Supply and uptake of potassium,calcium and magnesium of spray carnations (Dianthus caryophyllus) grown in rockwool

Summary In two experiments with carnations grown in rockwool the effects of different cation ratios in the nutrient solution were studied. The results showed that carnations need a high calcium supply. The crop did not appear to be sensitive to different potassium-magnesium ratios in the nutrient solution. In the nutrient solution added mole ratios K∶Ca∶Mg=55∶35∶10 seemed to be optimal. Such ratios in addition led to ratios of 55∶30∶15 in the root environment. Tissue analysis showed that in younger leaves of peduncles harvested a potassium content of 900 mmol per kg dry matter was optimal. For calcium a content of 350 and for magnesium 100–150 mmol per kg was needed. Analytical data of plant-sap analyses were closely correlated with data gained by digestion of dried material. For potassium and magnesium the relationships were linear. However, for calcium a curvilinear relationship was found. In the experiments indications were obtained that a sufficient calcium supply suppressed foot rot in carnations.     

Effect of vacuum drying on protein-mannitol interactions: The physical state of mannitol and protein structure in the dried state

The purpose of the present studies was to systematically investigate protein-mannitol interactions using vacuum drying, to obtain a better understanding of the effect of protein/mannitol wt/wt ratios on the physical state of mannitol and protein secondary structure in the dried state. Solutions containing β-lactoglobulin (βLg):mannitol (1∶1–1∶15 wt/wt) were vacuum dried at 5°C under 3000 mTorr of pressure. The physical state of mannitol was studied using x-ray powder physical state of mannitol was studied using x-ray powder diffractometry (XRPD), polarized light microscopy (PLM), Fourier-transform infrared (FTIR) spectroscopy, and modulated differential scanning calorimetry (MDSC). XRPD studies indicated that mannitol remained amorphous up to 1∶5 wt/wt βLg:mannitol ratio, whereas PLM showed the presence of crystals of mannitol in all dried samples except for the 1∶1 wt/wt βLg:mannitol dried sample. FITR studies indicated that a small proportion of crystalline mannitol was present along with the amorphous mannitol in dried samples at lower (less than 1∶5 wt/wt) βLg:mannitol ratios. The T_g of the dried 1∶1 wt/wt βLg:mannitol sample was observed at 33.4°C in MDSC studies, which indicated that at least a part of mannitol co-existed with protein in a single amorphous phase. Evaluation of the crystallization exotherms indicated that irrespective of the βLg:protein wt/wt ratio in the initial sample, the protein to amorphous mannitol ratio was below 1∶1 wt/wt in all dried samples. Second-derivative FTTR studies on dried βLg and recombinant human interferon α-2a samples showed that mannitol affected protein secondary structure to a varying degree depending on the overall mannitol content in the dried sample and the type of protein.     

Comparison of methods of expression and measurement of cation exchange capacity of plant roots

Summary Cation exchange capacity (CEC) of roots of fifteen genetically different tea clones was measured and the values were expressed on surface area and weight basis. The precision of the two methods is almost identical. The weight basis is, however, preferred as it is more convenient and less time consuming.In another experiment. CEC was determined separately on whole root system and on fractionated root segments (i.e. white and brown root portions). Highly significant and positive relationship between CEC values obtained with whole roots and those calculated from the fractionated root segments indicates that CEC can be more successfully measured on whole roots without sacrificing accuracy. Practical implications of both the procedures in root CEC-nutrient uptake relationship study was discussed.     

Control of the take-all fungus byMicrodochium bolleyi,and interactions involvingM. bolleyi,Phialophora graminicola andPericonia macrospinosa on cereal roots

Summary In glasshouse experiments,Microdochium bolleyi (Mb) significantly reduced infection of wheat roots by the take-all fungus,Gaeumannomyces graminis vartritici (Ggt), when inocula were dispersed in soil at ratios of 10∶1 (Mb:Ggt) or more. Spread of take-all lesions up roots from a layer of inoculum also was reduced when Mb was inoculated immediately below the crown. In contrast,Periconia macrospinosa did not control take-all even at an inoculum ratio of 100∶1. M. bolleyi interfered with growth on roots byPhialophora graminicola, a known biocontrol agent of take-all. It is suggested that this phenomenon and control of take-all by these fungi occur by competition for cortical cells that senesce in the normal course of root development.     

Tissue culture of goldenseal (Hydrastis canadensis L.)

Summary Goldenseal (Hydrastis canadensis L.), a popular native American medicinal plant, is currently listed as endangered or threatened in over one-third of the states in which it is listed. The objective of this study was to develop an in vitro culture protocol for Goldenseal. Excise embryos were grown on Gamborg's B-5 medium with 0,1 or 10 μM gibberellic acid (GA₃), and supplemented with 30 gl⁻¹ sucrose and 8 gl⁻¹ agar. Germinated embryos provided explants (leaf and root tissue) that were subsequently cultured on various media with combinations of naphthleneacetic acid (NAA) and benzyladenine (BA). All NAA/BA combinations produced multiple shoots, roots, and callus. Leaf explants cultured on medium with 1∶10 μM NAA:BA and root explants on medium with 1∶1 μM NAA:BA could be successfully used for mieropropagation.     

Changes in variable charge and acidity of rye (<Emphasis Type="Italic">Secale cereale</Emphasis> L<Emphasis Type="Italic">.</Emphasis>) roots surface under Zn-stress

The plants of winter rye variety Rostockie grown in nutrient solution prepared according to Marschner and Romheld (1983) were stressed at shooting stage with different zinc (ZnCl₂) concentrations of 0, 20, 200 and 400 mgXdm⁻³ during 10 days at pH = 4.5. The control plants were grown continuously at pH = 7, without Zn²⁺. The roots of all plants were titrated with 0.1 molXdm⁻³ NaOH in 1 molXdm⁻³ NaCl solution with a rate 0.01 ml/min using auto-titrator Titrino 702 (Metrohm). The amount of the base consumed between pH 3 and 10 was recorded with a step of 0.1 pH unit. From the titration data root surface charge was characterized. Roots grown at pH = 4.5 without Zn²⁺ addition, had apparently the same charge properties as the control roots. Under 200 and 400 mgXdm⁻³ of zinc addition, variable charge, Q, and the cation exchange capacity, CEC, of the roots significantly decreased as did the fractions of surface acidic functional groups of strong and medium acidity i.e. the groups having apparent surface dissociation constants, Kapp, between 10^−3.5 and 10^−5.5. For 20 mgXdm⁻³ zinc stress the fraction of weaker surface groups (surface dissociation constants around 10^−6.5) decreased also. The surface charge density, SCD, of roots decreased under the Zn stress.     

Physicochemical selectivity for cations and CEC of grass roots

Summary A study of root selective adsorption of Ca, Mg, K and Na was made with rootlets of 20 species of Gramineae (from natural vegetation) exhibiting low cation exchange capacities (CEC) scattered over a narrow range 7.6–16.7 meq 100 g^-1 dry matter). For each sample of rootlets successive measurements were made of its CEC (amount of Ca adsorbed from 0.05 N calcium nitrate solution) and the amounts of Ca, Mg, K and Na adsorbed from a tetracationic nitrate solution having equal concentrations (0.05 N) of each cation. Rootlet selectivity for bivalent cations increased with CEC and was greater for Ca than for Mg. In contrast, the selectivity for monovalent cations increased with decreasing CEC and was greater for K than for Na. A root's selective adsorption may therefore be governed by its CEC, in conformation with the exchange laws, as is the case with clays and resins. Paper read at the XII International Botanical Congress (mineral nutrition session) held in Leningrad, July, 1975.     

Biomass, morphology and nutrient contents of fine roots in four Norway spruce stands

Fine root systems may respond to soil chemical conditions, but contrasting results have been obtained from field studies in non-manipulated forests with distinct soil chemical properties. We investigated biomass, necromass, live/dead ratios, morphology and nutrient concentrations of fine roots (<2 mm) in four mature Norway spruce (Picea abies [L.] Karst.) stands of south-east Germany, encompassing variations in soil chemical properties and climate. All stands were established on acidic soils (pH (CaCl₂) range 2.8–3.8 in the humus layer), two of the four stands had molar ratios in soil solution below 1 and one of the four stands had received a liming treatment 22 years before the study. Soil cores down to 40 cm mineral soil depth were taken in autumn and separated into four fractions: humus layer, 0–10 cm, 10–20 cm and 20–40 cm. We found no indications of negative effects of N availability on fine root properties despite large variations in inorganic N seepage fluxes (4–34 kg N ha⁻¹ yr⁻¹), suggesting that the variation in N deposition between 17 and 26 kg N ha⁻¹ yr⁻¹ does not affect the fine root system of Norway spruce. Fine root biomass was largest in the humus layer and increased with the amount of organic matter stored in the humus layer, indicating that the vertical pattern of fine roots is largely affected by the thickness of this horizon. Only two stands showed significant differences in fine root biomass of the mineral soil which can be explained by differences in soil chemical conditions. The stand with the lowest total biomass had the lowest Ca/Al ratio of 0.1 in seepage, however, Al, Ca, Mg and K concentrations of fine roots were not different among the stands. The Ca/Al ratio in seepage might be a less reliable stress parameter because another stand also had Ca/Al ratios in seepage far below the critical value of 1.0 without any signs of fine root damages. Large differences in the live/dead ratio were positively correlated with the Mn concentration of live fine roots from the mineral soil. This relationship was attributed to faster decay of dead fine roots because Mn is known as an essential element of lignin degrading enzymes. It is questionable if the live/dead ratio can be used as a vitality parameter of fine roots since both longevity of fine roots and decay of root litter may affect this parameter. Morphological properties were different in the humus layer of one stand that was limed in 1983, indicating that a single lime dose of 3–4 Mg ha⁻¹ has a long-lasting effect on fine root architecture of Norway spruce. Almost no differences were found in morphological properties in the mineral soil among the stands, but vertical patterns were apparently different. Two stands with high base saturation in the subsoil showed a vertical decrease in specific root length and specific root tip density whereas the other two stands showed an opposite pattern or no effect. Our results suggest that proliferation of fine roots increased with decreasing base saturation in the subsoil of Norway spruce stands.     

The influence of soil chemistry on fine root aluminum concentrations and root dynamics in a subalpine Spodosol,Washington State,USA

The relationship between root Al concentrations and Al fractions in the soil solution was examined in a mature Abies amabilis ecosystem in the Cascade Range of Washington State. The naturally acidic soils in these ecosystems lead to high concentrations of aqueous Al in soil solutions and contribute to the biocycling of Al by the A. amabilis/T. mertensiana stand. Root concentrations of Al were very closely related to aqueous Al³⁺ activities, but poorly correlated with total aqueous Al concentrations. The solution Al/Ca molar ratios followed a seasonal cycle with low values during the fall and high values during the spring. Ratios remained <1 throughout the year in the Oa horizon while they varied between 2 and 14 in the E and Bhs horizons. The vertical distribution of roots and the mortality of fine roots may be linked to the soil solution Al/Ca ratio. Root cation exchange capacity ranged between 180 and 225 mol g^-1 and the exchangeable Al fraction represented from 12–17% of the total Al content in the root. Evidence for solid-phase co-precipitates of Al with PO₄ and oxalate was indicated from selective dissolution of the root tissue. Sufficient quantities of PO₄ and oxalate exist in the roots to tie up 20–40% of the Al present in the roots of the Oa and E horizons, but only 9% of that present in the Bhs horizon. Species differences in the distribution of Al between the above-ground and below-ground components may be dictated by these retention processes in the fine roots.     

Effects of dietary lead,fish oil,and ethoxyquin on hepatic fatty acid composition in chicks

Three experiments were conducted with day-old broiler chicks reared to 18 or 19 d of age. The objective was to examine the effects of dietary oil (cottonseed oil vs fish oil), dietary antioxidant (0 vs 75 ppm ethoxyquin), and dietary lead (0 vs 1000 ppm Pb as lead acetate trihydrate) on hepatic fatty acid composition. A 2×2 factorial arrangement was used in all experiments. In Experiment 1, the factors were oil (4% of each) and Pb. In Experiments 2 and 3, the factors were ethoxyquin and Pb in diets containing 3.5% cottonseed oil (Experiment 2) or 3.5% fish oil (Experiment 3). Hepatic fatty acid profiles were measured by gas-liquid chromatography in 10 chicks/treatment (Experiment 1) or 4 chicks/treatment (Experiments 2 and 3). Dietary oils altered the profiles, with cottonseed oil producing the higher values for linoleic acid (18∶2) and arachidonic acid (20∶4). With fish oil, in addition to the lower levels of 18∶2 and 20∶4, there were significant levels of eicosapentaenoic acid (20∶5) and docosahexaenoic acid (22∶6). Pb enhanced the levels of 20∶4, but the effect was greater with cottonseed oil diets compared with fish oil diets. The enhanced 20∶4 levels resulted in lower ratios of 18∶2/20∶4. Ethoxyquin enhanced the level of 18∶2 with the cottonseed oil diet, and of 20∶5 and 22∶6 with the fish oil diet. Ethoxyquin decreased the level of hepatic 20∶4 when fish oil was fed. The results clearly show that all three factors (oil type, Pb level, and ethoxyquin level) after hepatic fatty acid composition. Both oil source and Pb level appeared to exert an effect on the metabolic conversion of 18∶2 and 20∶4. The primary effect of ethoxyquin was to enhance the levels of polyunsaturated fatty acids in liver. The data do not allow the partitioning of possible ethoxyquin effects to protection of polyunsaturated acids in feed vs protection of polyunsaturated acids in liver tissue. Use of trade names implies neither approval by the North Carolina Agricultural Research Service of products named nor criticism of products not named.     

Root Zone Temperature Effects on Growth and Nitrate Absorption in Rape (Brassica napus cv. Emerald)

Effects of root temperatures, ranging from 10–35 °C, on growth and nitrate inflow of fodder rape seedlings (cv.Emerald) were examined. These were cultured in solution, withtheir shoots held at 25 ° C. Nitrate inflow (uptake rateper unit root length) was little affected over the temperaturerange 10–30 ° C, although enhanced values were foundat 35 ° C. Nitrate absorption by roots at 10-30 ° Cdepleted solution concentrations to an apparent minimum of approximately6.0 µM NO₃^–. Relative growth rates were highestwith root temperatures of 25 ° C and 30 °C, and thesewere associated with the greatest nitrate depletion rates fromsolution. Root: shoot weight ratios were also greatest at 25°C and 30 °C. At 10 °C and 35 °C a relativelylarge shoot on a small root maintained nitrate inflow in spiteof the plants' slow growth rate. The nitrogen concentrationin the shoots was little affected by root temperature. Slowgrowth at a root temperature of 10 °C was not associatedwith a shortage of nitrogen in the shoots. The principal influenceof temperature appears to be on extension and differentiationof root tissues, possibly through effects on carbohydrate supplyto root meristems.     

Effect of metabolites ofAspergillus niger andTrichoderma viride on development and structure of radicle of cocoa (Theobroma cacao) seedlings

Both the volume and concentration of filtrate ofAspergillus niger andTrichoderma viride influenced the development of the radicles of cocoa seedlings. Radicles placed in Petri dishes containing filter paper moistened with 20 and 30 ml of undiluted filtrate and filtrate dilutions of 1∶1 and 1∶2 failed to develop lateral roots and eventually died. The culture filtrate ofA. niger was more repressive. Radicles in the same volume of filtrate (20 and 30 ml) of higher dilutions (1∶5 and 1∶10) developed lateral roots and survived. Radicles placed in less volume (≤10 ml) survived and produced lateral roots irrespective of concentration of filtrates. Development of the radicles and roots in the control was consistently better (P=0.05) than in filtrate solutions of eitherA. niger orT. viride. The hypocotyls of seedlings under the influence of metabolites ofA niger showed greater cambial activity and formed xylem vessels and tracheids with larger lumina.     

Effect of Temperature on the Radial Exchange of Labelled Water in Maize Roots

The temperature dependence of the efflux kinetics of labelledwater in isolated maize roots has been studied. The purposeof these experiments was to obtain the energy of activation,E (kcal/mole), of the rate-limiting step in this radial exchangeprocess under various experimental conditions. Estimates ofE were obtained from linear relations between ln{D'_w} and thereciprocal of the absolute temperature; values of the apparentdiffusion coefficient, D'_w, of labelled water in the root werefound from an analytical treatment of the efflux data in termsof a cylindrical diffusion model. The energy of activation forlabelled-water exchange in normal roots was 14.9 kcal/mole.The corresponding value for ‘dead’ (boiled) rootswas 3.9 kcal/mole. These values of E substantiate the view thatin normal roots the penetration of water across the membranesof the root cells constitutes the rate-determining step in theefflux whereas in ‘dead’ roots extracellular diffusionof water is the source of rate-control. Similar temperature dependence studies were performed on theefflux kinetics from normal and ‘dead’ roots treatedwith 10^–5 M phenylmercuric acetate (PMA). The energiesof activation for labelled-water exchange in normal and ‘dead’roots under these conditions were respectively 15.5 and 5.3kcal/mole. Moreover, the results of the efflux experiments onPMA-treated roots were considered to indicate that this inhibitorproduces an alteration in some structural aspect of the rate-controlling‘membranes’.     

Root growth,macro-nutrient uptake dynamics and soil fertility requirements of a high-yielding winter oilseed rape crop

Shoot growth, root growth and macro-nutrient uptake by a high-yielding (5t/ha grain) winter oilseed rape crop have been measured. Maximum rooting density in the top 20cm of soil was 9.4 cm cm⁻³ and roots reached a depth of at least 1.8 m. Maximum nutrient uptakes were 364 kg ha⁻¹ for N, 43 kg ha⁻¹ for P, 308 kg ha⁻¹ for K, 287 kg ha⁻¹ for Ca and 16 kg ha⁻¹ for Mg. A 30-day drought coincided with the flowering period and root and shoot growth, as well as nutrient uptake rates, were reduced. Nutrient concentrations in the soil solution necessary to sustain the nutrient fluxes into the root system by diffusive supply have been calculated. Peak values were in the range 10 μM for P to 87 μM for N, lower than the observed concentrations, and it was concluded that nutrient transport to roots was not a limitation to uptake by this rape crop.     

High yellow pigments production by root culture of <Emphasis Type="Italic">Carthamus tinctorius</Emphasis> and its release in medium under gas oil treatment

In this study, the ability of safflower-isolated root cultures to produce yellow pigments was tested. Initially, the growth of isolated roots in static liquid medium was evaluated with different volumes of culture medium. A volume of 6 ml of medium per flask of 250 ml gave the best growth performance and, in this condition of culture, production of pigments from isolated roots treated or not by light has been determined by spectrophotometry (321 and 400 nm). Under these conditions, the production of yellow pigments amounted to 13.18 mg g⁻¹ fresh weight and the light stimulated the synthesis of these pigments by isolated roots. Total yellow pigments of 24.12, 38.91 and 46.38 mg g⁻¹ fresh weight was produced by the roots treated with 9, 13.5 and 18% (v/v) gas oil, respectively, representing high values of production. The pigments were released in large quantities in the medium. The increased synthesis of pigments as a result of gas oil treatment was accompanied by a reduction of the peroxidase activity of roots. Given the high production of yellow pigments, systems of isolated root culture could be considered for the study of a larger scale production of safflower pigments widely used for various industrial purposes.     

The Effect of Copper Toxicity on the Growth and Root Morphology of Rhodes Grass (Chloris gayana Knuth.) in Resin Buffered Solution Culture

A solution culture experiment was conducted to examine the effect of Cu toxicity on Rhodes grass (Chloris gayana Knuth.), a pasture species used in mine-site rehabilitation. The experiment used dilute, solution culture to achieve external nutrient concentrations, which were representative of the soil solution, and an ion exchange resin to maintain stable concentrations of Cu in solution. Copper toxicity was damaging to plant roots, with symptoms ranging from disruption of the root cuticle and reduced root hair proliferation, to severe deformation of root structure. A reduction in root growth was observed at an external Cu concentration of < 1 μM, with damage evident from an external concentration of 0.2 μM. Critical to the success of this experiment, in quantitatively examining the relationship between external Cu concentration and plant response, was the use of ion exchange resin to buffer the concentration of Cu in solution. After some initial difficulty with pH control, stable concentrations of Cu in solution were maintained for the major period of plant growth. The development of this technique will facilitate future investigations of the effect of heavy metals on plants.     

Root Aeration and Respiration in Young Mangrove Plants (Avicennia marina (Forsk.) Vierh.)

The roots of young plants of Avicennia marina (Forsk.) Vierh.grown under simulated tidal conditions were harvested so asto obtain the entire root system. The roots were subdividedand weighed and subsamples taken for manometric determinationof respiration rates at different temperatures. The supply capacityof the above-ground portion of the root system was determinedand the results compared in terms of supply and demand. Theoxygen consumption rate of the roots at 15°C was found tobe 1·69±0·07 µmol kg^–1 s^–1for cable roots and 3·27±0·12 µmolkg^–1 s^–1 for fine roots. The Q₁₀ for respirationwas 2·55 for oxygen consumption in both fine and cableroots, and for carbon dioxide production was 2·66 forfine roots and 3·04 for cable roots. The respiratoryquotient varied with temperature but was less than unity. Concentrationdifferences of between 1·8 mol m^–3 and 3·4mol m^–3 between the inside of root and the air were sufficientto permit aeration of the root system by diffusion alone, andthe aerenchyma contained sufficient oxygen to maintain aerobicconditions while the roots were covered with water. The effectof tide and seasonal temperature change on gas exchange, togetherwith the possibility of some form of carbon dioxide fixationwithin the root, are examined and the implications of theseeffects on growth and development are discussed. Key words: Mangrove, root aeration, respiration, aerenchyma     

Aluminum uptake and aluminum-induced rapid root growth inhibition of rice seedlings

Aluminum (Al) inhibits root growth in acidic soil, but the site of action of Al remains unclear. We investigated whether the rate of Al accumulation correlates to Al-indeced rapid root growth inhibition in rice seedlings (Oryza sativa L. cv. Youngnam). Growth of roots was significantly inhibited by 100 μM AICI₃, as early as 1 h after the treatment. The inhibition of root growth was strongly dependent on Al concentration (l₅₀ = 20 (μM) and Al-exposure time (l₅₀ = 23 min at 25 μM Al) in a solution of 10 mM KCI and 1 mM CaCl₂ buffered by 10 mM Mes/KOH (pH 4.5). Using ICPES, massive uptake of Al by roots was observed even at 15 min treatment of 25 μM Al. The kinetics of Al uptake by the roots closely corresponded to the inhibitory effects of Al on root growth. When the roots of seedlings were exposed to 50 (μM Al for 1 h, then sectioned and stained with hematoxylin, all cell types of the roots showed the presence of Al in the cytoplasm. These results indicate that Al was rapidly taken up into the root cells and thereby reduced root growth.     

The kinetics of calcium and magnesium entry into mycorrhizal spruce roots

 The entry of calcium and magnesium from external sources into mycorrhizal roots of 3-year-old Norway spruce trees (Piceaabies [L.] Karst.) was monitored. Roots of intact plants were exposed for various periods of time, ranging from 2 min to 48 h, to nutrient solutions which contained the stable-isotope tracers ²⁵Mg and ⁴⁴Ca. After labelling, samples of roots were excised from the plants, shock-frozen, cryosubstituted and embedded. The resulting isotope composition in this material was analysed by a laser-microprobe-mass-analyser (LAMMA) at relevant positions within cross-sections of the roots. For both elements, we determined (i) the fractions of the isotopes originating from the plant prior to labelling, and (ii) the fraction of isotopes originating from the corresponding tracer that penetrated into the root. Both divalent cations rapidly penetrated across the cortical apoplast and reached the endodermis. After 2 min of exposure to the labelling solution, an initial transient gradient of the tracers could be observed within the root cortex. Subsequently, calcium as well as magnesium equilibrated between the apoplast of the entire cortex and the external tracer with a half-time, t_1/2, of about 3 min. In contrast, the kinetics of radial movement into the vascular stele showed a delay with a t_1/2 of 100–120 min. We take this as strong evidence that there exists a free apoplastic path for divalent cations in the cortex and that the endodermis is a major barrier to the further passage of Mg and Ca into the xylem. While ²⁵Mg in the labelling solution exchanged rapidly with Mg in the cortical apoplast, the exchange across the plasma membrane with Mg present in the protoplasm of the same cortical cells was almost 2 orders of magnitude slower. The kinetics of Ca and Mg entry at +6 °C were similar to those obtained at a root temperature of +22 °C. Received: 23 December 1998 / Accepted: 17 September 1999