Plant Protection with Inorganic Ions

Gradients of salts of the specific ion repellents for Meloidogyne incognita -- NH₄⁺, K⁺, Cl⁻, and NO₃⁻ -- have been demonstrated to shield tomato roots from infestation in soil. The strategy of these greenhouse experiments was to interpose a salt barrier in a soil column between the plant roots and the nematodes. The relative effectiveness of the salts as a barrier to infective second-stage juveniles in a sandy loam was NH₄NO₃, NH₄Cl > KNO₃ > KCl. Some of these ions are beneficial to plant growth, and the results suggest that a new environmentally tolerable means of plant protection is possible.     

Uptake of Methylammonium Ions by Hydrodictyon africanum

Methylamine influx into Hydrodictyon has been measured with[^l4C]methylamine. The influx increases with rising externalpH up to about pH 8. Between pH 8 and 9 influx remains quiteconstant, with a further increase above pH 9. Influx is light-dependent,temperature-sensitive, and is decreased by . During short-term influx (less than 4 h) metabolism of methylamineappears negligible. Prolonged influx results in CH₃ accumulation, and efflux of K⁺, Na⁺, and H⁺. There is no effecton Cl^– influx. Methylamine decreases the membrane electricp.d. by 60–120 mV at external concentrations of 0?2–1?0mM. The results indicate that, below pH 9, methylamine enters thecell almost entirely as CH₃. It is suggested that a passive electrogenic uniporter is involved, and thatby analogy uniport of may also be expected in Hydrodictyon. The results are discussed in relation to theevidence for uptake of CH₃ and by other plant cells.     

Efficient Uptake of Cesium Ions by Rhodococcus Cells

Bacteria of the genus Rhodococcus were found to be able to accumulate cesium by means of active transport and nonspecific sorption on the cell surface structures. The maximum removal (up to 97%) of cesium from a medium supplemented with ammonium acetate was observed at 28°C, pH 7.8–8.6, and an equimolar content (0.2 mM) of potassium and cesium ions in the medium. The most active cesium-accumulating rhodococcal strains may be useful in biological treatment of industrial wastewaters contaminated with radionuclides.     

Uptake of Metal Ions by Rhizopus arrhizus Biomass

Rhizopus arrhizus biomass was found to absorb a variety of different metal cations and anions but did not absorb alkali metal ions. The amount of uptake of the cations was directly related to ionic radii of La³⁺, Mn²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Ba²⁺, Hg²⁺, Pb²⁺, UO₂²⁺, and Ag⁺. The uptake of all the cations is consistent with absorption of the metals by sites in the biomass containing phosphate, carboxylate, and other functional groups. The uptake of the molybdate and vanadate anions was strongly pH dependent, and it is proposed that the uptake mechanism involves electrostatic attraction to positively charged functional groups.     

Uptake of Some Quaternary Ammonium Ions by Human Erythrocytes

In many biophysical studies on erythrocytes some quaternary ammonium ions are used as replacements for Na⁺ and K⁺ of the physiological solutions. The object of this work was to study the possible uptake of quaternary ammonium ions by erythrocytes. Uptake of C¹⁴–choline chloride and C¹⁴–tetramethylammonium chloride by human erythrocytes was proved. It was shown that the compounds were neither incorporated into phospholipids of the cell nor converted to any other metabolites. Studies of uptake as a function of time, at several external concentrations of choline and tetramethylammonium, showed that within the first 4 hours uptake was a linear function of time regardless of the external concentration of the quaternary ammonium ions. The effects of various external concentrations of choline and tetramethylammonium ions on the rate of uptake by the cells were studied. The results showed the presence of two distinct mechanisms for the uptake of choline: one, a facilitated uptake mechanism which becomes saturated at low external concentrations of the ion; the other, a simple diffusion mechanism in which the rate of uptake is proportional to concentration. For the facilitated part of the uptake the external choline concentration at which half-maximum rate was obtained was found to be 0.02 mm. Although the kinetic studies with tetramethylammonium ion were not as extensive as those with choline, they did suggest the presence of similar mechanisms for the uptake of both ions. Tetramethylammonium and tetraethylammonium ions were shown to be competitive inhibitors of the facilitated choline uptake.     

Uptake of Proteins by Plant Roots

The patterns of uptake of fluorescein-labelled lysozyme (Fl-lysozyme) by barley, maize, onion, tomato and vetch are similar as revealed by fluorescence microscopy. Penetration of the root cap and through the epidermis into the cortex increases with time of exposure and decreases with higher salt concentrations. In fact, one molar ethylammonium chloride can remove most of the absorbed protein from treated roots and the space observed to be stained by Fl-lysozyme in this manner can be visualized as “free space”. Results with sterile and non-sterile barley roots were indistinguishable. At low ionic strength, Fl-lysozyme can penetrate cells and complex with nucleoli. Such cell protoplasts appear “coagulated”. Uptake results with fluorescein per se were unlike those with protein. The uptake of a much larger molecule, ferritin, is confined to the epidermis and root cell walls. Localized, absorbed protein and root growth inhibition by basic proteins have yet to be related.     

A Topographic Method for Studying Uptake, Translocation and Distribution of Inorganic Ions using Two Radiotracers Simultaneously

A novel topographic method is described for the fully automatedquantitative resolution of activity of two simultaneously appliedbeta tracers in plant tissues. The advantages of this methodusing specially developed silicon detectors are demonstratedin studying the effect of direct current on the uptake and distributionof Ca²⁺ and P₁ ions in leaves and stems of Chenopodium rubrum.This treatment has recently been shown to inhibit flower inductionin this plant. Key words: Radiotracer multi-labelling, computer-controlled resolution, quantitative topographic evaluation     

The Relationship between Transpiration and the Absorption of Inorganic Ions by Intact Plants

The relationship between the rate at which water and the rubidiumand phosphate ions are absorbed by intact plants, and transferredto their shoots has been investigated in water culture undervarying conditions of transpiration and nutrient supply. When the external concentration and the nutrient status of theplants are sufficient low, wide variations in the rate of transpirationhave little effect on the transfer of nutrients to shoots; whenlittle water is being lost by transpiration the concentrationin the transpiration stream may exceed that in the externalmedium by factors exceeding 100. In contrast when the externalconcenration and the nutrient status of the plants are highthe rate of transfer of ions to shoots may vary closely withthe rate of transpiration and the concentration in the transpirationstream may be similar to, or less then, that in the externalmedium. The occurrence of concentrations of ions in the roots is transpirationstream which greatly exceed those in the medium external tothe roots is regarded as evidence that ions not transferredpassively across the roots of intact plants to a significantextent.     

Uptake and Accumulation of Inorganic Carbon by a Freshwater Diatom

Colman, B. and Rotatore, C. 1988. Uptake and accumulation ofinorganic carbon by a freshwater diatom.—J. exp Bot 39:1025–1032. The mechanism of uptake of inorganic carbon and its accumulationhas been studied in the freshwater diatom Navicula pelliculosa.No external carbonic anhydrase could be detected, although itwas detected in cell extracts. The rate of photosynthetic O₂evolution, in media in the range pH 7.5–8.5, exceededthe calculated rate of CO₂ supply 2- to 5-fold, indicating thatHCO^–₃ was taken up by the cells. At an external pH of7.5, the internal pH, measured by ¹⁴C-dimethyloxazolidine-2,4-dione distribution between the cells and the medium, was pH7.6 in the light and pH 7.4 in the dark. Accumulation of inorganiccarbon was determined by the silicone oil centrifugation methodand inorganic carbon pools of 23.5 mol m^–3 were found,a concentration 21.6-fold that in the external medium. The resultsindicate an active accumulation of inorganic carbon againstpH and concentration gradients in this diatom, probably by activeHCO^–₃ uptake. Key words: Bicarbonate transport, carbon dioxide, carbonic anhydrase, CO₂ affinity, CO₂ concentrating mechanism, internal pH, Navicula pelliculosa     

The Relation between the Synthesis of Inorganic Polyphosphate and Phosphate Uptake by Chlorella vulgaris

During a period of phosphate starvation, the phosphate contentof cells of Chlorella vulgaris which had been grown in phosphate-richsolution, decreased. The levels of most phosphate fractionsdeclined, especially those of inorganic polyphosphates, whichat first accounted for about 5 per cent of the total phosphateand virtually disappeared after 36 h starvation. On return toa phosphate medium, phosphate was taken up at a much fasterrate than before starvation, with a striking increase in acid-solublepolyphosphate. The stimulated phosphate uptake and polyphosphateincrease have been shown to be specific effects of phosphatestarvation, occurred only when excess phosphate was suppliedand required light or air for the provision of energy. Therewas relatively little change in the concentrations of otherphosphate fractions, including orthophosphate. Inorganic polyphosphatewas found to be synthesized solely from phosphate absorbed fromthe medium. It is argued that polyphosphate synthesis is a consequenceof the stimulation of phosphate uptake, induced by the starvationperiod.     

The Initial Uptake of Ions by Barley Roots: I. UPTAKE OF ANIONS

Experiments have been carried out to examine the applicabilityof the Goüy–Chapman electrical double-layer theoryto the initial entry of anions into excised barley roots. Anattempt was made to separate the total quantity of labellediodide or sulphate ions which had entered the roots under varyingconditions into three fractions: the two fractions which couldbe successively eluted with water and extracted with an exchangingsolution and that which remained in the roots after these treatments.Except at a low temperature and a low hydrion concentration,the three fractions could not clearly be distinguished, andthere were indications of the presence of metabolically maintainedpositive sites. However, the effect of varying pH on the rateat which anions were eluted with water was consistent with thepresence in the roots of a system of pores, the walls of whichcarried a varying number of negative charges depending on thehydrion concentration. The effect of calcium ions on the magnitudeof the water extractable fraction also accorded qualitativelywith the double-layer theory.     

枸杞体细胞胚发生中对痕量金属离子吸收的动态研究

以药用植物宁夏枸杞（Lycium barbarum L.)愈伤组织为材料,离体培养诱导体细胞胚发生,采用多重示踪技术和γ射线能谱分析法研究枸杞研究枸杞体细胞胚发生中对多种痕量金属离子的吸收动态,结果表明：（1）体胚发生中对多种痕量金属离子的吸收呈选择性。对多重示踪剂溶液中的23种核素,只吸收了其中的16种（Mn-52,Zn-65,Co-56,Co-60,As-74,mTc-95,Rh-99,V-48,Rb-83,Rb-84,Sr-85,Y-87,Y-88,Zr-88,Zr-89),而对另7种未吸收（Be-7,Tc-96,Ru-97,mRh-101,Sc-46,Ga-67和Cr-51)。（2）吸收呈动态变化,在同一发育期对不同的金属离子吸收率不同,如第10天,大部分金属离子的吸收率在5％／g左右,而se-75,Rb-83,Sr-85,Zr-89的则是10％－30％/g,在不同发育期对同一种金属离子的吸收率不同,如对Se-75的吸收总体呈上升趋势。第5天达第1峰值14％/g。随后缓慢下降,基本稳定,第15天后急剧上升,至第20天达第2个峰值20％／g;随着胚性细胞的分化与分裂,吸收既存在一致性,也存在非一致性。Se-75,Rb-83,Sr-85,Co-56和V－48等核素的吸收趋势相似,基本上呈上升曲线,而Mn-52的吸收趋势则类似正态分布曲线。     

The Initial Uptake of Ions by Barley Roots: III. THE UPTAKE OF CATIONS

Experiments have been carried out to determine the extent towhich rubidium and strontium, recently absorbed by excised barleyroots, can be divided into discrete fractions, namely, ionswhich are extractable with water, those which are exchangeable,and those remaining in the tissue at the end of the experiment.The object of this study was to determine whether the behaviourof cations could be validly interpreted in terms of the electricaldouble-layer theory as had been previously demonstrated foranions. To facilitate the interpretation of the results obtained, comparableexperiments were carried out on a cation-exchange resin andon gelatin. The behaviour of strontium accorded qualitatively with the theoryproviding allowance was made for effects due to the hydrolysisof negative sites and for the presence of positive charges inthe roots. For rubidium, on the other hand, the situation was much morecomplex. Not only was there evidence even at 0.2°C for siteswhich retained a high specificity for this ion, but also movementof the ion due to physical diffusion was masked by concurrentmetabolic activity. It was concluded that a meaningful separation of the over-alluptake of rubidium into successive steps of exchange absorptionand metabolic accumulation cannot be made.