Effects of Various Concentrations of Iodine as Potassium Iodide on the Growth of Barley, Tomato and Pea in Nutrient Solution Culture

Iodine enhanced the height, number of tillers, fresh and dryweights of barley at concentrations of 0.5 and 1.0 ppm. With5.0 ppm the plants were indistinguishable from the untreatedcontrols. A dose of 10.0 ppm was inhibitory and induced symptomsof toxicity. In tomato, growth was increased at 0.5 ppm with maximum stimulationoccurring at 1.0 ppm. As in barley, 5.0 ppm exerted no effectand 10.0 ppm resulted in decreased growth, with toxicity symptomsevident. With pea, all iodine concentrations used led to reduced growth,the magnitude of the effect and the severity of the toxicitysymptoms increasing with concentration. The symptoms of toxicity in barley included general chlorosis,yellow intervenal patches, and brown necrotic spots. The lattertended to coalesce to form streaks. Death of some leaves resulted.Rather similar symptoms developed in tomato and pea, but nonecrotic spots were observed in the latter.     

Comparative accumulation of manganese and boron in barley tissues

Summary The uptake of Mn and B by barley plants was studied in a 5-week period in growth chambers. Fluorescent light was provided with an intensity of 3200 foot-candles in a 12-hour day length and the entire plants were grown at temperatures of 10°, 15°, or 20°C. The root medium consisted of a base nutrient solution in which Mn or B was added in the following concentrations: 0, 0.1, 0.5, 2.0, and 5.0 ppm. Five plants were grown in volumes of 20 liters of solution. At the end of the growth period the shoots and roots were analyzed for Mn and B. The Mn content of the roots increased with temperature and with the Mn concentration of the external solution while the B content remained virtually static regardless of temperature or solution concentration. The shoots were divided into young, mature, and old leaves. The Mn and B content of the old leaves showed increases which varied both with temperature and concentration. Similar results were obtained with young and mature leaves. The failure of B to accumulate in the roots was discussed. It was suggested that boric acid, with a very low degree of dissociation, is present largely in a molecular form and does not participate in the customary metabolic activity connected with ion uptake and accumulation in roots.     

Manganese nutrition effects on tomato growth, chlorophyll concentration, and superoxide dismutase activity

The effects of Mn nutrition of tomato (Lycopersicon esculentum Mill.) seedlings on Mn-, Fe- and CuZn-superoxide dismutase (SOD, EC 1.15.1.1) enzymatic activities, metal translocation, chlorophyll concentration, and plant growth were tested using a bioassay system consisting of chelator-buffered nutrient culture with Mn2+ activities set to pMn (-log activity of Mn2+) of 6.6, 7.6, 8.6, and 9.6. The two middle levels resulted in optimal plant growth, whereas the two extreme levels resulted in a gradual decrease in chlorophyll concentration and slower plant growth. At the end of the experiment, 26 days after transfer to the Mn treatments, significant differences in shoot Mn concentration were manifested, from 10.5 mg kg(-1) in plants grown in pMn 9.6 to 207.4 mg kg(-1) in plants grown in pMn 6.6. Other element concentrations in the leaf suggest that growth inhibition and chlorophyll synthesis were affected primarily by manganese deficiency and excess. Twenty days after transfer of plants to the Mn treatments Mn-, Fe- and CuZn-SOD activities were assayed in young expanded leaf tissues by electrophoresis running gel. Whereas chloroplastic CuZn-SOD activity did not differ among Mn treatments, the cytosolic CuZn-SOD and mitochondrial Mn-SOD activities increased in both Mn-excess and Mn-deficient plants.     

Interspecific root interactions and rhizosphere effects on salt ions and nutrient uptake between mixed grown peanut/maize and peanut/barley in original saline-sodic-boron toxic soil

Two glasshouse studies were conducted to investigate the effect of interspecific complementary and competitive root interactions and rhizosphere effects on the concentration and uptake of Na, Cl and B, and N, P, K, Ca, Mg, Fe, Zn and Mn nutrition of mixed cropped peanut with maize (Experiment I), and barley (Experiment II) grown in nutrient-poor saline-sodic and B toxic soil. Mixed cropped plants were grown in either higher density or lower density. The results of the experiment revealed that dry shoot weight decreased in peanut but increased in maize and barley with associated plant species compared to their monoculture. Shoot Na and Cl concentrations of peanut decreased significantly in both experiments, regardless of higher or lower density. The concentrations of Na also decreased in the shoots of mixed cropped maize and barley, but Cl concentrations increased slightly. The concentration of B significantly decreased in mixed cropping in all plant species regardless of higher or lower density. Rhizosphere chemistry was strongly and differentially modified by the roots of peanut, maize and barley, and mixed growing. There were significant correlations between the root-secreted acid phosphatases (S-APase), acid phosphatase in rhizosphere (RS-APase) and rhizosphere P concentration (RS-P) in the both experiments. The Fe-solubilizing activity (Fe-SA) and ferric reducing (FR) capacity of the roots were generally higher in mixed culture relative to their monoculture, which improved Fe, Zn and Mn nutrition of peanut. Further, there were also significant correlations among FR, Fe-SA and RS-Fe concentrations. Peanut facilitated P nutrition of maize and barley, while maize and barley improved K, Fe, Zn and Mn nutrition of peanut grown in nutrient-poor saline-sodic and B toxic soil.     

Manganese toxicity and marginal chlorosis of lettuce

Summary Romaine lettuce plants were grown in 15-liter tanks containing one-fifth strength Hoagland's solution over a range of Mn concentrations from zero to 10 ppm. This covered a span of Mn from deficiency to toxicity. Maximum yields were obtained at 0.1 and 0.5 ppm Mn supplied in the nutrient solution. A marginal chlorosis appeared at the highest Mn rates and was more pronounced in the older leaves. The plants were divided into young and old leaves and roots. The yellow borders of the old leaves were separated for analysis from the interior green tissues. The Mn content of the chlorotic borders averaged three times higher than that in the interior green tissues and reached a maximum of 5430 ppm Mn as opposed to 1940 ppm. The Fe content of the chlorotic bands was more than twice as high as that found in the green parts of the blades. The maximum content of Mn found in the roots was 3660 ppm. re]19720118     

Callose deposition in leaves of cowpea (Vigna unguiculata [L.] Walp.) as a sensitive response to high Mn supply

First macroscopic visible symptoms of Mn toxicity in cowpea (Vegna unguiculata [L.] Walp.) plants grown in solution culture were dark brown spots on the older leaves. Close to these spots, large quantities of substances which fluorescence with aniline blue were deposited, indicating formation of (1,3)-β-glucan (callose). Callose formation in the leaf epidermis was a more sensitive indicator of Mn toxicity than the appearance of macroscopic symptoms, or the Mn concentration in the leaf.     

The effect of manganese supply on exudation of carboxylates by roots of lucerne (Medicago sativa)

Some low-molecular-weight carboxylates commonly found in plant root exudates have the potential to increase the availability of Mn in the rhizosphere. Release of various compounds into the rhizosphere by plant roots may also be a mechanism by which certain species and genotypes are able to tolerate conditions of low Mn availability better than others. Lucerne (Medicago sativa L.) plants of Salado, a genotype tolerant to Mn deficiency, and Sirosal, an intolerant genotype, were grown in solution culture with 0, 5 or 500 nM Mn (Mn-0, Mn-5 and Mn-500). Exudates of whole root systems were collected at 14, 24 and 36 d and analysed by HPLC. Oxalate, tartarate, L-malate, lactate, malonate, maleate, citrate and succinate were detected and quantified in exudates under all Mn treatments. Malonate, citrate and succinate accounted for the majority of carboxylates in the exudates. Exudation increased with plant age, but amounts of individual carboxylates remained constant in proportion to the total amount exuded. A significant increase in exudation of all carboxylates other than malonate and maleate resulted from omission of Mn from nutrient solutions. Salado exuded more oxalate, tartarate, L-malate, lactate, citrate and succinate than Sirosal at Mn-0, and more citrate and succinate than Sirosal at Mn-5. Genotypic differences in carboxylate exudation under Mn-0 were associated with production of roots with diameter <100 μm. Plant Mn concentrations and growth rates suggested carboxylate exudation differences were not the sole factor responsible for differential tolerance to Mn deficiency in the lucerne genotypes.     

Supplemental manganese improves the relative growth, net assimilation and photosynthetic rates of salt-stressed barley

Previous results in our laboratory indicated that a reduced Mn concentration in the leaves of barley was highly correlated with the reduced relative growth and net assimilation rates of salt-stressed plants. If Mn deficiency limits the growth of salt-stressed barley, then increasing leaf Mn concentrations should increase growth. In the present study, the effect of supplemental Mn on the growth of salt-stressed barley ( Hordeum vulgare L. cv. CM 72) was tested to determine if a salinity-induced Mn deficiency was limiting growth. Plants were salinized with 125 mol m⁻³ NaCl and 9.6 mol m⁻³ CaCl₂. Supplemental Mn was applied in 2 ways: 1) by increasing the Mn concentration in the solution culture and 2) by spraying Mn solutions directly onto the leaves. Growth was markedly inhibited at this salinity level. Dry matter production was increased 100% in salt-stressed plants treated with supplemental Mn to about 32% of the level of nonsalinized controls. The optimum solution culture concentration was 2.0 mmol m⁻³, and the optimum concentration applied to the leaves was 5.0 mol m⁻³. Supplemental Mn did not affect the growth of control plants. Further experiments showed that supplemental Mn increased Mn concentrations and uptake to the shoot. Supplemental Mn increased the relative growth rate of salt-stressed plants and this increase was attributed to an increase in the net assimilation rate; there were no significant effects on the leaf area ratio. Supplemental Mn also increased the net photosynthetic rate of salt-stressed plants. The data support the hypothesis that salinity induced a Mn deficiency in the shoot, which partially reduced photosynthetic rates and growth.     

Combined deficiency of iron and other divalent cations mitigates the symptoms of iron deficiency in tobacco plants

To determine the responses of plants to deficiencies of multiple metals, tobacco plants ( Nicotiana tabacum L.) were subjected to treatments that were deficient in combinations of Fe and two other micronutrients, Zn and Mn. The response was measured using macro indices, including plant appearance, FW, chlorophyll concentration, and mineral concentrations, and with a molecular index, the barley ( Hordeum vulgare L.) Ids2 promoter / GUS fusion gene system (Yoshihara et al. 2003, Plant Biotech 20: 33–41). Tobacco plants grown in medium with combined deficiencies grew better and had higher chlorophyll concentrations than did plants grown on medium deficient in Fe only, although the measured Fe concentrations in the plant tissues were essentially the same. The Ids2/GUS expression responded to Fe deficiency, but not to Mn or Zn deficiencies in tobacco plants when Fe was present. Tobacco plants grown in medium with combined deficiencies had clearly detectable GUS activity, but the response was significantly lower than that in tobacco plants deficient in Fe only. The Fe-deficiency symptoms were mitigated at both the visible and molecular levels. Although more precise experimental evidence is needed to explain the mitigation mechanism, the balance of minerals was shown to be an important parameter to consider when estimating iron deficiency based on tobacco plant responses.     

The effect of manganese-oxidizing bacteria and pH on the availability of manganous ions and manganese oxides to oats in nutrient solutions

Summary The uptake of Mn from manganous ions (Mn-ions) and pyrolusite (MnO₂) by three week-old oat plants (Avena sativa L.) grown in nutrient solutions controlled at pH values between 6 and 8, was almost completely inhibited by suspensions of Mn- oxidizing bacteria over a three day uptake period.Grey speck symptoms of Mn deficiency developed in oats grown for 10 days with Mn bacteria in a nutrient solution that had received 1 ppm Mn ions and was controlled at pH 6.3. Rape plants (Brassica napus L.) absorbed appreciable amounts of Mn from treatments similar to those that inhibited Mn uptake by oats.Treatments which decreased or prevented biological oxidation of Mn ions favoured the uptake of Mn by oats from Mn ions, MnO₂ and bacterial Mn-oxide. Acid conditions (pH 5.0) always increased Mn uptake. This was due in part to inhibition of bacterial oxidation and to an increase in the ability of the plants to obtain Mn from Mn oxides.Uptake of Mn is explained on the basis of the rates of two opposing processes; the rate of release of Mn from oxides and the rate of biological oxidation of Mn ions. The results are discussed in relation to the availability of Mn in soils.     

Genotypic effects in phytoavailability of radiocaesium are pronounced at low K intensities in soil

The differences in radiocaesium uptake between species were analysed in a series of solution culture and pot trials. Since radiocaesium uptake is very sensitive to the solution potassium (K) concentration, it was hypothesised that species depleting K in the rhizosphere to a larger extent, will have a higher radiocaesium uptake. Five species (bean, lettuce, winter barley, ryegrass and bentgrass) were grown for 18–21 days in nutrient solution spiked with ¹³⁷Cs and at 4 K concentrations between 0.025 and 1.0 mM. Shoot ¹³⁷Cs activities all decreased between 17- and 81-fold with increasing K supply. Shoot ¹³⁷Cs activities were 4-fold different between species at the lowest K supply and 3.4-fold different at high K supply. The same five species were grown in two ¹³⁴Cs spiked soils with contrasting exchangeable K but similar clay content. Shoot ¹³⁴Cs activities were up to 19-fold higher in the soil with lowest exchangeable K. Differences in shoot activity concentrations between the species were only 4.5-fold in the high K soil, but were 15-fold in the low K soil. Bulk soil solution ¹³⁴Cs and K concentration data were combined with radiocaesium uptake characteristics measured in solution culture to predict radiocaesium uptake from soil. Predictions were within 1.6-fold of observations in the high K soil but largely underestimated ¹³⁴Cs uptake in lettuce, ryegrass and barley in the low K soil. A solute transport model was used to estimate K and radiocaesium concentrations in the rhizosphere. These calculations confirmed the assumption that higher radiocaesium uptake is found for species that deplete K in the rhizosphere to a larger extent.     

The absorption of potassium as influenced by its concentration in the nutrient medium

Summary Barley plants were grown, for periods of up to eleven weeks duration, in culture solutions in which the potassium concentrations were maintained at 0.01, 0.10, 1.0, and 50.0 ppm. Potassium added continuously during the day was augmented night and morning, as determined by solution analysis. The following observations were made:Plants grew equally well at pH levels of 5.5 and 7.0. Variations in root temperature between 15° and 25°C had no effect on K-content of tissue at either pH level. Yields were large as were the quantities of potassium absorbed from the solutions. No potassium-deficiency symptoms were observed at any of the concentrations used.Considerable variation in yield was observed between tanks and between plants growing in the same tank. The variation appeared to be due to a difference in the amount of tillering per plant.The results indicate that plants grow well in culture solutions at potassium concentrations approaching 0.01 ppm and this may have some implications on the mechanism of uptake of potassium by plant roots growing in a soil system.     

Effects of Concentration and Time of Exposure on the Phytotoxicity of Linuron

When seedlings of lettuce and turnip were grown in nutrientsolutions containing different concentrations of linuron, theconcentration in the shoot at the time when toxicity symptomsappeared was related to the solution concentration. With lettuce,for example, symptoms were recorded after 7 d at 0.15 µg/mland the shoot concentration was 2.7 µg/g fresh wt. At0.06 µg/ml, symptoms appeared after 10 d and the shootconcentration was then 1.1 µg/g fresh wt. If grown fordifferent periods in solutions containing linuron and then transferredto fresh nutrient solutions containing no herbicide, turnipor lettuce seedlings which had accumulated 0.7–0.8 µglinuron/g fresh wt developed toxicity symptoms 4 to 6 d later.Seedlings were also treated with linuron after they had grownfor different periods in control nutrient solutions. The shootconcentrations attained before toxicity symptoms appeared werehigher in those seedlings which were larger when herbicide treatmentbegan. These results show that the herbicide concentration insolution, time of exposure, and age of seedling are interrelatedin determining linuron phytotoxicity.     

Isolation and identification of a potent allelopathic substance in rice root exudates

A search for growth inhibitors in rice root exudates was undertaken in order to clarify the allelopathic system in rice ( Oryza sativa L.). Rice seedlings inhibited the growth of cress ( Lepidium sativum L.) and lettuce ( Lactuca sativa L.) seedlings when the cress and lettuce were grown with rice seedlings. The putative compound causing the inhibitory effect of rice seedlings was isolated from their culture solution, and the chemical structure of the inhibitor was determined by spectral data as momilactone B. Momilactone B inhibited the growth of cress and lettuce seedlings at concentrations greater than 3 and 30 µ M , respectively. The concentration of momilactone B was 3.4 and 1.1 nmol per seedling in the culture solutions of husked and non-husked rice seedlings, respectively. These results suggest that rice seedlings may release momilactone B into the environment and the stress caused by the husk-treatment may increase the amount of momilactone B released. Thus, momilactone B may play an important role in rice allelopathy.     

Role of manganese in low-pH-induced root hair formation in<Emphasis Type="Italic"> Lactuca sativa</Emphasis> cv. Grand Rapids seedlings

Root hair formation is induced by low pH in lettuce (Lactuca sativa L. cv. Grand Rapids) seedlings cultured in mineral medium. The role of mineral concentrations in this phenomenon was investigated, especially for manganese. When lettuce seedlings were cultured in media that were deficient in calcium (Ca), manganese (Mn), boron (B) or molybdenum (Mo), morphological changes were induced in roots. Deficiency of other nutrients had little effect on root hair formation. Ca or B deficiency inhibited the growth of the main root and the formation of root hairs, regardless of pH. Mn or Mo deficiency increased root hair formation at pH 6 and suppressed main root growth slightly. In contrast, increasing the Mn concentration suppressed low-pH-induced root hair formation. The Mn content of roots grown at pH 4 was only about 15% of that at pH 6. In contrast, the Mo content of roots grown at low pH was about six times that of roots grown at neutral pH. These results suggest that root hair formation induced by low pH is at least partly mediated by decreased Mn uptake in root cells.     

Assessing the Tolerance of Castor Bean to Cd and Pb for Phytoremediation Purposes

This study evaluated Cd and Pb accumulation by castor bean (Ricinus communis cv. Guarany) plants grown in nutrient solution, aiming to assess the plant’s ability and tolerance to grow in Cd- and Pb-contaminated solutions for phytoremediation purposes. The plants were grown in individual pots containing Hoagland and Arnon’s nutrient solution with increasing concentrations of Cd and Pb. The production of root and shoot dry matter and their contents of Cd, Pb, Ca, Mg, Cu, Fe, Mn, and Zn were evaluated in order to calculate the translocation and bioaccumulation factors, as well as toxicity of Cd and Pb. Cadmium caused severe symptoms of phytotoxicity in the plant’s root and shoot, but no adverse effect was observed for Pb. Castor bean is an appropriate plant to be used as indicator plant for Cd and tolerante for Pb in contaminated solution and it can be potentially used for phytoremediation of contaminated areas.     

The Effect of Micro-organisms on the Absorption of Inorganic Nutrients by Intact Plants: II. UPTAKE AND UTILIZATION OF PHOSPHATE BY BARLELY PLANTS GROWN UNDER STERILE AND NON-STERILE CONDITIONS

The uptake of phosphate by barley plants grown under sterileand non-sterile conditions has been compared from solutionsranging in concentration between 0.001 to 10.0 ppm P. If specialprecautions are not taken to exclude microorganisms their activityon or in plant roots greatly modifies the absorption and utilizationof phosphate in plants, especially when the external concentrationis low. More phosphate is incorporated into nucleic acids, phospholipids,and phosphoproteins in the roots; at 0.001 ppm P these compoundsaccount for over 60 per cent of the phosphate absorbed comparedwith about 15 per cent in plants grown under sterile conditionsand even at 1.0 ppm P there is a twofold difference. The immobilizationof phosphate in the roots reduces its transfer to the shoots;at 0.001 ppm P, 2 as compared with 20 per cent of the phosphateabsorbed is transferred to the shoots. This effect decreaseswith increasing concentration but small differences are stillapparent up to about 0.5 ppm P. A further effect of micro-organisms is apparent when plantsare transferred from dilute solutions to phosphate-free solutions.Under non-sterile conditons there is an almost tenfold increasein the loss to these solutions of previously absorbed phosphate. It is evident that conclusions on the mechanism of absorptionof phosphate, based on experiments in which the actions of micro-organismshave been ignored, require reinvestigation.     

Factors effecting the toxicity of nitrite nitrogen to tomatoes

Experiments were done to study the effects of nitrite nitrogen on nutrient absorption and organic acid content of tomatoes (Keystone) grown in sand culture. The effects of root aeration, magnesium and iron supply on the symptoms of nitrite toxicity were also studied. Nutrient solutions were standardised to pH 4.5 and contained from 0–250 ppm nitrite nitrogen. Increasing the concentration of nitrite nitrogen decreased dry matter yields, total acidity, the concentration of nitrogen, phosphorus and potassium in tomato plants, and increased the chlorosis of leaves and the lignification of roots. Shortage of iron, magnesium, and poor root aeration caused toxicity symptoms to appear at a smaller concentration of nitrite nitrogen and increased the severity of the symptoms.     

Soil fumigation with methyl bromide: bromide accumulation by lettuce plants

Lettuce plants grown in beds of soil previously fumigated with methyl bromide accumulated water-extractable bromide, the amount present in the tissues depending on the concentration of inorganic bromide produced in the soil by the breakdown of the fumigant. Samples of lettuce plants from commercial nursery soils fumigated with methyl bromide at rates of 1–2 lb/ 100 ft² (49–98 g/m²) gave rise to soil bromide levels of n-6i/μg/g. The corresponding bromide concentrations in the plants ranged from i-6 to io-1 mg/g of dry tissue. The bromide concentrations in whole lettuce plants grown in pots of soil supplemented with 0–5 mg/g inorganic bromide, as potassium bromide, ranged up to 100 mg/g of dry tissue. Bromide taken up from the soil by lettuce plants was located mainly in the outer leaves. Lettuce was relatively insensitive to the presence of bromide in the soil; no phytotoxic symptoms were observed in plants growing in soils containing 5 mg/g inorganic bromide. Implications in relation to possible tolerance limits for the bromide content of lettuce plants are discussed.     

Genetic differences in phosphorus absorption among white clover populations

Summary Eight semi-natural white clover populations and two cultivars were grown in culture solutions containing 10 ppm and 0.01 ppm phosphorus (P). The rate of P uptake by the intact plants was then measured in solutions containing 10 ppm P.Phosphorus uptake per unit root length was twice as great by plants previously grown at 0.01 ppm P than those grown at 10 ppm P. Large differences in total P uptake were found among populations regardless of the pretreatment; most of this variation was accounted for by differences in root length. Only small differences were found between populations for P uptake per unit root length, and then only after pretreatment with 10 ppm P; this variation was largely accounted for by relative growth rate and shoot %P.