The Absorption and Accumulation of Salts by Living Plant Cells: IX The Absorption of Rubidium bromide by Potato Discs

Chemical methods for the quantitative determination of rubidiumin aqueous plant extracts and saps were investigated but abandonedin favour of a spectrographic technique which is fully described. The results of quantitative determinations of the rubidium andbromide absorbed by potato discs from solutions of rubidiumbromide, and the effects upon this absorption of oxygen, oftime, and of the specific surface of the discs are described.The effects of these variables upon the accumulation of bromidewhich were previously described have been confirmed. All thevariables which affect bromide absorption affect the uptakeof rubidium in a similar manner. The absorption of rubidium is of two distinct kinds. The firstphase in the absorption process is a relatively rapid uptakeof rubidium unaccompanied by bromide. This process is unaffectedby oxygen, is not confined to the surface cells, and ceasesafter a short time. The second phase occupies a protracted periodduring which both rubidium and bromide are absorbed in equivalentamounts. During this phase the absorption is confined to a fewlayers of cells at the surface and is determined by oxygen concentrationin the manner already described for the bromide ion. The two types of absorption are described as ‘inducedabsorption’ and as ‘primary absorption’ inthe sense used earlier. The former is merely a property of thesubstances in the tissue, the latter is a process which tendsto increase the free energy of the tissue, therefore demandsthat work should be done, and is a property of the organizedliving cell. The relationships of the two types of absorption process totime have been described and they can be expressed in termsof equations. The effect of the surface and thickness of discs upon the absorptionof bromide and rubidium is interpreted quantitatively. The distance from the surface of the discs at which ‘primaryabsorption’ ceases is the same for rubidium and bromide,and coincides with the values previously determined for thedepth of the layer of tissue which exhibits enhanced respiration. The ‘induced absorption’ of rubidium may be observedin discs killed by alcohol. The effect of concentration uponthis process is similar to the adsorption isotherm. The effectof concentration upon the absorption of bromide by living discsis much less conspicuous and the requirements of the absorptionisotherm are not rigidly met. The effect of concentration alsoinvolves the factor of surface and thickness of disc. Unequal absorption of the bromide and rubidium arises from thesuperimposed effect of two distinct processes one of which causesthe absorption of rubidium only and the other tends to causeequal uptake of rubidium and bromide.     

Effect of Nitrate Concentration on the Root: Shoot Ratio in Dactylis glomerata L. and on the Kinetics of Growth in the Vegetative Phase

The vegetative growth of Dactylis glomerata L. in sand was studiedunder controlled light, temperature, and nutritional conditions.Plants were daily supplied with three nutrient solutions ofdifferent nitrate concentrations (10^–2, 10^–3 and2 x 10^–4 mol I^–1). For each concentration, growthobeyed an exponential law between the fourth and seventh weeksafter sowing. The time constant of the exponential was the samefor the shoot as for the root, and showed no significant variationwith nitrate concentration. The kinetic results and the strong dependence of the root: shootratio on nitrate concentration are discussed on the basis ofThornley's model. Hypothesizing that the molecular mechanismsof nitrate absorption are independent of the nitrate concentrationof the nutrient solution, we derived a relationship betweenthe root: shoot ratio and nitrate concentration. This relationshipwas found to be compatible with the experimental results. Dactylis glomerata L., vegetative phase, kinetics of growth, root: shoot equilibrium, nitrate absorption     

Influence of Root and Content on the Temperature Response of Net and Uptake in Chilling Sensitive and Chilling Resistant Lycopersicon Taxa

We studied the influence of internal ammonium and nitrate contenton the temperature response of ammonium and nitrate uptake inboth chilling sensitive and chilling resistant tomatoes. Threetaxa were examined: Lycopersicon esculentum Mill. cv. T-5, achilling sensitive cultivar, Lycopersicon hirsutum Humb. andBompl. LA 1264, a wild, chilling sensitive accession from thelowlands of Ecuador, and Lycopersicon hirsutum LA1778, a chillingresistant accession from the highlands of Peru. Short exposures(4 h) of L. esculentum cv. T-5 to chilling temperatures irreversiblyinhibited ammonium absorption for at least 6 h. Nitrate absorptionin this taxon and ammonium and nitrate absorption in the L.hirsutum accessions recovered fully and immediately from suchexposures. The chilling resistant accession, L. hirsutum LA1778,showed a lower Q₁₀ for ammonium absorption (1?54?0?10, mean?s.e.)than its chilling sensitive relatives, L. hirsutum LA1264 (2?37?0?35)and L. esculentum cv. T-5 (1?92?0?11). The temperature responseof nitrate absorption depended on internal nitrate status; plantsgrown at high levels of ammonium and nitrate (200 mmol m^–3)showed higher Q₁₀'s for nitrate uptake (2?29?0?10) than thosedepleted of internal (1?86?0?12). Key words: Lycopersicon, ammonium, nitrate, temperature response, chilling     

Studies in the Physiology of Lichens: With one Figure in the Text: Absorption and Utilization of Some Simple Organic Nitrogen Compounds by Peltigera polydactyla

Peltigera discs can accumulate relatively very large amountsof asparagine from solution by a process which involves theentry and accumulation of asparagine in the tissues as the completemolecule. Utilization of absorbed asparagine occurs at a relativelyslow rate and involves the preliminary deamidation of it toammonia. Asparagine absorption is completely inhibited by sodiumfluoride, and partially inhibited by glucose. Absorption isaccompanied by a release of ammonia in the medium and also byincreases in respiration rates and a change in R.Q. None ofthe absorbed asparagine can be washed out of the tissues. Discsalso show strong powers of absorption from solutions of glutamine,and glutamic and aspartic acids. There is more organic thaninorganic nitrogen in solution in the liquids available to thelichen in its habitat. The amounts of glucose and of phosphate which Peltigera andsome other lichens can accumulate from solution are also verylarge considering the slow growth-rates of these plants. Itis suggested that the possession of strong powers of absorptionof substances from solution may be a general characteristicof lichens and plants of similar habitats: it may representan adaptation to existence in barren conditions where the concentrationof nutrients in solution is very low. Utilization of absorbednutrients at a slow rate may be an adaptation to the need tosurvive long periods of starvation. The ecological implicationsof these suggestions are also discussed.     

Studies in the Physiology of Lichens: With two Figures in the Text: The Effects of Starvation and of Ammonia Absorption upon the Nitrogen Content of Peltigera polydactyla

Discs cut from the thallus of the lichen Peltigera polydactylacontain relatively large amounts of ammonia nitrogen and smallamounts of amide nitrogen. During starvation in the dark theamounts of ammonia and amide nitrogen remain unchanged, butthe amount of amino-nitrogen increases. Absorption of ammoniaresults in increases in the amounts of ammonia and amino-nitrogenin the discs, but not in the amount of amide nitrogen. It istherefore concluded that amides do not have an important quantitativerole in the nitrogen metabolism of the discs. Ammonia absorption is stimulated by addition of glucose to themedium, but the very slow rate of protein synthesis is onlyslightly increased by glucose. The rate of nitrate absorptionis much slower than that of ammonia absorption. The ecological implications of the results are discussed, andexisting knowledge of the nitrogen metabolism of lichens isreviewed.     

Comparative multifunctional properties of partially carboxymethylated cotton gauze treated by the exhaustion or pad-dry-cure methods

A commercial cotton gauze was modified by partial carboxymethylation using both exhaustion and pad-dry-cure methods, and varying the reaction time and concentration of monochloroacetic acid and sodium hydroxide to obtain the relative degree of carboxymethylation differently. For each experiment, relative value of the degree of substitution (DS_rel) of the modified cotton was evaluated and compared with whole blood clotting time, absorption and retention of chitosan and silver nitrate solutions, antibacterial activity, and physical properties of whiteness, bursting strength and water absorption. Carboxymethylated cotton gauze with a higher DS_rel value showed a better absorption of chitosan and silver nitrate solutions and retained these two solutions for a much longer time than those of unmodified cotton gauze or carboxymethylated cotton gauze at a lower DS_rel. Carboxymethylated cotton gauzes obtained from exhaustion method showed significant antibacterial activity and higher bursting strength and less affected whiteness index than those treated by pad-dry-cure method.     

Absorption of Cadmium and Lead Ions by Gametophyte of the MossPlagiomnium undulatum

A cytochemical analysis of heavy-metal distribution was used to establish an increased ability of the marginal and midrib cells of moss leaves to accumulate metal ions from solutions of lead and cadmium nitrate. The adjacent leaf cells accumulated metal ions more slowly. As shown by the color reaction produced by metal–dithizone complex, the concentration of the absorbed metal ions in the cells increased more than 100-fold as compared to the salt concentration in the solution. The morphological differentiation of the marginal and midrib cells was closely related to the cytosolic pH value and the absorption capacity of cells. Metal ions absorbed in excess of the capacity of absorption sites were not bound by cells and readily washed out.     

Responses of nitrate assimilation and N translocation in tomato (Lycopersicon esculentum Mill) to reduced ambient air humidity

The impact of low humidity in ambient air on water relations,nitrate uptake, and translocation of recently absorbed nitrogen,was investigated in 5-week-old tomato (Lycopersicon esculentumMill cv. Ailsa Craig) plants grown hydroponically in a completenutrient solution. Plants were subjected to dry air (relativehumidity 2–4% for 6 h. The transpiration rate increasedseveral-fold and the shoot water content decreased by almost20%, whereas root water content was unaffected. No effect onin vitro nitrate reductase (NR) activity was detected when usingan EDTA-contraining assay buffer. Replacement of EDTA with Mg²⁺revealed a significant decline in shoot NR activity, which suggestsphosphorylation of the enzyme during the stress treatment. Plantswere grown in a split-root system, in which one root half wasfed ¹⁵N-nitrate during the treatment, in order to determinenitrate uptake and translocation of recently absorbed nitrogenin the plants. Uptake of nitrate was substantially inhibited,but the proportion of absorbed ¹⁵N that was translocated tothe shoots was only slightly affected. In untreated plants,71% of the ¹⁵N recovered in roots had been retranslocated fromthe shoots, whereas in plants subjected to stress the deliveryof ¹⁵N from shoots to roots appeared to be completely inhibited.The data show that lowered humidity in air has significant effectson both uptake of nitrate as well as translocation of nitrogenwithin the plants. Some of these effects appear to be commonwith those observed in plants subjected to reduced water potentialsin the root environment and point to the possibility of theshoot water relations being highly influential on nitrogen uptakeand translocation. Key words: Air humidity, nitrate assimilation, nitrate reductase activity, nitrogen translocation, tomato, water stress     

Production and absorption of nitric oxide gas in the nose

Some nitric oxide gas (NO) produced in thesinuses and nasal cavity is absorbed before leaving the nose. Tomeasure production and absorption, we introduced NO at differentconcentrations into one nostril while sampling the NO leaving theopposite nostril with the soft palate closed. The quantity of NO gasproduced in six normal subjects (amount leaving plus the amountabsorbed) averaged 352 nl/min and was the same at gas flows rangingfrom 8 to 347 ml/min and at 10 l/min. An absorption coefficientA was calculated by dividing theamount of NO absorbed by the concentration leaving the nose.A ranged from 17 ml/min at a nasal gasflow of 8 ml/min to an A of 24 ml/minat a nasal gas flow of 347 ml/min. The calculated rates of productionand absorption did not change when gas flow rate was increased,suggesting diffusion equilibrium. The amount of uptake of NO in thenasal mucosa can be explained by its solubility coupled with tissue andblood reactivity.

     

Nitrogen metabolism in tomato seedlings

Tomato seedlings absorbed increasing amounts of nitrate-N. The total uptake was doubled as the concentration of nitrate was quadruplicated. NO₃?N absorption seemed to be accompanied by efflux of OH^? ions which shift the pH of the media to the alkaline side. A minor fraction of the absorbed nitrate accumulated in the tissues while the major part was assimilated into peptides and proteins. The dry matter gain was by the end of experiment relatively higher than the control samples raised on nitrogen-free nutrient solution. Nitrate assimilation seemed to involve its reduction down to ammonia level. Since neither nitrite nor ammonia was recovered in the tissue-medium system, it was postulated that the rate of reduction was slower than the rate of product assimilation. The first step in nitrate reduction (nitrate→nitrate) appeared to be limiting while further reduction steps occurred rapidly and accompanied by simultaneous assimilation of ammonia. The enzyme responsible for the first step of nitrate reduction,i.e., nitrate reductase, was extracted from tomato shoots and roots. The activity in root extract amounted to about 30% of that of the shoot. This may suggest the localization of nitrate reduction in the leaves and realizes the relation between nitrate metabolism and photosynthesis.     

Flower Induction by Suppression of Nitrate Assimilation in Lemna paucicostata 6746

In vitro activity of nitrate reductase was studied in Lemnapaucicostata 6746 grown on modified Hoagland medium supplementedwith 1% sucrose, containing various inhibitors. Copper, silver,tungstate or cyanide which induces daylength-independent flowering,inhibited the nitrate reductase activity, but azide which doesnot induce daylength-independent flowering did not. Molybdate-deficientmedium induced flowering, and inhibited nitrate reductase activity.Lowering of nitrate level of the medium also induced daylength-independentflowering. These results suggest that the suppression of nitrate assimilationcauses daylength independent flowering in Lemna paucicostata6746, and that one of the flower-inducing actions of the copper,silver, tungstate, cyanide or the deletion of molybdate is tosuppress the nitrate assimilation. (Received June 26, 1985; Accepted October 30, 1985)     

Histochemical Differentiation of Chloride from Other Ions Precipitated by Silver Nitrate in Freeze-Substitution Fixation

The method is based on substitution fixation at —25° C of quickly frozen tissue with a 90% alcohol solution saturated with silver nitrate. The silver salts are photochemically reduced in the histological preparations. At this low temperature very little staining of the protein structure of the tissue takes place. Silver ions adsorbed by the tissue can be removed by treatment with a sodium nitrate solution. About 2/3 of the brown material in the histological preparations of cerebral cortex was due to the chloride in the tissue, 1/6 to the phosphate, 1/10 to an unidentified (probably organic) anion, and 1/20 to bicarbonate. When the alcoholic silver nitrate solution used for the fixation is acidified, or the sections are treated with nitric acid, the colored material consists of reduced silver chloride only. A comparison of the light absorption in histological preparations of cortex treated with neutral and with acid solutions supported the conclusion that about 2/3 of the colored material in the tissue is reduced silver chloride.     

Mechanism of Prophylaxis by Silver Compounds against Infection of Burns

To clarify tthe mechanism by which local application of silver compounds protects burns against infection, an ion-specific electrode was used to measùre the concentration of silver ions in solutions. By this method it was shown that in burn dressings silver ions were reduced to a very low level by precipitation as silver chloride. The antibacterial effect was found to depend on the availability of silver ions from solution in contact with precipitate. Between 10^-5 and 10^-6 molar silver nitrate solution in water was rapidly bactericidal. The minimal amount of silver nitrate causing inhibition of respiration of skin in tissue culture was about 25 times the minimal concentration of silver nitrate that inhibited growth of Pseudomonas aeruginosa.     

Absorption of Copper by Lemna as Influenced by Some Factors Which Nullify the Copper Effect on Flowering and Growth

The effect of copper on flowering and growth of Lemna paucicostata6746 and Lemna gibba G3 in a copper-containing medium is nullifiedby the addition of EDTA, ammonium ions or salicylic acid tothe medium or a decrease in its nitrate concentration. Thesefactors were examined for their effects on the absorption ofcopper by the plants. The addition of EDTA to the medium completelyinhibited the absorption of copper in both species, thus eliminatingthe copper effect. Ammonium ions also inhibited copper absorption,their effectiveness rising with their concentration. Loweringthe nitrate concentration in the medium nullified the coppereffect on flowering in L. paucicostata 6746, and the additionof salicylic acid to the medium also nullified the copper effectin L. gibba G3, both without affecting the absorption of copper. (Received June 7, 1982; Accepted August 27, 1982)     

Pre-emergence Growth of Genotypes of Sugarbeet (Beta vulgaris L.) Tolerant to Rhizomania

Growth during pre-emergence of three sugarbeet genotypes, alltolerant to the root disease rhizomania but with poor emergencefeatures, was studied. Dry mass, carbon and nitrogen content,and N isotope composition were measured for the seeds and eachseedling part. These results were compared with those obtainedfor Vega, a genotype with no emergence problems. The depletionof seed reserves and carbon use were similar for all genotypes.Tolerant genotypes had altered nitrogen absorption: the netnitrogen balance (total N in the seedling/N initial mass inthe seed) was 20% lower in these genotypes at the end of theexperiments. Differences in the natural abundance of¹⁵N in seedsand nutrient solutions were used to determine the proportionof N originating from seed reserves or from absorption by theorgans. N absorbed from the nutrient solution was found mainlyin the hypocotyl and radicle, with less in the cotyledons ofall genotypes. Tolerant genotypes had less absorbed N in allparts than non-tolerant genotypes. Hypocotyl and radicle elongationwas the same in all genotypes, but the emergence forces in rhizomania-tolerantgenotypes were smaller. These results suggest that breedingto introduce tolerance to rhizomania has also led to a loweredmineral absorption capacity. Copyright 2000 Annals of BotanyCompany Beta vulgaris L, carbon, nitrogen isotopic composition, rhizomania, seedling growth, seed reserves, sugarbeet.     

Transport of Nitrate and Calcium into Legume Root Nodules

Nitrate transport into nodulated plants of soybean (Glycinemax), cowpea (Vigna unguiculata) and faba bean (Vicia faba)was investigated. Nitrate entering the root system of soybeandid not pass out of the vascular system into nodular tissuesin detectable quantities. On the other hand, nitrate could passfrom soil through the outer surface of nodules but did not penetratethe infected tissue. Similarly, nitrate was restricted to corticaltissues of cowpea and faba bean. Thus, nitrate cannot inhibitnitrogen fixation as a result of reduction to nitrite by nitratereductase within the bacteroid zone. These results are, however,consistent with an effect of nitrate on an oxygen diffusionresistance located in the nodule cortex. Unlike nitrate, measurable quantities of ⁴⁵calcium were transportedvia the xylem into infected and cortical tissues of soybeannodules: it also passed from the soil into the free space ofthe nodule cortex. Key words: Nitrate, legume nodules, calcium     

Nitrogen Utilization in N-limited Barley during Vegetative and Generative Growth: I. GROWTH AND NITRATE UPTAKE KINETICS IN VEGETATIVE CULTURES GROWN AT DIFFERENT RELATIVE ADDITION RATES OF NITRATE-N

Growth and nitrate uptake kinetics in vegetatively growing barley(Hordeum vulgare L., cvs Laevigatum, Golf, and Mette) were investigatedin solution culture under long-term limitations of externalnitrogen availability. Nitrate was fed to the cultures at relativeaddition rates (RA) ranging from 0.02 to 0.2 d^–1. Therelative growth rate (RG, calculated for total plant dry weight)correlated well with RA in the range 0.02 to 0.07 d^–1.In the RA range from 0.07 to 0.2 d^–1 RG continued to increase,but an increasing fraction of nitrogen, added and absorbed,was apparently stored rather than used for structural growth.The RG of the roots was less affected by RA. V_max, for net nitrateuptake increased with RA up to 0.11 d^–1, but decreasedat higher RA. The decline in V_max coincided with a build-upof nitrate stores in both roots and shoots. V_max, expressedper unit nitrogen in the plants (the relative V_max, was higherthan required for maintenance of growth (up to 30-fold) at lowRA, whereas at higher RA the relative V_max decreased. Kineticpredictions of steady-state external nitrate concentrationsduring N-limited growth ranged from 0.2 to 5.0 mmol m^–3over the RG range 0.02 to 0.11 d_–1. It is suggested thatthe nitrate uptake system is not under specific regulation atlow RA, but co-ordinated with root protein synthesis and growthin general. At RA higher than 0.11 d_–1, however, specificregulation of nitrate uptake, possibly via root nitrate pools,become important. The three cultivars showed very similar growthand nitrate uptake characteristics. Key words: Barley, growth, nitrogen limitation, nitrate uptake, kinetics     

EFFECT OF FLUORIDE ON THE RESPIRATION OF LEAVES FROM HIGHER PLANTS

The effect of fluoride on the respiration of leaves from Chenopodiummurale and soybean [Glycine max, Merr., Hawkeye variety) wasstudied. Fluoride treatment included both excised leaves culturedin nutrient solutions and leaves from plants fumigated withHP atmosphere. Tissues treated with low fluoride concentrationswhich initially showed increased oxygen uptake eventually showeddecreased oxygen consumption. Tissues treated with a high concentrationof fluoride showed an increased oxygen uptake if analyzed soonafter treatment initiation. Increase in respiration generallytook place before visible damage was manifested. Decrease inrespiration was correlated with pronounced injury of tissues.Besides concentration of fluoride and the time lapse of treatment,the pH of the culture solution in which fluoride was supplemented,tissue age, and plant species, were important factors affectingrespiration. The effect of 2, 4-dinitrophenol (DNP) on respirationwas very similar to that of fluoride in that the effect differedwith pH, concentrations, time of treatment, leaf age, and plantspecies. The respiration of fluoride treated leaves was stimulatedless by DNP than that of control leaves. (Received July 18, 1967; )     

Whole Plant Studies using Radioactive 13-Nitrogen: II. A COMPARTMENTAL MODEL FOR THE UPTAKE AND TRANSPORT OF NITRATE IONS BY Zea mays

Nitrate ion uptake by the roots of hydroponically grown maizeseedlings was measured using the short-lived isotope ¹³N. Itis shown to be described by a four compartment model, recognizablynitrogen in the root bathing solution, nitrogen which is readilyexchangeable from the root, nitrogen bound in the root, andnitrogen transported from the root. Some of the absorbed activity leaks back into the root bathingsolution with the efflux from the root, as a fraction of theinflux, increasing with concentration to be greater than 0–8at external nitrate ion concentrations above about 1.0 mol m^–3.The capacity of the exchangeable root pool increases with externalnitrate ion concentration, approaching the expected cytoplasmicnitrate ion content at the highest external nitrate ion concentrationsstudied (70 mol m^–3). The investigation has highlighted the problems of interpretinguptake profiles in experiments for which the 10 min half-lifeof ¹³N dictates experimental times that are comparable withthe times for saturation of root pools. Key words: Zea mays, ¹³N, Compartmental model, Nitrate uptake     

Integrated Control of Nitrate Uptake by Crop Growth Rate and Soil Nitrate Availability under Field Conditions

There is still disagreement about whether crop growth rate orsoil nitrate concentration control nitrogen absorption by cropsunder field conditions. The influence of these factors on thecontrol of N uptake rate was examined in the absence of waterstress, using data on dry matter production, above-ground nitrogenaccumulation and soil nitrate concentration from several N-fertilizerexperiments on winter wheat, winter oilseed rape and maize.The results confirmed that crops can accumulate nitrogen farin excess of the ‘critical dilution curve’, whichdefines the minimum amount of nitrogen needed for maximal growthrate: the N concentration in plants could exceed the criticalN concentration by 70 to 80% for the three species studied.The nitrate uptake rate index (NUI) was calculated as the ratioof actual and critical N uptake rates, at intervals of 1 week.NUI varied with nitrate concentration in the 0–30 cm soillayer according to a Michaelis–Menten equation (with oneor two components). This response was compared with the kineticsof saturation of the nitrate uptake systems: the high affinitytransport system (HATS) and the low affinity transport system(LATS). As a result, it is proposed that there is a criticalN dilution curve delimiting two domains of N use by plants.This is linked to the two nitrate transport systems, with HATSworking at low nitrate concentrations, below the critical dilutioncurve, and LATS at high nitrate concentrations, above the curve.NUI provides another method for calculating the actual nitrateuptake rate, which depends on the maximal crop growth rate (withoutN deficiency) and on the external nitrate concentration. Copyright2000 Annals of Botany Company Nitrate, uptake rate, growth rate, wheat, maize, oilseed rape, soil N availability