A. Gárate

Cadmium uptake and subcellular distribution in plants of Lactuca sp. Cd–Mn interaction

Abstract Cd uptake and subcellular distribution in (Lactuca sativa cv. Grandes Lagos) was studied. In vivo and in vitro experiments were carried out to study Cd effect on Mn uptake and subcellular distribution. Lettuce plants were grown in hydroponics with nutrient solutions containing 0.1 and 1.0 mg Cd l−1 in a greenhouse (in vivo experiments). Also, Cd was directly infiltrated on lettuce leaves in in vitro studies (0.5 and 1 mg Cd l−1), to minimize absorption and transport processes. Root and shoots were sampled after 16 days of exposure to the Cd solutions. Cd, Mn and other micronutrients were assessed in the different parts of the plant sampled and in the subcellular fractions obtained after wet mineralization, using A.A. spectrophotometry. Results show that Cd was accumulated in leaves mainly in cell wall fraction (64%) and this accumulation was fairly independent of Cd level in nutrient solution. The lowest Cd concentration (12–14%) was found in chloroplasts for both Cd levels tested. The increase in Cd concentration in the external medium caused an increase in Mn uptake and translocation to the shoots of lettuce plants, in contrast to the behavior of the other essential micronutrients, and an increase in Mn content in the chloroplasts, suggesting an interaction between Cd and Mn at the chloroplast level.

Alterations in the mineral nutrition of pea seedlings exposed to cadmium

Abstract A study was made of the effects of different levels of cadmium (Cd) in the nutrient solution (0.0, 1.5, and 6.0 mg/L Cd) on the assimilation of nitrate (NO3 ‐) and the uptake and distribution of cationic nutrients in pea (Pisum sativum cv. Argona) seedlings. Cadmium treatment resulted in an accumulation of NO3 ‐ in the root, indicating an alteration in NO3 ‐ translocation to the shoot. This was related to a decrease in the nitrate reductase (NR) activity in the shoot, severely inhibiting NO3 ‐ assimilation, and associated to a reduction in fresh tissue weight and in their relative water content. The concentration of potassium (K) decreased in both root and shoot, but its relative distribution between those tissues was not affected by the presence of Cd. Among other cationic nutrients, manganese (Mn) was the most affected, its concentration constantly decreased concomitantly with the increase in Cd supply. The distribution of Mn between shoot and root revealed that more was accumulated in the shoo...

Influence of cadmium on the uptake, tissue accumulation and subcellular distribution of manganese in pea seedlings

Pea (Pisum sativum L. cv. Argona) plants were challenged with Cd in a pure hydroponic system to study the effects on the uptake, tissue accumulation and subcellular distribution of Mn and Fe. This subcellular partitioning was compared to that of maize (Zea mays L. cv. Paolo) plants. In a long-term exposure experiment, Cd was supplied continuously with 0.0 (control), 10 or 50 μM Cd for 10 days. In a short-term treatment, pea plants were given 50 μM Cd for 72 h; this was followed by removing Cd from the nutrient solution and investigating the changes in the plants during the period of recovery from Cd toxicity for 96 h. The Relative Growth Increment (RGI) showed that plants treated with 10 μM Cd suffered moderate stress (70% of the control), whereas those given 50 μM experienced an strong phytotoxic effect (ca. 30%). In both experiments, Cd accumulated mostly in the roots (90% of the total plant concentration) and almost completely inhibited the uptake of Mn. Only when Cd was removed from the nutrient solution Mn uptake resumed. The relative distribution (%) of Mn between shoots and roots revealed that more Mn was found in shoots as Cd concentration increased in the nutrient solution (from 20% to ca. 50% in Cd-treated plants). Iron concentration and uptake showed less correlation with the Cd treatments. The exposure of pea plants to 10 μM and 50 μM Cd caused the severe depletion of Mn in all root subcellular fractions of pea and maize (Zea mays) plants. However, the Mn relative content (%) between subcellular fractions increased in the cell-wall containing fraction, but decreased in the soluble fraction. This effect was also observed in maize plants.

Boron and calcium distribution in nitrogen-fixing pea plants.

In a glasshouse experiment, plants of Pisum sativum L. cv. Argona were grown hydroponically with different B and Ca levels, in order to elucidate a specific role for B and Ca on the N(2) fixation in this temperate legume. The treatments were as follows: control (9.3 µM B and 2 mM Ca), -B (without B and 2 mM Ca), -B+Ca (without B and 3.6 mM Ca), +Ca (9.3 µM B and 3.6 mM Ca), -Ca (9.3 µM B and 0.4 mM Ca) and -Ca+B (46.5 µM B and 0.4 mM Ca). The supply of -Ca and +Ca did not affect nitrogenase activity, but the weight of old shoots and total N content increased with the Ca treatment. No symptoms of B deficiency were detected in the plants of the -B and -B+Ca treatments, apart from weight reduction in young shoots and lower nitrogenase activity. The B concentration decreased in young shoots and roots of plants grown without B (-B), but there was a sharper decrease in the roots of -B+Ca plants and the levels of B in the young shoots were similar to the control levels. The B concentration in -Ca plants was reduced in the old shoot and in the root, while plant weight and N content increased in -Ca+B plants. The cell wall and total B concentrations in the nodules were 4-fold compared with those of the roots. By contrast, the Ca root wall was 2.5 times higher than the nodule levels although total pectin was higher in the nodule than in the root. Finally, the results obtained showed that a high supply of Ca could induce B mobilisation from root to shoot. On the other hand, the high B requirement found in pea plant nodules may contribute to explain the low nitrogenase activity detected under -B conditions.

Effect of cadmium on nitrogen fixing pea plants grown in perlite and vermiculite 1

Abstract The effect of cadmium (Cd) on nitrogen (N2) fixing pea plants was studied. Perlite and vermiculite were compared as substrates in a hydroponic system where the plants were grown. In both experiments, there was no significant effect on nitrogenase activity when referred to fresh weight of nodules, but there was a reduction in the nodulation ratio (number of nodules developed per plant), even at low concentrations of available Cd. In plants grown in vermiculite, the nitrogenase activity expressed in terms of activity per nodule increased as Cd application increased; while in plants cultivated in perlite, that activity decreased when the applied Cd increased at the highest levels of Cd in the nutrient solution. Vermiculite had a significant interaction with the Cd in the nutrient solution, and therefore, we assume there was less Cd available to the plants than when perlite was used as the substrate. The loss of N2 fixation by the presence of Cd in plants grown in perlite has been related to a change...

Efficacy of commercial Fe(III)-EDDHA and Fe(III)-EDDHMA chelates to supply iron to sunflower and corn seedlings

Abstract Use of synthetic iron (Fe) chelates is the most common and effective way to treat Fe chlorosis in plants. Most commercial products contain Fe‐EDDHA or Fe‐EDDHMA but their efficacy can be quite different. Commercial products with EDDHA or EDDHMA as active components were chosen based on the data obtained by Lucena et al. (1992) in their chemical test. The chelates present extreme differences in behavior in the mentioned chemical tests. The analysis of the products revealed that the total Fe concentration is greater than the one indicated by the manufacturer in spite of a lesser amount of FeY‐ present. The plant response to these commercial products was tested using short‐term greenhouse hydroponic cultures. Sunflower and corn were chosen because of their different behavior under Fe‐stress conditions. No significant difference between plants treated with Fe‐EDDHA or Fe‐EDDHMA chelates were observed. Since the purity index indicates there are too many differences between commercial formulations of t...

A test to evaluate the efficacy of commercial Fe‐chelates

Abstract A large number of Fe fertilizers are used to correct iron chlorosis, most of them based on Fe‐EDDHA or Fe‐EDDHMA chelates. Our objective was to establish a laboratory test to evaluate in a rapid and simple way the capacity of a Fe‐chelate to maintain Fe in solution. The proposed test consisted of a two‐step procedure. First, the Fe‐chelate in solution was shaken with NaOH (pH=11.5) and after filtration (0.45 μm pore) pH is restored to 7.5. Next, the solution was treated with an excess (=600x) of the chelating agent DTPA. Red chelates, which present absorbances at 480 nm, were used in the test. Experimental conditions were initially studied using the speciation model Geochem and experimentally established. Fe concentration measured by atomic absorption and visible spectroscopy after the test application allowed us to obtain several indexes which indicated the chelate stability and were related to the concentration of Fe in the solution where plant roots grew. The test is useful in determining the ...

Iron-chelates evaluation in a calcareous soil

A greenhouse pot experiment withLolium multiflorum, cv. Tetila, grown in a calcareous soil was carried out to determine the efficiency of iron-chelate (Fe-EDTA,-DTPA,-EDDHA and Rexene) as soil amendments. In the soil solution Fe was displaced more readily from EDTA chelate and less so from EDDHA chelate. A significant increase of Mn, Cu and Zn in the soil solution was observed, with Fe-DTPA; Cu and Zn with Fe-EDTA; Cu with Rexene and, with Fe-EDDHA after 14 days. Plant took up more Fe from Rexene treatment than from the other treatments, Fe-EDDHA was the least efficient. In general, Mn, Cu and Zn concentrations in the leaf diminish in all the treatments compared with the control.

In vitro Stabilization and Distribution of Nitrate Reductase in Tomato Plants. Incidence of Boron Deficiency

Summary The addition of 1 mM cysteine, 2 % casein and 1010 polyvinylpyrrolidon (PVP) as protectants in the extraction (NRA) solution produced the highest nitrate reductase activity (EC 1.6.6.1) in tomato plants (Lycopersicon esculentum Mill. cv. Carmelo). The extraction medium was buffered at pH 7.7. NRA and nitrate concentration were higher in roots than in leaves. The opposite was observed for the insoluble-N fraction. A decrease of NRA in leaves and roots after 6 h of boron starvation was observed. The decay of the enzyme activity was higher in roots than in leaves. NRA was not affected by high concentrations of ammonia and glutamine in the incubation medium. Alterations observed in the concentrations of N-fractions might suggest an indirect effect of B deficiency on nitrate uptake and translocation of different Nsolutes in tomato plants.

Comparative study of the efficacy of commercial Fe chelates using a new test

Abstract At present, more than 100 iron fertilizers are on the Spanish market. The most efficient ones contain Fe‐EDDHA or Fe‐EDDHMA chelates as the basic component; however, different formulations cause plants to respond differently. In a previous paper we developed a new test to evaluate the relative stability of the Fe fertilizers against high pH (11.5) and competition with an excess of DTPA. In the present work, 31 formulations of chelates with red color (absorbance near 480 nm) are compared. Besides the application of the test, spectral properties, pH in solution and Fe content of the products have also been studied. Most of the commercial chelates present a similar behaviour after the test application, except that some of them have a greater resistance to competition with the DTPA. A few were largely destroyed after the test application. No significant differences were observed between Fe‐EDDHA and Fe‐EDDHMA fertilizers due to a large variability among chelates with the same base but different formu...