Aerated Nutrient Solution Research Articles

Kinematic Analysis using a Novel Method of Marking Roots with the Fluorescent Dye Calcofluor

Kinematic analysis allows accurate description of physiological changes along root axes by additionally taking into account changes due to dilution as cells expand. In previous studies using kinematic analysis, roots have been marked with ink by fine-tipped pens or single hair brushes. These methods have occasionally reduced root growth and limited resolution to the width of the marks, usually 1 mm. We describe a new method of marking roots with the fluorescent dye calcofluor which does not reduce root growth. The terminal 7 mm of bean root tips were grown vertically in a glass chamber into which a constant flow of aerated nutrient solution was passed. A 0.001% calcofluor solution was pulsed through the chamber for 1 min. Excess calcofluor was removed rapidly by a high rate of nutrient flow (200 ml·h–1) for 3 min. after which flow was reduced to 20 ml/hr. Roots were magnified 11.5× under a microscope mounted horizontally and five digitized images captured every 5 min. Imaging software allowed determination of fluorescence of individual pixels along the length of the root. Fluorescence decreased in the zone of cell elongation due to dilution as cells expanded. This method may improve resolution of kinematic analysis to the length of individual pixels, which was 18 microns at 11.5× magnification.

Content of water soluble carbohydrates under oxygen deprivation in plants with different flooding tolerance

We investigated the carbohydrate concentration of plant species naturally growing in habitats with a high risk of oxygen shortage (Senecio aquaticus Hill,Myosotis palustris (L.) L. em.Rchb) and congeneric species from drier sites (Senecio jacobaea L.,Myosotis arvensis (L.)Hill) Plants from the four species were cultivated in either nitrogen-flushed or aerated nutrient solution. Following oxygen shortage in the root environment a two—fourfold increase of carbohydrate content was found in the roots as well as in the shoots of the species examined. Although, the tendency in the response of both genera to the hypoxic conditions in the nutrient solution was the same, there were differences in concentration and composition of the water soluble carbohydrates. The flooding tolerantSenecio aquaticus accumulated the highest amounts of carbohydrates, in particular fructans (nearly 60% of the soluble carbohydrates, compared with 30% under aerated conditions). The increasing amount of sugars found under hypoxia-inducing conditions proved that substrate availability was not the limiting factor for survival under wetland conditions.

Phytotoxic effects of the high molecular weight fraction of an aqueous leaf litter extract on barley root development

The root development of barley seedlings grown for one week in an aerated nutrient solution was studied in the presence of dissolved organic matter from an aqueous chestnut leaf litter extract. In particular, the different effects of low and high molecular weight fractions (small molecules: molecular weight <1000; large molecules: >10,000) of the leaf litter extract were examined. In the presence of large molecules root growth was inhibited, an irregular root tip morphology was observed, and Ca and Mg concentrations in the shoots were lower than in control plants. These phytotoxic effects were not caused by the formation of an impermeable layer of large molecules on the root surfaces that lower accessibility for nutrient cations as inferred from voltammetric experiments. A germination assay using spruce seeds, however, indicated allelochemical effects of large molecules, which exhibit a higher aromaticity than the small molecules as indicated by spectroscopic characterisation. In the growth experiments with small molecules, no influence on the root development of barley was evident, but an increase of Ca and Mg in the shoots was detected. During these growth experiments, a large amount of the small molecules, mainly simple phenols and amino acids, disappeared from the nutrient solution. The loss of small molecules was most likely the effect of mineralisation.

Susceptibility of low chill peach rootstocks to Phytophthora spp

Peach seedlings (Prunus persica L. Batsch cv. Ansbacher, Boyles, Clarke's Shanghai, Neilson (Fred Hill), Okinawa, O'Meara, Richens Nos 1,2 and 3, Tomm's Early and Tomm's Shanghai), which are commonly used as rootstocks for low chill peaches in coastal New South Wales, were all susceptible to Phytophthora cinnamomi and P. cambivora and to a lesser extent P. parasitica, P. citricola, P. cryptogea, and P. megasperma, when tested by stem inoculations in the glasshouse. Myrobalan H29C plum (P. cerasifera Ehrh.) cuttings showed more resistance than peach seedlings. Variety of seedling peach was highly significant in stem inoculation experiments, but the performance of each varied between experiments. Root inoculations in aerated nutrient solution showed all rootstocks were susceptible to P. cinnamomi, but Neilson (Fred Hill) peach was more tolerant than other seedling peaches and less tolerant than Myrobalan H29C plum. No recommendation could be made on a rootstock for low chill peaches more tolerant of root and collar rots and waterlogging.

Growth, water transport and transpiration in root-restricted plants of bean, and their relation to abscisic acid accumulation

The effects of root zone confinement on growth, water transport and transpiration, and their association with abscisic acid (ABA) accumulation in Phaseolus vulgaris L., were studied. Transfer of 6-day-old seedlings, at time zero (TZ), to aerated nutrient solutions, in 10-ml and non-restricting-volume containers, divided the plants for treatment as restricted root-zone plants (RRPs) and non-restricted root-zone plants (NRPs). Growth restraint in the RRPs was not detectable 2 days after TZ, but was very pronounced after a further 8 days. Analysis of ABA was carried out 2 and 12 days after TZ. In the earlier analysis, a much higher level of ABA was detected in the leaves and the roots of the RRPs than in those of the NRPs, preceeding any expression of growth suppression; in the later analysis, the concentrations of ABA in the leaves and the stems of the RRPs were much greater than in those of the NRPs, while in the roots, the previous difference had disappeared. Water transport from the roots, expressed for the whole root system and per unit weight of root biomass, was much lower in both intact and detopped RRPs, than in NRPs. The reduced transport of water from the RRP roots was pronounced 12 days after TZ, in spite of the disappearance of the formerly detected difference between the two treatments in root-accumulated ABA. The transpiration rate per unit leaf area was similar in both treatments, irrespective of the higher level of ABA in the foliage of the RRPs. The leaf water potentials of RRPs and NRPs, as measured 12 days after TZ were also similar. The root-exuded ABA, as measured 12 days after TZ reached values of 0.13 and 0.25 ng ABA/g fresh wt. root/h, in the RRPs and NRPs, respectively. It was, therefore, concluded that the higher level of ABA in the RRP leaves was not a consequence of an enhanced transport from the restricted roots. The present work led to the conclusion that root-zone restriction might promote ABA accumulation in the root and the shoot. The possible influence of such accumulation on other processes in RRPs, such as growth suppression, water transport and transpiration, is in question.

Water uptake regulation in peach trees with split‐root systems

ABSTRACTThe water uptake of 3‐ to 4‐year‐old peach trees ‘May‐crest/Prunus Damas’ grown in an aerated nutrient solution was studied using a split‐root system. Each container and the whole tree were weighed independently to measure water absorption by both parts of the root system and tree transpiration. Water potential of leaves was measured with a pressure chamber. Water potential of roots was estimated using root suckers sealed in plastic bags before the measurement. The nutrient solution was removed from one container so that half the root system was left in humid air for 48 h. Water potential of roots left in solution decreased, which (partly) maintained water absorption and thus transpiration. No modification of root hydraulic resistance was required to simulate the experimental results. Nevertheless, enhancement of absorption by the roots supplied with solution cannot compensate for the water loss by transpiration. Depletion of water from the plant essentially came from the non‐absorbing roots. This was demonstrated by substituting vegetable oil for nutrient solution around one half of the split‐root system, and by following the changes in root volume on the basis of Archimedes principle. Conflicting results in the literature about apparent changes in hydraulic resistance are discussed.

The Diurnal Pattern of Nitrate Uptake and Reduction by Spinach (Spinacia oleracea L.)

Spinach plants were grown in bowls of aerated nutrient solution in a controlled environment chamber for 24 h, and harvested every 3·5-5 h to record their growth, nitrate and water uptake, and plant nitrate concentration. Twelve such experiments are described, either with a 14/10 h dark/light regime, or continuous light or darkness. The irradiance was either 110, 320, or 510 μmol m-2 s-1 (PPFD). All these regimes began at the end of the light period of a 14/10 h dark/light regime (510 μmol m-2 s-1) lasting approximately 2 weeks.Nitrate uptake rate per g of dry weight of plant continued almost unabated at about 17 μmol h-1 through the initial 14-h dark period, and then fell away sharply if the light was not restored, but increased slightly when it was. With continuous light at 510 μmol m-2 s-1, uptake rate rose steadily for the first 24 h of light, and then fell sharply for about 6 h. Shoot nitrate concentration increased about three-fold in the dark phase, and declined in the light at a rate which was positively related to the irradiance. Root nitrate concentration was several times higher than that of the shoot: its diurnal change was smaller (relative to the mean) than that of the shoot. Nitrate reduction occurred to a small extent in the dark, and increased rapidly as soon as the lights came on, to remain at a roughly constant rate (related to the irradiance) throughout the light phase. Dry matter increase in the light was related to irradiance, but with little increase above 320 μmol m-2 s-1. Respiratory weight loss in the dark was not detectable. Rate of fresh weight increase was approximately constant throughout light and dark periods.The results compare quite well with the predictions of a simple simulation model, based on the pump/leak principle.

Hormonal responses to partial drying of the root system ofHelianthus annuus

Plants of Helianthus annuus were pot-grown in soil,with approximately 30% of the root system protruding through the base. After 7 d, the upper part of the root system of half of the plants was exposed to drought (internal roots) while the lower part was kept in aerated nutrient solution (protruding root). The treatment rapidly reduced the internal roots'water content from 26.1 to 21.9 g g -1 dry weight (DW), while in protruding roots of stressed plants it slowly and continuously decreased from 31.9 to 25.2 g g -1 DW. Leaf water content rapidly decreased in treated plants from 7.4 to 6.4 g g -1 DW in the first 2 d and then reached a plateau. In stressed plants leaf stomatal resistance was significantly higher in the first 3 d while leaf water potential was lower only on the last day

Fructan content of wheat seedlings (Triticum aestivum L.) under hypoxia and following re-aeration.

We studied fructan accumulation in wheat seedlings (Triticum aestivum L. cv. Alcedo) caused by oxygen shortage around the root. Plants were cultivated in either nitrogen-flushed or aerated nutrient solution. In response to the nitrogen treatment there was an accumulation of soluble carbohydrates in shoots as well as in roots. The main contribution was due to fructans. The content of fructo-oligosaccharides had been increased five-fold in the roots and seven-fold in the shoots. This is incompatible with the assumption that higher substrate consumption follows enhanced fermentation under oxygen shortage. Re-aeration of the nitrogen-flushed nutrient solution resulted in enhanced consumption of stored carbohydrates, mainly of fructans, accompanied by high growth rates of the roots. The possibility of utilizing fructans quickly if oxygen is available is a possible advantage for plants adapted to hypoxia. Particularly however, it is suggested that the low energy requirements for sucrose: sucrose fructosyl transferase, allowing fructan synthesis even under oxygen shortage, may improve the fitness of plants to survive temporary hypoxia in the rhizosphere.

Effects of Root Zone Restriction on Amino Acid Status and Bean Plant Growth

The possibility that the suppression of shoot growth in restricted root zone plants (RRZP) is caused by a deficiency in N-amino compounds (NAC) in the shoot, possibly due to an insufficient supply from the roots, was studied in bean (Phaseolus vulgaris L.). Root zone restriction to 10 cm3 in an aerated nutrient solution resulted in suppressed plant growth, as compared with control plants grown in a non-limiting root zone volume. Root xylem exudation of solution and N-amino compunds (NAC) following decapitation was much greater in the control, as compared with RRZP, both per plant and per unit root fresh weight (FWT). In both treatments, asparagine comprised more than 52% of the NAC fraction in the root xylem exudate (RE). Its reduced exudation in the RRZP was of a proportion similar to the combined fraction of NAC left over in both treatments. Asparagine accumulation in leaves of the control plants was very high, comprising 73% of the total NAC pool, while in RRZP, it was much smaller and did not exceed 25%. The total NAC amount per unit of leaf FWT was 3·3 times smaller for the RRZP, as compared with the control, resulting mainly from the dramatic drop in asparagine accumulation. In the roots, RRZP accumulated more NAC per unit root FWT than the control. Raising both treatments in distilled water reduced considerably the accumulation of NAC, including asparagine, in their leaves. RRZP was relatively more suppressed by the absence of nutrients than control plants. This phenomenon did occur, despite the fact that NAC and asparagine concentrations in the root and shoot of RRZP were greater than in the control when grown in distilled water; Therefore, it was concluded that root zone restriction might affect the accumulation of NAC and asparagine in the leaves, but that deficiency in these compounds is not the primary or the major cause of growth suppression in RRZP.

Trigo duro: tolerância à toxicidade do alumínio em soluções nutritivas e no solo

Estudou-se o comportamento de 23 linhagens e cultivares de trigo duro (Triticum durum L.), introduzidos do Centro Internacional de Melhoramento de Milho e Trigo (CIMMYT), México, juntamente com um cultivar de triticale e seis de trigo (Triticum aestivum L), em soluções nutritivas contendo seis concentrações de Al3+ (0, 1, 2, 3, 4 e 6 mg/litro), à temperatura constante de 25 ± 1°C, e pH 4,0. A tolerância foi medida pela capacidade de as raízes primárias continuarem a crescer em solução sem alumínio, após 48 horas em solução contendo uma concentração conhecida de alumínio. Todos os germoplasmas de trigo duro estudados e os cultivares de trigo Siete Cerros e Anahuac foram sensíveis à concentração de 1 mg/litro de Al3+. O cultivar de trigo Alondra-S-46 mostrou-se sensível a 4mg/litro de Al3+; o de triticale Chiva e os de trigo BH-1146, IAC-24 e IAC-60 exibiram tolerância à presença de 6 mg/litro de Al3+ nas soluções. Os mesmos genótipos foram também estudados em experimentos em solo ácido (V% = 14 e H + Al = 8,9 meq/100cm³) e em solo corrigido (V% = 65 e H + AI = 2,9 meq/100cm³). As produções de trigo duro em solo ácido foram baixas, variando de 939 a 2.243 kg/ha, comparadas com as dos cultivares de trigo e triticale tolerantes ao Al3+, as quais variaram de 3.584 a 4.922 kg/ha. No experimento em solo corrigido, a melhor linhagem de trigo duro (Avetoro "S" x Anhinga "S" - Pelicano "S" x D 67.2) produziu 4.128 kg/ha, em comparação com o triticale Chiva, 4547 kg/ha, e o melhor trigo IAC-24, 4.906 kg/ha. Esses resultados confirmaram a necessidade de ser incorporada tolerância ao Al3+ nos genótipos de trigo duro visando a seu cultivo em solos ácidos.

Nitrate reduction in seedlings of carob (Ceratonia siliqua L.)

summaryThe distribution of nitrate reduction in young carob plants (Ceratonia siliquaL. cv. Mulata) was studied. Plants (three months old) were grown in aerated nutrient solutions under greenhouse conditions. Reduction of nitrate was estimated both in the leaves and in the roots by: (a) accumulation of nitritein vitro, (b) accumulation of nitritein vivoand (c) disappearance of nitratein vivo.Disappearance of nitratein vivooffered the closest estimation of the rate of nitrate reduction.Leaves consistently showed rates of nitrate reduction lower than those in roots, regardless of assay method. Lowering root temperature had no marked effect on the distribution of nitrate reductase activity in the plant; increasing nitrate concentration in the shoot, however, markedly increased leaf nitrate reduction. The relatively low level of nitrate reductase in leaves appears to be caused mainly by a limitation of nitrate transport from root to shoot. Nitrate reduction takes place in both the root and the shoot of young carob plants with the shoot accounting for approximately 20% of total nitrate reduction in the plant.

Import of calcium by tomato fruit in relation to the day-night periodicity

The day-night periodicity in calcium (Ca) transport into fruits of tomato ( Lycopersicon esculentum Mill.) was investigated by growing plants with two trusses in aerated nutrient solution labelled with 45Ca for 11 h either during the day or at night. The import of Ca by tomato fruits was favoured at night, although it also occurred during the day, but at a much lower rate. The rates of Ca absorption and translocation from roots to shoots did not differ between the day and the night. Withholding the oxygen supply to roots at night, which is a cause of blossom-end rot of tomato fruits in hydroponics, greatly inhibited both the absorption of Ca from roots to shoots.

Photophysiology of turion germination inSpirodela polyrhiza (L.)Schleiden. The cause of germination inhibition by overcrowding

Red-light-induced (via phytochrome) germination decreased with increasing numbers of turions per germination flask (overcrowding). Three hypotheses concerning the mechanism of this germination inhibition were tested, related to abscisic acid, ethylene, and oxygen deficiency: (i) Although abscisic acid is a powerful inhibitor of turion germination it had to be excluded as a cause, because abscisic acid was not secreted from turions into the nutrient solution, (ii) Ethylene (ethrel) strongly inhibited growth of newly formed sprouts, but germination response itself was not inhibited, (iii) Germination inhibition did not appear if short light pulses were substituted by continuous irradiation. It reappeared in the presence of the photosynthesis inhibitor 3-(3, 4-dichlorophenyl)-l, 1-dimethylurea, but it was not observed in aerated nutrient solutions, or when Petri dishes instead of Erlenmeyer flasks were used. Decreased oxygen concentrations in the nutrient solution were produced by turion respiration. Consequently, anaerobiosis within the nutrient solution caused by turion respiration was the reason for germination inhibition by overcrowding.

Effects of Ca supply and stress on uptake and translocation of Ca in two poinsettia cultivars

Distortion of bracts and leaves of poinsettia ( Euphorbia pulcherimma Willd.) is considered to be a symptom of Ca deficiency. This study was designed to determine whether rates of either Ca uptake or translocation, or responses to interactions between Ca uptake/ translocation and transpirational stress differed between the distortion-susecptible “V-14 Glory” cultivar and the non-susceptible “Annette Hegg Dark Red (AHDR)” cultivar. Ca uptake increased linearly with Ca supply in the aerated nutrient solution in both cultivars, but did not differ between cultivars. Strong transpirational stress applied for 24 hr did not significantly reduce Ca uptake measured 1 and 14 days later in either cultivar. Roots had significantly lower Ca tissue concentrations than shoots in both cultivars, and Ca tissue concentrations tended to be higher in the mid-portion of the shoot than in the basal or apical sections. As no clear differences in Ca uptake or translocation between susceptible and non-susceptible cultivars were observed, we suggest that the Ca deficiencies which produce bract/leaf distortion must be localized and produced by within-leaf or -bract processes. Furthermore, transient though intense transpirational stresses are insufficient to affect subsequent Ca uptake in these cultivars.

Physiological Characterization of a Single-Gene Mutant of Pisum sativum Exhibiting Excess Iron Accumulation

Root systems of mutant (E107) and parental (cv ;Sparkle') Pisum sativum genotypes were studied to determine the basis for excess Fe accumulation in E107. Plants were grown with (+Fe-treated) or without (-Fe-treated) added Fe(III)-N,N'-ethylenebis[2-(2-hydroxyphenyl)glycine] in aerated nutrient solutions. Daily measurements of Fe(III) reduction indicated a four-to seven-fold higher reduction rate in +Fe- or -Fe-treated E107, and -Fe-treated Sparkle, when compared with +Fe-treated Sparkle. An agarose-based staining technique used to localize Fe(III) reduction, revealed Fe(III) reduction over most of the length of the roots (but not at the root apices) in both E107 treatments and -Fe-treated Sparkle. In +Fe-treated Sparkle, Fe(III) reduction was either nonexistent or localized to central regions of the roots. Measurements of short-term Fe influx (with 0.1 millimolar (59)Fe(III)-ethylenediaminetetraacetic acid) was also enhanced (threefold) in +Fe- or -Fe-treated E107 and -Fe-treated Sparkle, relative to +Fe-treated Sparkle. The physiological characteristics of E107 root systems, which are similar to those seen in Fe-deficient Sparkle, have led us to conclude that the mutation causes E107 to act functionally as an Fe-deficient plant, and appears to explain the excess Fe accumulation in E107.

Response of seedlings of soybean, sunflower and sorghum to added mineral nutrients

The capacity of seed of soybean, sunflower and sorghum to sustain early growth was studied by growing seedlings from germination to day 15 at 25�C in growth cabinets in either aerated nutrient solution, aerated deionised water or rolled cotton towelling wetted with deionised water. Growth was markedly better in the nutrient solution and significant differences in growth and in content of nitrogen, phosphorus and potassium were observed 7-11 days after imbibition. By day 15 the dry weights of soybean, sunflower and sorghum seedlings grown in rolled towelling were only 38, 20 and 36%, respectively, of those grown in nutrient solution. Growth in deionised water was very poor and most seedlings were beginning to die by day 15. This was associated with a leakage of potassium from the seedlings to the growing medium, an effect consistent with impaired membrane permeability due to calcium deficiency. The marked effect of added mineral nutrients on the early growth of seedlings indicates that vigour tests which seek to measure the growth potential of a seed batch should be conducted under conditions providing adequate nutrition rather than in inert media. The growth of seedlings in aerated nutrient solution at optimum temperature for about 15 days can be taken as quantitative measures of potential growth and seed vigour. A comparison of growth of seedlings in aerated nutrient solution and an inert medium can be taken as a measure of the nutrient status of a seed lot.

Lipid Composition of Plasma Membranes and Endomembranes Prepared from Roots of Barley (Hordeum vulgare L.)

Membrane fractions enriched in endoplasmic reticulum (ER), tonoplast and Golgi membranes (TG) and plasma membranes (PM) were prepared from barley (Hordeum vulgare L. cv CM 72) roots and the lipid compositions of the three fractions were analyzed and compared. Plants were grown in an aerated nutrient solution with or without 100 millimolar NaCl. Each membrane fraction had a characteristic lipid composition. The mole per cent of the individual phospholipids, glycolipids, and sterols in each fraction was not altered when roots were grown in 100 millimolar NaCl. The ER had the highest percentages of phosphatidylinositol and phosphatidylcholine of the three fractions (7 and 45 mole per cent, respectively, of the total lipid). The TG contained the highest percentage of glycosylceramide (13 mole per cent). The PM had the highest percentage of phosphatidylserine (3 mole per cent) and nearly equal percentages of phosphatidylethanolamine (15 mole per cent and phosphatidylcholine (18 mole per cent). The most abundant sterols in membranes prepared from barley roots were stigmasterol (10 mole per cent), sitosterol (50 mole per cent), and 24zeta-methylcholesterol (40 mole per cent of the total sterol). Salt-treated plants contained a slightly higher percentage of stigmasterol than controls. The percentage of stigmasterol increased with age and a simple cause and effect relationship between salt treatment and sterol composition was not observed.

Evaluation of biochemical indicators of Fe and Mn nutrition for soybean plants. II. Superoxide dismutases, chlorophyll contents and photosystem II activity

Abstract The evaluation of nutritional status of plants through the use of biological indicators has been found useful when chemical analysis of the leaf nutrient concentrations does not reveal certain nutrient imbalances. In this work, the responses of Superoxide dismutases (SOD) isoenzymes, chlorophylls and photosystem II activity of leaves from soybean plants grown under different Fe and Mn nutrient levels were studied. Soybean plants, cv. Williams, were cultivated under growth chamber conditions in aerated nutrient solutions until the second trifoliate stage. At this time, first trifoliate leaves were sampled for biochemical analysis. Manganese and iron levels brought about modifications in the total SOD activity and in chlorophyll a and b contents. Isozyme Mn‐SOD and photosystem II activities, and the ratios chlorophyll a/b were clearly modified by Mn nutrient levels suggesting the specificity of these biochemical indicators for the appraisal of the Mn nutritional status of soybean plants. Correlatio...

ハツカダイコンおよびニンジンの生育と体内成分におよぼす施用窒素形態の影響

While radish and carrot plants, respectively, sensitive and tolerant to NH4+ were grown in aerated nutrient solutions containing NO3- or NH4+ or NO3- plus NH4+, growth and chemical constituents in their leaves and root portions were examined.The radish plants grew poorly in NH4+-solution, but well in solutions of NH4+ plus NO3-(10:>1). A large quantity of NH4+ was accumulated in the radish leaves with NH4+-supply, whereas the NH4+-level was 50% low with NH4+ plus NO3- (10:1) supply. The NH4+-toxicity on plant growth was thus overcome with the simultaneous supply of a small amount of NO3-. The values of titratable acidities in roots and leaves of the radish plants supplied with NH4+ were high, whereas those supplied with NH4+ plus NO3- were low and those supplied with only NO3- were the lowest.On the other hand, the carrot plants in NH4+-solution grew well and showed the similar growth with the NO3-fed plants. The carrot plants in the solution of NH4+ plus NO3- (10:1) also grew well. The carrot plants always contained lower NH4+ than radish plants with any nitrogen sources. The carrot plants showed almost the same value in titratable acidity regardless of any nitrogen sources.The contents of Ca and Mg per dry weight in radish and carrot plants were high with NO3--supply and low with NH4+-supply or with NH4+ plus NO3- (10:1) supply. The contents of K per dry weight in these plants were almost the same among NH4+-, NO3--, and NH4+ plus NO3--supplies. Besides, both radish and carrot plants grown in NO3--nutrition contained some organic acids at high levels per fresh weight, but those in NH4+- or NH4+ plus NO3--nutrition showed low contents of organic acids.The variations in contents of Mg, Ca, K per dry weight and of organic acids per fresh weight are not directly correlated with the NH4+-toxicity on growth; because in both radish and carrot, differences in the contents of Ca, Mg and organic acids between NH4+-fed plants and NO3--fed plants were observed, but no difference in these contents was observed between the NH4+-fed plants which grew poorly and the NH4+ plus NO3--fed plants which grew well. The NH4+-toxicity on radish growth is, thus, closely related to the increases of NH4+-level and titratable acidity in the leaves.