Pilar Zornoza

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.

Efficiency of white lupin in the removal of mercury from contaminated soils: Soil and hydroponic experiments

This study examined the ability of the white lupin to remove mercury (Hg) from a hydroponic system (Hg concentrations 0, 1.25, 2.5, 5 and 10 micromol/L) and from soil in pots and lysimeters (total Hg concentration (19.2 +/- 1.9) mg/kg availability 0.07%, and (28.9 +/- 0.4) mg/kg availability 0.09%, respectively), and investigated the accumulation and distribution of Hg in different parts of the plant. White lupin roots efficiently took up Hg, but its translocation to the harvestable parts of the plant was low. The Hg concentration in the seeds posed no risk to human health according to the recommendations of the World Health Organization, but the shoots should not be used as fodder for livestock, at least when unmixed with other fodder crops. The accumulation of Hg in the hydroponically-grown plants was linear over the concentration range tested. The amount of Hg retained in the roots, relative to the shoots, was almost constant irrespective of Hg dose (90%). In the soil experiments, Hg accumulation increased with exposure time and was the greater in the lysimeter than in the pot experiments. Although Hg removal was the greater in the hydroponic system, revealing the potential of the white lupin to extract Hg, bioaccumulation was the greatest in the lysimeter-grown plants; the latter system more likely reflects the true behaviour of white lupin in the field when Hg availability is a factor that limits Hg removal. The present results suggest that the white lupin could be used in long-term soil reclamation strategies that include the goal of profitable land use in Hg-polluted areas.

Mitigation of Cu stress by legume-Rhizobium symbiosis in white lupin and soybean plants

The effect of Bradyrhizobium-legume symbiosis on plant growth, toxicological variables and Cu bioaccumulation was studied in white lupin and soybean plants treated with 1.6, 48, 96 and 192 μM Cu. In both species, those plants grown in the presence of root nodule-forming symbiotic Bradyrhizobium showed less root and shoot growth reduction, plus greater translocation of Cu to the shoot, than those grown without symbiotic Bradyrhizobium. The effective added concentrations of Cu that reduced shoot and root dry weight by 50% (EC50), and the critical toxic concentration that caused a 10% reduction in plant growth (CTC10%), were higher in plants grown with symbiotic Bradyrhizobium, and were in general higher in the roots whether the plants were grown with or without these bacteria. The production of malondialdehyde and total thiols was stimulated by Cu excess in the shoots and roots of white lupin grown with or without symbiotic Bradyrhizobium, but mainly in those without the symbionts. In contrast, in soybean, the increases in malondialdehyde and total thiols associated with rising Cu concentration were a little higher (1.2-5.0 and 1.0-1.6 times respectively) in plants grown with symbiotic Bradyrhizobium than without. Finally, the organ most sensitive to Cu excess was generally the shoot, both in white lupin and soybean grown with or without symbiotic Bradyrhizobium. Further, Bradyrhizobium-legume symbiosis appears to increase the tolerance to Cu excess in both legumes, but mainly in white lupin; plant growth was less reduced and CTC10% and EC50 values increased compared to plants grown without symbiotic Bradyrhizobium. Bradyrhizobium N2 fixation in both legumes would therefore seem to increase the phytoremediation potential of these plants when growing on Cu-contaminated sites.

Seasonal Effect on Growth Parameters and Macronutrient Use of Sweet Pepper

ABSTRACT Sweet pepper plants (Capsicum annuum L.) grown under greenhouse conditions differed widely in the rate of production of their total dry mass and their harvestable weight, although there was not shortage in water or nutrient supply. Plants were grown in aerated nutrient solutions along two different growing seasons. The differences in plant productivity were mainly due to the environmental conditions of the growth cycle. During the increasing day length season, from the beginning of spring to summer (13.0 to 14.8 h day− 1), plants produced the largest amount of fruits, but with a 10% blossom-end rot incidence. In the season of short photoperiod, progressing from the beginning of autumn to winter with 13.3 to 10.3 light h day− 1, the total dry weight and yields gradually decreased, but blossom-end rot in fruit did not appear. Different growth patterns were found for morphological and physiological parameters, because of the different light loads received by the canopy, being adjusted to the seasonal variables. Reduced light load markedly reduced leaf area and leaf thickness, but increased specific leaf area, which gave plants an increased ability to intercept light. Not only the amount of initial biomass, but radiation and the age of the pepper plants were the main growing driving factors, influencing relative growth rate, nitrogen (N)-use efficiency, and calcium (Ca) partitioning. Moreover, mathematical approaches for prediction of biomass production and N accumulation as a function of radiation are given in order to establish in the future a sweet pepper growth model.

Varietal specificity in growth, nitrogen uptake, and distribution under contrasting forms of nitrogen supply in spinach

Variations in nutrient uptake, growth and nitrogen (N) distribution under contrasting forms of N supply were studied in three spinach cultivars. The varieties (Viroflay, Butterflay, and Giant) were smooth, curly, and semi-curly leaved, respectively. The plants were grown hydroponically with two nitrate:ammonium (NO 3 :NH 4 ) ratios (100:0 and 80:20). Giant grown with both N forms displayed an increase of total N and potassium (K) absorption compared with that of those grown with NO 3 alone, by growing more and having tissues with greater capacity for NH 4 detoxification, i.e., they made better use of N supplied as NO 3 plus NH 4 . Mixed N nutrition in Butterflay caused the nutrient uptake to be reduced strongly and lower plant growth, the root being unable to assimilate NH 4 . Irrespective of the NO 3 :NH 4 ratio supplied to Viroflay, the uptake of K, calcium (Ca), and magnesium (Mg) did not vary, but NO 3 uptake, growth, and N distribution were negatively affected by the presence of NH 4 . Finally, the results obtained suggest that potentially useful specificity exists among these spinach cultivars for N form preference and for tolerance of NH 4 . This may partly be due to their genetic ability of NH 4 detoxification in the roots and partly to the form in which the N is retained or transported to the shoot.

A possible role for boron in higher plants

Abstract The influence of boron on flavonoid metabolism in leaves of tomato plants (Lycopersicon esculentum Mill, cv. Marglobe) was investigated. A significantly higher rate of total flavonoid was observed from a B‐deficiency in the nutrient medium. This effect was noted during the last periods of culture cycle. On the other hand, B deficient leaves showed a total absence of flavonols usually present in this tissue. The qualitative differences among various levels were a higher flavone: flavanone ratio, whereas B excess treatment shows the opposite effect. These results suggest a role for B in higher plants as a regulator of flavonoid biosynthesis.

Intraspecific differences in nitrogen assimilating enzymes in spinach under contrasting forms of nitrogen supply 1

Abstract Intraspecific differences in the activities of nitrate reductase (NR), glutamine synthetase (GS), NADH dependent glutamate synthase (NADH‐GOGAT), and glutamate dehydrogenase (GDH) under contrasting forms of nitrogen (N) supply were studied in tissues of three spinach (Spinacia oleracea L.) cultivars. The varieties (Viroflay, Butterflay, and Giant) were smooth, curly and semicurly leaved, respectively. The plants were grown in nutrient solutions containing NO3 as the sole source of N (100:0) and NO3 plus NH4 (80:20). Giant, the NH4 tolerance of which had been evaluated in growth and on the basis of nutrient uptake, had much higher GS and GDH activities in the roots and higher NR and NADH‐GOGAT levels in the leaves of plants grown on NO3 and NH4 than that grown on NO3 alone. On the level of N assimilating enzymes of Butterflay, mixed N nutrition caused an increase of GDH and NADH‐GOGAT in leaves and roots and at the same time a decrease of GS in the roots and NR in the leaves. An inverse relationsh...

Incidence of P, Mn and B deficiencies on the levels of the whole and individual flavonoid groups in tomato leaves

Abstract Alterations occur in the normal content of total and individual flavonoids with P, Mn and B deficiencies, in tomato leaves. P and Mn deficiencies do not alter the total flavonoid level. Nevertheless, these deficiencies lead to different contributions of each flavonoid group (flavonols, flavones and flavanones) to the whole content. B deficiency produces a very significant increase in total flavonoid content. Compounds that contribute the most to this accumulation are flavones.

Response of Lupinus albus to Pb–EDTA indicates relatively high tolerance

ABSTRACT White lupin plants were grown in hydroponics with 0, 90 and 180 µmol L−1 Pb(II) ethylenediaminetetraacetate complex for 30 days. Pb distribution (shoot/root ratio) was 0.34 and 0.46 for both Pb treatments. In the shoots, no decrease in biomass nor in photosynthetic pigment levels and no changes in the concentrations of malondialdehyde and glutathione were detected. In the roots, malondialdehyde increased by 20%, glutathione 2–3.6 times and phytochelatin concentrations 4–5 times. The high tolerance of white lupin makes it a valuable plant for phytoremediation of Pb-contaminated soil.