/pp.45.5.543pmid: 16657339

Abstract Gas-liquid chromatographic retention times for 20 purines or purine nucleosides, 14 of which are highly active cytokinins, are reported. With one exception, all of the naturally occurring cytokinins are separated. Ethyl acetate extraction of yeast transfer RNA hydrolysates and of culture filtrates of Agrobacterium tumefaciens gave sufficient concentration of the naturally occurring cytokinins for immediate gas-liquid chromatography. This procedure permitted the detection of 6-(3-methyl-2-butenylamino)-9-β, d-ribofuranosylpurine in yeast transfer RNA extracts. An active cytokinin was isolated from A. tumefaciens culture filtrates and was tentatively identified as 6-(3-methyl-2-butenylamino)purine. This content is only available as a PDF. © 1970 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)

Powell, Robert D.; Morgan, Page W.

doi: 10.1104/pp.45.5.548pmid: 16657340

Abstract Conditions influencing the opening of the bean (Phaseolus vulgaris L.) and cotton (Gossypium hirsutum L.) hypocotyl hook were defined. Such hooks were shown to undergo geotropic curvature; orientation of the hook with respect to gravity greatly affected the observed opening. Cotton and bean hooks behaved exactly opposite in regard to the presence of the cotyledons and apical bud. The cotton hook required the cotyledons for opening, but the corresponding tissue slowed or inhibited opening of the bean hook. With cotton, lower hypocotyl and root tissues stimulated hook opening, but with bean, the tissues below the hook section had little effect. Kinetin and gibberellic acid both modified hook opening in light and dark; the former was inhibitory and the latter was stimulatory. Indoleacetic acid, at concentrations above 10−5 M, caused pronounced hook closing in red light but not in the dark. These effects were generally the same with both plants. In opening of the cotton hook, the cotyledons were not necessary as a light receptor tissue. None of the growth substances tested were able to substitute completely for the cotton cotyledon. Coumarin was a pronounced inhibitor of opening of the cotton hook, and this response was expressed to such a degree as to cause hook closure with bean tissue. Reduced oxygen levels inhibited hook opening in bean. Oxygen was required in processes subsequent to the light reaction, but not for the photochemical process. 1 This investigation was supported in part by the Cotton Producers Institute and the National Cotton Council of America; it is a contribution of the Texas Agricultural Experiment Station. A preliminary report of the work has been presented (Plant Physiol. Supplement 43: S-45. 1968.). This content is only available as a PDF. © 1970 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)

Morgan, Page W.; Powell, Robert D.

doi: 10.1104/pp.45.5.553pmid: 16657341

Abstract Coumarin, at concentrations between 1.0 and 0.1 mm, inhibited red light-induced opening of the etiolated bean hypocotyl hook. In addition, anthocyanin synthesis and geotropic bending were inhibited. Coumarin stimulated ethylene synthesis, and ethylene was shown to mediate the inhibitory actions of coumarin. This conclusion was supported by: (a) the parallel concentration dependence and time sequence of hook closing and ethylene synthesis, (b) the restriction of the bulk of coumarin-induced ethylene production to the curved portion of the hook where opening is expressed, (c) the ability of both coumarin and ethylene to reclose partially opened hooks, and (d) the ability of exogenous ethylene, in the amounts produced by coumarintreated hooks, to duplicate the inhibitory effects of coumarin. There was an increasing stimulation of growth of the straight portion of the hypocotyl hook section as coumarin concentrations were increased from 0.1 to 1.0 mm. This action of coumarin was not duplicated by ethylene and occurred regardless of the presence or absence of added ethylene. The results of this study suggest that many actions of coumarin in growth systems are mediated by ethylene produced in response to the coumarin. 1 A contribution of the Texas Agricultural Experiment Station. Research supported in part by Grant GB-5640, National Science Foundation. A preliminary report of this study appeared in Plant Physiol. 43: S-45. 1968. This content is only available as a PDF. © 1970 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)

Lane, T. R.; Stiller, Mary

doi: 10.1104/pp.45.5.558pmid: 5429350

Abstract The decarboxylation of endogenous free glutamic acid by Chlorella pyrenoidosa, Marburg strain, was induced by a variety of metabolic poisons, by anaerobic conditions, and by freezing and thawing the cells. The rate of decarboxylation was proportional to the concentration of inhibitor present. Possible mechanisms which relate the effects of the various conditions on glutamate decarboxylation and oxygen consumption by Chlorella are discussed. 3 Present address: The C. V. Mosby Co., 3207 Washington Blvd., St. Louis, Missouri 63103. 1 Supported by United States Public Health Service Grant GM 08037-04 to M. Stiller, and by a Predoctoral Fellowship from the National Institutes of Health to T. R. Lane. 2 Part of a dissertation submitted (by T. R. L.) to Purdue University in partial fulfillment of the requirements for the degree of Doctor of Philosophy. This content is only available as a PDF. © 1970 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)

Mantai, Kenneth E.

doi: 10.1104/pp.45.5.563pmid: 16657342

Abstract Digestion of spinach chloroplasts with pancreatic lipase or trypsin effectively uncoupled electron transport. Continued digestion led to inhibition of saturated rates of Hill reaction activity and a decrease in quantum yield. Irradiation with ultraviolet light decreased the quantum yield and inhibited Hill activity, but did not uncouple. Ascorbate-dichlorophenol-indophenol-mediated reduction of nicotinamide adenine dinucleotide phosphate was not appreciably inhibited by treatment with either of the enzymes or by ultraviolet irradiation. Carbonylcyanide m-chlorophenylhydrazone became a potent inhibitor of electron transport after trypsin treatment of chloroplasts. It also inhibited, rather than uncoupled, electron transport in glutaraldehyde-fixed chloroplasts. No other uncouplers tested showed these effects. Glutaraldehyde fixation of chloroplasts also greatly reduced the inhibitory effects of lipase and trypsin digestion but not the inhibition by ultraviolet irradiation. The inhibitory effects of trypsin and pancreatic lipase, and probably ultraviolet irradiation as well, appear to be due to a general breakdown of the membrane structure rather than inactivation of specific sites in the electron transport chain. 2 Present address: Department of Biology, Brookhaven National Laboratory, Upton, New York 11973. 1 Carnegie Institution of Washington Department of Plant Biology Publication 452. This content is only available as a PDF. © 1970 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)

Hopkins, D. W.; Butler, W. L.

doi: 10.1104/pp.45.5.567pmid: 16657343

Abstract Phytochrome was examined by immunochemical and spectroscopic techniques to detect differences between the protein moieties of red- and far red-absorbing phytochrome (P r and P fr). No differences in the reaction of P r and P fr with phytochrome antibody were discernible on Ouchterlony double diffusion plates. However, the microcomplement fixation assay showed a greater degree of antibody reaction with P fr than with P r, indicating some difference in the surface characteristics of the two forms. Circular dichroism spectroscopy between 300 and 200 nanometers revealed differences between P r and P fr which may reflect differences in the protein conformation. The circular dichroism spectrum of P r showed a negative band at 285 nanometers which was not present in the spectrum of P fr, and the large negative circular dichroism band at 222 nanometers with P fr, associated with the α-helical content, was shifted 2 nanometers to shorter wave length with P r although there was no change of magnitude of this band. The absorbancy of P r and P fr is very nearly the same in the 280 nanometer spectral region, but sensitive difference spectra between P r and P fr did reveal spectra which were similar to solvent perturbation spectra obtained by others with different proteins. In total, the experiments indicate that there are conformational differences between the protein moieties of P r and P fr but that these differences are rather slight from a standpoint of gross structure. This content is only available as a PDF. © 1970 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)

Smith, Richard C.

doi: 10.1104/pp.45.5.571pmid: 16657344

Abstract Xylem exudates were collected at hourly intervals from short segments which had been excised from two portions of the primary root of corn (Zea mays L.) seedlings and partially immersed in experimental salt solution containing 86Rb. All segments showed variation in rates of output of both volume and ions for several hours, after which a steady state was attained which persisted for many hours. Apical segments produced little or no exudate for several hours and did not reach a steady state until 18 or more hours after excision. Basal segments produced exudate containing detectable quantities of isotope within an hour and they reached a steady state about 12 hours after excision. During their respective steady states, apical segments produced three times the volume per hour and translocated eight times as much Rb per hour as did basal segments. These differences in the time course of exudation and the large differences in output are interpreted as indicating that two independent systems of ion transport operate simultaneously in intact roots. If this interpretation is correct, then it would appear that one of these systems has a greater potential capacity for ion transport than the other. 1 This work has been supported by Atomic Energy Commission Contract AT-(40-1)-3545. This content is only available as a PDF. © 1970 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)

Ingersoll, R. B.; Smith, O. E.

doi: 10.1104/pp.45.5.576pmid: 16657345

Abstract The movement of abscisic acid in the cotton explant was investigated by bioassay and radioisotope techniques. The rate of movement was 20 to 30 millimeters per hour with most of the abscisic acid moving unchanged through the explant into the basal agar. The rate of movement was the same through the abscission zone as through petiole tissue. Patterns of accumulation and metabolic products are discussed. This content is only available as a PDF. © 1970 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)

Obendorf, R. L.; Huffaker, R. C.

doi: 10.1104/pp.45.5.579pmid: 16657346

Abstract Activities of phosphoriboisomerase, phosphoribulokinase, and ribulose 1,5-diphosphate carboxylase, protein content, and chlorophyll accumulation in dark-grown barley seedlings were measured before and after illumination. Enzymatic activities, levels of soluble protein, and accumulation (upon illumination) of chlorophyll in leaves declined from tips toward the base. In response to increasing time of illumination, chlorophyll accumulation and activities of phosphoribulokinase and ribulose 1,5-diphosphate carboxylase (enzymes located in chloroplasts) increased most in tip portions whereas activity of phosphoriboisomerase and levels of soluble protein (constituents not confined to chloroplasts) increased similarly in all sections of the leaf. Maximum activity of phosphoribulokinase and maximum accumulation of chlorophyll shifted toward median portions of the leaf blade with increased age of seedling before illumination. Maximum activity of ribulose 1,5-diphosphate carboxylase and maximum level of soluble protein occurred in all leaf sections when the seedlings were 7 days of age before illumination. 1 Present address: Department of Agronomy, Cornell University, Ithaca, New York 14850. This content is only available as a PDF. © 1970 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)

Samaddar, K. R.; Scheffer, R. P.

doi: 10.1104/pp.45.5.586pmid: 16657348

Abstract Oat seeds of cultivars susceptible and resistant to Helminthosporium victoriae were held for various times in pathogen-produced, host-specific toxin solutions; control seeds were in water. Seeds were then washed thoroughly and incubated on moist paper, or dried and stored for 2-3 weeks before germination was attempted. In both cases, germination of susceptible seeds was prevented by previous exposure to toxin for 1 hour or more. Control seeds and treated resistant seeds grew normally. Toxin did not affect O2 uptake or loss of carbohydrates from seeds for the first 12 hours of imbibition. After 12 hours, toxin-treated susceptible seeds had higher respiration and lost more carbohydrates than did control seeds. Experiments with embryoless seeds showed that toxin blocked synthesis and secretion of α-amylase by susceptible but not by resistant aleurone cells. Resting aleurone cells were exposed briefly to toxin, then dried and stored until all toxin was gone. Susceptible aleurone cells treated in this way failed to produce α-amylase following exposure to gibberellic acid, while controls and resistant treated aleurone tissues produced amylase. Susceptibility or resistance to toxin appears to be expressed in resting and metabolically active tissues. 1 Journal Article 4917, Michigan Agricultural Experiment Station. Aided by National Science Foundation Grant GB-6560. This content is only available as a PDF. © 1970 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)