Acclimation to low temperature by microsomal membranes from tomato cell cultures

Sealed vesicles were prepared from microsomal membranes from cell suspension cultures of tomato (Lycopersicon esculentum Mill cv VF36). ATP-dependent proton transport activity by the vesicles was measured as quenching of fluorescence of acridine orange. Measurements of proton transport were correlated with the activity of a nitrate-inhibitable ATPase. The initial rate of proton influx into the vesicles was strongly temperature dependent with a Q₁₀ of 2 and a maximum rate near 35°C. The data suggest that passive permeability did not increase at chilling temperatures but did increase rapidly with temperatures above 30°C. A comparison was made between membranes from cell cultures grown at 28°C and 9°C. The temperature optimum for proton transport broadened and shifted to a lower temperature range in membranes from cells maintained at 9°C.     

Effect of temperature on bacterial gellan production

The effect of temperature on the production of the polysaccharide gellan by the bacterium Sphingomonas paucimobilis ATCC 31461 was studied in relation to carbon source. When glucose served as the carbon source, gellan formation by the strain was highest after 72 h of growth at an incubation temperature of 30–31 °C. Polysaccharide production by the sphingomonad cells grown on corn syrup for 72 h was maximal at an incubation temperature of 31 °C. The highest cellular productivity in elaborating gellan was observed at 31 °C after 72 h of growth independent of the carbon source utilized.     

The rapid dissolution of dioecy by experimental evolution

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Symbiotic effectiveness of Rhizobium meliloti at low root temperature

Laboratory, growth chamber and field experiments were conducted to select among 226 isolates of Rhizobium meliloti for the ability to grow, nodulate alfalfa (Medicago sativa L.) and support N₂-dependent plant growth between 9° and 12°C. There was wide variation in the abilities of R. meliloti isolates to grow and form nodules at 10°C. Culture doubling times (t_d) varied from 1 to 155h, and the number of nodules formed on alfalfa in growth pouches in 2 weeks varied from 0 to 3.8 nodules per plant. Nodulation occurred at 9°C, but there was no significant N₂-dependent plant growth at this temperature. However, several isolates of R. meliloti had the ability to nodulate alfalfa and produce N₂-dependent growth at root temperatures between 10° and 12°C root temperature than did 14 other isolates tested. In field experiments, inoculation with strain NRG-34 resulted in greater nodule numbers, nodule weight, proportion of nodules occupied by the inoculant strain and plant weight than did inoculation with a commercial strain (NRG-185). These results permitted selection of a strain with better low-temperature competitive abilities than the currently available commercial strains.     

Rapid acclimation of root hydraulic conductivity to low temperature

Root hydraulic conductance of many species is substantially reduced by exposure to low temperatures. The objective of this research was to investigate the decrease and recovery of root hydraulic conductivity in spinach (Spinacia oleracea L.) root systems upon exposure to low temperature. Root hydraulic conductivity (Lp) was determined for detached whole root systems as the slope of the flux and an applied pressure gradient. Water flux (Jv), of root systems grown at 20C, decreased immediately upon exposure to 5C. After 2-5 h Jv recovered and reached a stable value after 12 h exposure to 5°C. In separate experiments, the root Lp of plants acclimated for 7 d at 5°C was 125% greater than that of isolated root systems acclimated for 12 h at 5°C. Lp of plants grown and measured at 5°C was about 50% of the Lp of plants grown and measured at 20°C. The rapid acclimation to low temperatures observed in detopped root systems was also indicated in intact plants at 20/5°C (shoot/root temperatures) using mass flow porometry. Acclimation of the root system after exposure to 5°C was apparent by recovery of stomatal opening. These results indicate that spinach root systems have the ability to acclimate rapidly to changes in temperature and to continue acclimating during prolonged exposure to low temperature.     

Flavonoids from Glycyrrhiza pallidiflora hairy root cultures

Three flavonoids named licoagrosides D, E and F together with four known flavonoids, medicarpin 3-O-glucoside, calycosin 7-O-glucoside, formononetin 7-O-(6"-malonylglucoside) and 2'-hydroxyformononetin 7-O-glucoside were isolated from Glycyrrhiza pallidiflora hairy root cultures. Their structures were determined on the basis of spectroscopic evidence. Licoagrosides E and F are the first examples of a 6a-hydroxypterocarpan glycoside and an alpha-O-glycosidic alpha-hydroxydihydrochalcone, respectively.     

Flavonoids from Glycyrrhiza pallidiflora hairy root cultures

Glycyrrhiza pallidiflora hairy roots were induced from axenic young plants by direct infection with Agrobacterium rhizogenes. The chemical constituents were then investigated after mass culture. The isoflavone, licoagroisoflavone and the coumestan, licoagroside C, were isolated along with seven known flavonoids. Their structures were determined on the basis of spectroscopic evidence.     

Absorption of nitrate and ammonium ions by Lolium perenne from flowing solution cultures at low root temperatures

Lolium perenne L. cv. 23 (perennial ryegrass) plants were grown in flowing solution culture and acclimatized over 49 d to low root temperature (5°C) prior to treatment at root temperatures of 3, 5, 7 and 9°C for 41 d with common air temperature of 20/15°C day/night and solution pH 5·0. The effects of root temperature on growth, uptake and assimilation of N were compared with N supplied as either NH₄ or NO3 at 10 mmol m^?3. At any given temperature, the relative growth rate (RGR) of roots exceeded that of shoots, thus the root fraction (Rf) increased with time. These effects were found in plants grown with the two N sources. Plants grown at 3 and 5°C had very high dry matter contents as reflected by the fresh weight: freeze-dried weight ratio. This ratio increased sharply, especially in roots at 7 and 9°C. Expressed on a fresh weight basis, there was no major effect of root temperature on the [N] of plants receiving NHJ but at any given temperature, the [N] in plants grown with NHJ was significantly greater than in those grown with NO₃. The specific absorption rate (SAR) of NH⁺₄ was greater at all temperatures than SAR-NO₃. In plants grown with NH⁺, 3–5% of the total N was recovered as NH⁺₄, whereas in those grown with NO^?₃ the unassimilated NO^?₃ rose sharply between 7 and 9°C to become 14 and 28% of the total N in shoots and roots, respectively. The greater assimilation of NH⁺₄ lead to concentrations of insoluble reduced N (= protein) which were 125 and 20% greater, in roots and shoots, respectively, than in NO^?₃-grown plants. Plants grown with NH⁺₄ had very much greater glutamine and asparagine concentrations in both roots and shoots, although other amino acids were more similar in Concentration to those in NO^?₃ grown plants. It is concluded that slow growth at low root temperature is not caused by restriction of the absorption or assimilation of either NH⁺₄ or NO^?₃. The additional residual N (protein) in NH⁺₄ grown plants may serve as a labile store of N which could support growth when external N supply becomes deficient.     

Flavonoid constituents from Glycyrrhiza glabra hairy root cultures

An unusual biflavonoid named licoagrodin was isolated from the hairy root cultures of Glycyrrhiza glabra (Leguminosae) along with three prenylated retrochalcones, licoagrochalcones B, C, D, a prenylated aurone, licoagroaurone and four known prenylated flavonoids, licochalcone C, kanzonol Y, glyinflanin B and glycyrdione A. From the glycosidic fraction, a isoflavone glycoside, licoagroside A, and a maltol glycoside, licoagroside B were isolated together with four known isoflavone glycosides, two flavone C-glycosides, and three other glycosides. Their structures were elucidated on the basis of spectroscopic evidence.     

The effect of temperature on hairy root cultures of Catharanthus roseus: Growth,indole alkaloid accumulation and membrane lipid composition

Cultivation of Catharanthus roseus hairy root cultures at different temperatures was found to have an effect on growth rate and indole alkaloid content as well as lipid composition. When lowering the temperature, the roots responded by increasing the degree of unsaturation of cellular lipids, which was mainly due to an increased proportion of linolenic acid in the main lipid classes. The modifications in lipid composition were obviously necessary for the roots to retain the proper cell membrane fluidity at each temperature. Despite of changes in membrane lipids, no effect on the distribution of indole alkaloids between the roots and the medium could be detected. Instead, the level of alkaloid accumulation showed a clear increase with lowering temperature.Abbreviations PC phosphatidylcholine - PE phosphatidylethanolamine - PI phosphatidylinositol - PS phosphatidylserine - PG phosphatidylglycerol - CL cardiolipin - DGD digalactosyldiglyceride - MGD monogalactosyldiglyceride - NL neutral lipids - DU degree of fatty acid unsaturation     

Texture properties of high and low acyl mixed gellan gels

The strength, deformability, and firmness of high acyl (H) and low acyl (L) mixed gellan gels were studied by compression tests. The gels were prepared with total polymer concentrations of 0.5, 1.0, and 1.5% at H/L weight ratios of 25/75, 50/50, 75/25, and calcium concentrations 2–80 mM. The mixed gels were much more deformable, with failure normal strains ranging from 0.6 to 1.5, but had similar strength compared to low acyl gellan gels. Both H/L ratio and total polymer concentration affected the textural properties, but H/L ratio was a more important factor. Maximum synergistic interaction was observed at H/L=50/50. The mixed gels exhibited excellent texture properties compared to other common food gels.     

A simple rapid procedure for obtaining axenic cultures from monoxenic cultures of myxomycete plasmodia

Axenic culture of myxomycete plasmodia has been attempted from time to time by various authors, but with very little success. From over 500 known species of myxomycetes, fewer than 20 species have been reported in axenic culture to date, including axenic myxamoebal cultures. In these cultures, the plasmodia required either complex media, or a killed bacterial supplement for growth. Furthermore, the time required for attaining the axenic state varied from several months to years. In the present study, a simple, rapid procedure has been developed to render monoxenic plasmodial cultures axenic. This procedure is based on our discovery that plasmodia have certain unusual substrate preferences that are inhibitory to the associated bacteria using Physarella oblonga as a model. The presence or absence of the bacteria could be ascertained through incubation in four different bacteriological media and by the use of a differential staining technique.     

Influence of low air humidity and low root temperature on water uptake, growth and aquaporin expression in rice plants

The effects of low air humidity and low root temperature (LRT) on water uptake, growth and aquaporin gene expression were investigated in rice plants. The daily transpiration of the plants grown at low humidity was 1.5- to 2-fold higher than that at high humidity. LRT at 13°C reduced transpiration, and the extent was larger at lower humidity. LRT also reduced total dry matter production and leaf area expansion, and the extent was again larger at lower humidity. These observations suggest that the suppression of plant growth by LRT is associated with water stress due to decreased water uptake ability of the root. On the other hand, the net assimilation rate was not affected by low humidity and LRT, and water use efficiency was larger for LRT. We found that low humidity induced coordinated up-regulation of many PIP and TIP aquaporin genes in both the leaves and the roots. Expression levels of two root-specific aquaporin genes, OsPIP2;4 and OsPIP2;5, were increased significantly after 6 and 13 d of LRT exposure. Taken together, we discuss the possibility that aquaporins are part of an integrated response of this crop to low air humidity and LRT.     

Eugenol from normal and transformed root cultures of Coluria geoides

Transformed root cultures of Coluria geoides Ledeb. were established with the use of Agrobacterium rhizogenes LBA 9402. Both normal and transformed root cultures were investigated for their growth and yield of eugenol. Normal roots were grown in B5 medium-supplemented with 0.2 mg l^-1 of kinetin and 0.2 mg l^-1 of 1-naphthaleneacetic acid (NAA). Hairy roots grew well in hormone-free B5 medium. Both hairy roots and normal roots produced glycosidic bound eugenol. as with the roots of intact plants, eugenol was the main component of the total essential oils obtained from hairy root and normal root cultures. The yield of eugenol from normal roots was 0.1–0.25% of the dry wt. and depended on the development stage of the culture. Yield of eugenol from hairy roots was 0.08–0.1% of the dry wt. NAA modified the hairy root morphology and influenced the yield of eugenol.Abbreviations NAA 1-naphthaleneacetic acid     

Chilling root temperature causes rapid ultrastructural changes in cortical cells of cucumber (Cucumis sativus L.) root tips

Examination of root tips from cucumber (Cucumis sativus L.) seedlings grown at 8 degrees C for varying periods ranging from 15 min to 96 h, showed marked changes in the ultrastructure of cortical cells within only 15 min of exposure. Greater parts of the cortex were affected with longer periods of exposure, but the sequence of morphological changes in cell components was similar to that found for the roots exposed for 15 min. The effect of chilling injury included alterations in cell walls, nuclei, ER, mitochondria, plastids, and ribosomes. The extent of alterations varied greatly among cells, moderate to severe alterations to cell components being observable among adjoining cells. The measurements of root pressure using the root pressure probe showed a sudden, steep drop in the root pressure in response to lowering of the temperature of the bathing solution from 25 degrees C to 8 degrees C. These observations are discussed in the light of the information available on the ultrastructural and biochemical characteristics of the effect of cold exposure in chilling-sensitive plants.