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At least 325 records · Page 18Linked to original sources
PubMed1972

Regulation of cell division and cell enlargement by turgor pressure.

Isolated radish (Raphanus sativus L., var. Red Prince) cotyledons were incubated in growth medium plus graded concentrations of mannitol (-1 to -16 bars) for 28 hours. At the end of the incubation period, turgor pressures were measured using thermocouple psychrometers. Cell division, as measured by DNA increase, was greatly stimulated by increasing turgor from 5 to 6 bars. Cell enlargement was stimulated as turgor increased above 3 bars. The critical turgor pressure for increased cell division thus appeared significantly greater than that for increased cell enlargement.

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PubMed1974

Polar transport of kinetin in tissues of radish.

Polar transport of kinetin-8-(14)C 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.

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PubMed1974

Dose-response curves for radish seedling phototropism.

Radish seedlings (Raphanus sativus L.) were grown for 4 days in complete darkness, or in white light, or for 3 days in darkness followed by 1 day of red light. Phototropic dose-response curves for the seedlings grown in these three ways were determined with 460-nm light. The dark-grown and red light-treated seedlings responded with positive curvatures of no more than 10 degrees to energy doses in the first positive range and with larger positive curvatures in the second positive dose range. No indifferent or negative curvature was seen with the light intensity used. White light-grown seedlings did not respond to first positive energy doses, but responded as strongly to second positive doses as the other types of seedlings.

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PubMed1975

Promotion of radish cotyledon enlargement and reducing sugar content by zeatin and red light.

Effects of zeatin on amino acid and sugar contents of detached radish (Raphanus sativus L.) cotyledons were investigated to determine if accumulation of these solutes contributes to cytokinin-enhanced growth. Protein and amino acid levels were not significantly affected, but in cotyledons incubated in light the hormone caused greater accumulations of reducing sugars than occurred in light controls. Continuous fluorescent light or a few minutes of red light increased both the growth rate and the reducing sugar levels compared to dark controls. A far red treatment following red light overcame the promoting effect of the latter. Amounts of reducing sugars were closely associated with growth under the above conditions. Activity of an unidentified amylase was elevated by continuous light or a red light treatment (nullifiable by far red), suggesting that reducing sugars were derived from starch. Zeatin-treated cotyledons exhibited less amylase activity than did light controls, perhaps implicating cytokinin-stimulated conversion of fats to sugars in light. In darkness zeatin promoted cotyledon growth but did not increase sugar levels nor amylase activity, suggesting that enhanced ion accumulation also contributes to the more rapid water uptake leading to growth.

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PubMed1975

Development and intracellular distribution of enzymes of the oxidative pentose phosphate cycle in radish cotyledons.

Developmental and compartmentation studies were used to evaluate the relative roles of the oxidative pentose phosphate cycle, the Calvin cycle, and the glycolysis in cotyledons of radish (Raphanus sativus L.).Glucose-6-P dehydrogenase, 6-P-gluconate dehydrogenase, glucose-6-P isomerase, and the NAD-dependent glyceraldehyde-3-P dehydrogenase were present in high activity in ungerminated seeds, increased about 2-fold during germination in the dark, and were slightly enhanced by light. In contrast, NADP-dependent glyceraldehyde-3-P dehydrogenase was developed to only a small degree in the dark, but increased severalfold in continuous white or far red light. The activity of phosphofructokinase was low throughout germination.The separation of cell compartment-specific isoenzymes showed that, except in ungerminated seeds, the plastid enzyme accounted for 40 to 45% of the total activity of 6-P-gluconate dehydrogenase and for 15 to 20% of glucose-6-P isomerase. The remaining activity was due to the cytosolic isoenzymes. The presence of glucose-6-P dehydrogenase and 6-P-gluconate dehydrogenase in plastids was also established by their presence in the isolated organelle. The NAD-dependent glyceraldehyde-3-P dehydrogenase was mostly due to the cytosolic isoenzyme, whereas the NAD-dependent activity associated with the NADP-dependent glyceraldehyde-3-P dehydrogenase was very small.The data indicate that the enzymes of the oxidative pentose phosphate cycle are present in the cytosol throughout germination. In the plastids these enzymes already became fully developed during early germination in the dark, whereas enzymes of the Calvin cycle increased only in the light. Glycolysis seemed to be of minor importance.

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PubMed1976

Red Light-enhanced Phytochrome Pelletability: Re-examination and Further Characterization.

Red light-enhanced pelletability of phytochrome was observed in extracts of all 11 plants tested: Avena sativa L., Secale cereale L., Zea mays L., Cucurbita pepo L., Sinapis alba L., Pisum sativum L., Helianthus anuus L., Raphanus sativus L., Glycine max (L.) Merr., Phaseolus vulgaris L., and Lupinus albus L. This enhanced pelletability was observed in all 11 plants following in situ irradiation (in vivo binding) but only in Sinapis and Cucurbita after irradiation of crude extracts (in vitro binding). In vivo binding was not strongly dependent upon pH and, with few exceptions, was not markedly sensitive to high salt concentration, whereas in vitro binding was completely reversed by both high pH and high salt concentration. However, both binding phenomena were observed only with a divalent cation in the extract buffer. In vivo binding was further characterized using Avena which showed an increase in pelletability from less than 10% in dark control extracts to more than 60% in extracts of red light-irradiated shoots. The half-life for binding was 40 seconds at 0.5 C and was strongly temperature-dependent, binding being complete within 5 to 10 sec at 22 C. If pelletable phytochrome in the far red-absorbing form was photoconverted back to the red-absorbing form in situ, phytochrome was released from the pelletable condition with a half-life of 25 minutes at 25 C and 100 minutes at both 13 C and 3 C. No cooperativity in red light-enhanced pelletability with respect to phytochrome-far red-absorbing form was observed.

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PubMed1977

Formation of N-acetylglutamate by extracts of higher plants.

The enzymic synthesis of N-acetylglutamate was studied in extracts of higher plant tissues, especially in sugar beet leaves (Beta vulgaris L.). Sugar beet leaves had an enzyme that transferred the acetyl group either from acetyl-CoA or from N(2)-acetylornithine to glutamate. The enzyme was so unstable that special precautions were necessary for its detection and appreciable purification was impossible. The Km values were 2.5 and 0.025 mM for acetyl-CoA and N(2)-acetylornithine, respectively. The Km for glutamate was 23 mM with acetylornithine-glutamate transacetylase and 2.7 mM with acetyl-CoA-glutamate transacetylase. The pH optimum for acetyl-CoA-glutamate transacetylase was about 7.2 whereas that for acetylornithine-glutamate transacetylase was about 8.3. Acetylphosphate, N(2)-acetyl-2,4-diaminobutyrate, propionyl-CoA, and succinyl-CoA were not substrates.Arginine inhibited the acetyl-CoA-glutamate transacetylase and acetylglutamate phosphokinase but had no effect on the acetylornithineglutamate transacetylase. Related compounds had either no effect or much less than arginine. Arginine had no effect on enzyme levels.Acetyl-CoA-glutamate transacetylase was also found in Raphanus sativus L., Glycine max L. Merr., Arachis hypogaea L., Brassica rapa L., and Pisum sativum L. Acetylornithine-glutamate transacetylase was found in all of the above species plus Zea mays L., Avena sativa L., and Triticum aestivum L.

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PubMed1979

A Mechanism of Chlorosis Caused by 1,3-Dimethyl-4-(2,4-dichlorobenzoyl)-5-hydroxypyrazole, a Herbicidal Compound.

In organic solvents, 1,3-dimethyl-4-(2,4-dichlorobenzoyl)-5-hydroxypyrazole (DTP) converted chlorophyll a and b extracted from rice seedlings (Oryza sativa L. ;Kinmaze') into pheophytin a and b, respectively. On comparing the chlorophyll-converting activity of DTP to those of acetic, glycolic, 2,4-dichlorobenzoic, monochloroacetic, 2,6-dichlorobenzoic, pyruvic, and dichloroacetic acids, it was demonstrated that DTP induced H(+) into chlorophyll specifically. 5-Hydroxypyrazoles, which seem to be dissociable, converted chlorophyll into pheophytin in vitro. These compounds also induced chlorosis in sedge seedlings (Cyperus serotinus Rottb.), when the seedlings were grown in media containing these compounds. However, 5-hydroxypyrazoles, which seem to be undissociable, and analogs having no hydroxy group caused neither the chlorophyll conversion in vitro nor chlorosis in the seedlings. Chlorosis in barnyardgrass seedlings (Echinochloa crus-galli Beauv. var. oryzicola Ohwi) induced by DTP was reversed by cultivating the seedlings in media containing DTP plus NaOH, KOH, NH(4)OH, Ca(OH)(2), sodium acetate, sodium pyruvate, sodium succinate, or sodium fumarate. Accumulation of the vinyl pheoporphyrin fraction in 4- day-old etiolated radish cotyledons (Raphanus sativus L. ;Minowase 2') was enhanced by incubating the cotyledons with delta-aminolevulinic acid in the dark. However, simultaneous treatment with delta-aminolevulinic acid and DTP reduced accumulation of the fraction and promoted formation of the uro, copro, and protoporphyrin fractions. These results suggest that DTP blocks the synthesis of protochlorophyllide in intact plants and induces consequent chlorosis, and the H(+) -donating activity of DTP might cause the reduction of protochlorophyllide biosynthesis.

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PubMed1981

Distribution of Foliar-applied Boron Measured by Spark-source Mass Spectrometry and Laser-probe Mass Spectrography.

The distribution of foliar-applied boron ([(10)B]boric acid) in radish (Raphanus sativus L.) was studied using for analysis of the stable isotopes a technique allowing a high sensitivity: spark-source mass spectrometry. Boron was recovered in the nontreated aerial parts and in the roots; however, the greatest fraction was in the treated leaf. It was possible with a laser-probe mass spectrograph to show that boron was not superficially located in the treated area but was present in tissues at all levels of depth considered.

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PubMed1981

Cytokinin-induced wall extensibility in excised cotyledons of radish and cucumber.

The mechanism of cytokinin-induced cell expansion in cotyledons excised from dark-grown seedlings of radish (Raphanus sativus L.) and cucumber (Cucumus sativus L.) was studied. Cotyledons were incubated in dim light with or without 17 micromolar zeatin for periods up to 3 days. Fresh weights and osmotic potentials were measured daily. Cell wall extensibility properties were measured before and after the growth period. Also, experiments in which radish cotyledons were grown in mannitol solutions of various concentrations were performed. Comparisons of growth rates and increases of tissue osmotic potentials (toward zero) during growth without mannitol indicate that wall extensibility increased during the growth period and that this extensibility was enhanced by zeatin.Extensibility values derived from growth rates in mannitol provided indirect evidence of zeatin-increased wall extensibility. These conclusions were verified by direct measurements of plasticity with an Instron extensiometer. Thus, growth stimulation of excised cotyledons by cytokinins apparently involves wall loosening, in addition to previously demonstrated increases of K(+) absorption and formation of reducing sugars.

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PubMed1981

Effect of polar lipids on ATPase activity of membrane preparations from germinating radish seeds.

Membrane preparation (sedimenting between 13,000(g) and 80,000(g)) of germinating radish seeds (Raphanus sativus L.) was active in hydrolyzing ATP and, to a lesser extent, a variety of other phosphorylated compounds. Dicyclohexylcarbodiimide (DCCD) and diethylstilbestrol significantly inhibited the ATPase activity (40%) while their effect on hydrolysis of other phosphorylated compounds was much less.The sucrose density gradient analysis of the membrane preparation showed that the position of the DCCD-sensitive K(+)-dependent ATPase was similar to that found for plasma membrane of other plant material.Cholate treatment of membrane preparation removes almost all phospholipids, and ATPase activity is barely detectable. However, the addition of polar lipids completely restores the ATPase activity but does not restore general phosphatase activity.The ATPase of the polar lipids restored cholate preparation, showed a high sensitivity to DCCD and diethylstilbestrol (up to 90% inhibition), a complete dependence on Mg(2+), and a strong dependence on K(+) at low concentration; the pH optimum of ATPase was close to 6.5, and the K(m) for ATP-Mg was 0.51 millimolar. ATPase activity was much greater when polar lipids from 24-hour-germinated seeds were added.

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PubMed1982

Homology of Plant Peroxidases: AN IMMUNOCHEMICAL APPROACH.

Antisera specific for the basic peroxidase from horseradish (Amoracea rusticana) were used to examine homology among horseradish peroxidase isoenzymes and among basic peroxidases from root plants. The antisera cross-reacted with all tested isoperoxidases when measured by both agar diffusion and quantitative precipitin reactions. Precipitin analyses provided quantitative measurements of homology among these plant peroxidases. The basic radish (Raphanus sativus L. cv. Cherry Belle) peroxidase had a high degree of homology (73 to 81%) with the basic peroxidase from horseradish. Turnip (Brassica rapa L. cv. Purple White Top Globe) and carrot (Daucus carota L. cv. Danvers) basic peroxidases showed less cross-reaction (49 to 54% and 41 to 46%, respectively). However, the cross-reactions of antisera with basic peroxidases from different plants were greater than were those observed with acidic horseradish isoenzymes (30 to 35%). These experiments suggest that basic peroxidase isoenzymes are strongly conserved during evolution and may indicate that the basic peroxidases catalyze reactions involved in specialized cellular functions. Anticatalytic assays were poor indicators of homology. Even though homology among isoperoxidases was detected by other immunological methods, antibodies inhibited only the catalytic activity of the basic peroxidase from radish.

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PubMed1982

Temperature effects on seed imbibition and leakage mediated by viscosity and membranes.

The possible involvement of membranes and water viscosity in the temperature effects on imbibition and solute leakage of radish (Raphanus sativa var. Early Scarlet Globe) seeds and excised sugar pine (Pinus lambertiana Dougl.) embryos was evaluated. In these two seed materials, the temperature effect on initial rates of imbibition and solute leakage could be accounted for primarily by changes in water viscosity, the relationship being approximately linear. It appears that membranes are involved both in water uptake and solute leakage. Heat-killed radish seeds and sugar pine embryos exhibited significantly higher rates of imbibition and solute leakage than did viable ones. In addition, sugar pine embryos exhibited an abrupt change in rates of imbibition and solute leakage between 15 and 20 degrees C, resulting in abnormally high water uptake and solute leakage above this temperature.

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PubMed1982

Isolation and identification of a new growth inhibitor, raphanusanin, from radish seedlings and its role in light inhibition of hypocotyl growth.

A neutral growth inhibitor, for which the name raphanusanin is proposed, has been isolated in crystalline form from light-exposed Sakurajima radish (Raphanus sativus var. hortensis f. gigantissimus Makino) seedlings and identified as a new compound, 3-methoxy-4-methylthio-2-piperithione by spectrometric analyses.Applied raphanusanin inhibited the hypocotyl growth of etiolated radish and lettuce seedlings at concentrations higher than 1.5 x 10(-6) molar.The endogenous raphanusanin contents in cotyledons and hypocotyls of radish seedlings increased more under red light, but decreased or maintained the initial level in the dark. Its content in roots showed almost no change between the light and dark materials.

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PubMed1983

Invertase activity and the kinetin-stimulated enlargement of detached radish cotyledons.

Cytokinin treatment is known to promote expansion of light-grown excised radish (Raphanus sativus L. cv Crimson Giant) cotyledons. This expansion, at least in part, seems to be related to an increased accumulation of osmotically active reducing sugars. Kinetin treatment did not cause increased levels of isocitrate lyase activity over the controls, but stimulated increased levels of two invertase forms, designated types I and II. Type I was soluble and type II was insoluble after homogenization in 10 millimolar tris(hydroxymethyl)aminomethane-HCl (pH 7.0). Both types were soluble after homogenization in 300 millimolar NaCl. At low salt concentration, type II was retained on a diethylamioethyl-cellulose column and type I was not. Type II was then eluted from the column at high salt concentration. Types I and II exhibited pH optima of 5.3 and 4.3, Michaelis constants of 4.96 and 1.23 millimolar sucrose, and molecular weights of 65,000 and 57,000 daltons, respectively. The kinetin promotion of reducing sugar accumulation may be related to increased levels of the two invertase forms, but is probably not a result of direct cytokinin-stimulated glyoxysomal activity.

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PubMed1984

Utilization of a response-surface technique in the study of plant responses to ozone and sulfur dioxide mixtures.

A second order rotatable design was used to obtain polynomial equations describing the effects of combinations of sulfur dioxide (SO(2)) and ozone (O(3)) on foliar injury and plant growth. The response surfaces derived from these equations were displayed as contour or isometric (3-dimensional) plots. The contour plots aided in the interpretation of the pollutant interactions and were judged easier to use than the isometric plots. Plants of ;Grand Rapids' lettuce (Lactuca sativa L.), ;Cherry Belle' radish (Raphanus sativus L.), and ;Alsweet' pea (Pisum sativum L.) were grown in a controlled environment chamber and exposed to seven combinations of SO(2) and O(3). Injury was evaluated based on visible chlorosis and necrosis and growth was evaluated as leaf area and dry weight. Covariate measurements were used to increase precision. Radish and pea had greater injury, in general, that did lettuce; all three species were sensitive to O(3), and pea was most sensitive and radish least sensitive to SO(2). Leaf injury responses were relatively more affected by the pollutants than were plant growth responses in radish and pea but not in lettuce. In radish, hypocotyl growth was more sensitive to the pollutants than was leaf growth.

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PubMed1984

Developmental regulation of the synthesis of proteins encoded by stored mRNA in radish embryos.

Major radish (Raphanus sativus L. cv National) proteins synthesized at the beginning of germination have been characterized by their migration in two-dimensional electrophoresis.The use of 15-minute labelings shows that these proteins are encoded by stored mRNA. They undergo little or no posttranslational modification. Other proteins become detectable only after 1 hour of imbibition, and are probably encoded by newly synthesized mRNA. Comparison with proteins synthesized during embryogenesis, late germination, or with those present in dry embryos allows the classification of the proteins encoded by stored mRNA into two sets:The first set is synthesized also during late embryogenesis and is present in dry embryos. Some of these polypeptides are no longer synthesized later in germination while the others continue to be synthesized. The corresponding stored mRNAs can be considered as remnants of mRNA actively translated during embryogenesis.The second set is synthesized only during early germination. Their messengers appear during late embryogenesis although they are apparently not translated at this stage, but translation can be induced by a desiccation treatment. These polypeptides may play a particular role during early germination.

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