Acquisition of phosphorus and copper by VA-mycorrhizal hyphae and root-to-shoot transport in white clover

White clover (Trifolium repens L.) plants were grown in a calcareous soil in pots with three compartments, a central one for root growth and two outer ones for growth of vesicular-arbuscular (VA) mycorrhizal (Glomus mosseae [Nicol. & Gerd.] Gerdemann & Trappe) hyphae (hyphal compartments). Phosphorus (P) was applied at three levels (0, 20 and 50 mg kg⁻¹ soil) in the outer compartments in mycorrhizal treatments. Root and shoot dry weight were increased in mycorrhizal plants with hyphal access to outer compartments. Growth of the mycorrhizal hyphae in the outer compartments was not significantly affected by variation in P level in these compartments. However, both concentration and amount of P in roots and shoots sharply increased with increasing P supply in the outer (hyphal) compartments. With increasing P levels the calculated delivery of P by the hyphae from the outer compartments increased from 34% to 90% of total P uptake. Hyphal access to the outer compartments also significantly increased both concentration and quantity of Cu in the plants. The calculated delivery of Cu by the hyphae from the outer compartments ranged from 53% to 62% of total Cu uptake, irrespective of the P levels and the amounts of P taken up and transported by the hyphae. However, the distribution of Cu over roots and shoots was largely dependent on P levels. With increase in P level in the outer compartments the calculated hyphal contribution to the total amount of Cu in the shoots increased from 12% to 58%, but decreased in the roots from 75% to 46%. In conclusion, uptake and transport by VA-mycorrhizal hyphae may contribute substantially not only to P nutrition, but also to Cu nutrition of the host.     

The role of phytosiderophores in acquisition of iron and other micronutrients in graminaceous species: An ecological approach

Phytosiderophores (PS) are released in graminaceous species (Gramineae) under iron (Fe) and zinc (Zn) deficiency stress and are of great ecological significance for acquisition of Fe and presumably also of Zn. The potential for release of PS is much higher than reported up to now. Rapid microbial degradation during PS collection from nutrient solution-grown plants is the main cause of this underestimation. Due to spatial separation of PS release and microbial activity in the rhizosphere a much slower degradation of PS can be assumed in soil-grown plants. Concentrations of PS up to molar levels have been calculated under non-sterile conditions in the rhizosphere of Fe-deficient barley plants.Besides Fe, PS mobilize also Zn, Mn and Cu. Despite this unspecific mobilization, PS mobilize appreciable amounts of Fe in calcareous soils and are of significance for chlorosis resistance of graminaceous species. In most species the rate of PS release is high enough to satisfy the Fe demand for optimal growth on calcareous soils.In contrast to the chelates ZnPS and MnPS, FePS are preferentially taken up in comparison with other soluble Fe compounds. In addition, the specific uptake system for FePS (translocator) is regulated exclusively by the Fe nutritional status. Therefore, it seems appropriate to retain the term phytosiderophore instead of phytochelate.     

The effect of copper toxicity on the contents of nitrogen compounds in Silene vulgaris (Moench) Garcke

The effect of copper on the uptake of nitrogen and the tissue contents of inorganic nitrogen, amino acids and proteins were studied in cooper-sensitive Silene vulgaris (Moench) Garcke, grown at different nitrogen sources (NH₄ ⁺ or NO₃ ^-). All the toxic copper levels tested, i.e. 4, 8, 16 M Cu²⁺, strongly inhibited the uptake of nitrogen, especially of NO₃ ^-, and decreased the content of NO₃ ^-, amino acids and proteins. Especially at 4 and 8 M Cu²⁺, NH₄ ⁺ accumulated in the plants, suggesting that the conversion of NH₄ ^- into amino acids was inhibited.     

Characterization of amine oxidases from pisum, lens, Lathyrus and Cicer

Amine oxidases have been purified to homogeneity from Pisum sativum, Lens esculenta, Lathyrus sativus and Cicer arietinum. The enzymes have a M_r. of 150 000 and are composed of two identical subunits of 72 000. The amine oxidases showed an isoelectrophoretic heterogeneity.     

Comparative studies of nickel,cobalt, and copper uptake by some nickel hyperaccumulators of the genus Alyssum

The uptake of Ni, Co, and Cu by the nickel hyperaccumulator Alyssum troodii Boiss and the non-accumulator Aurinia saxatilis (L.) Desv. were studied in pot trials using artificial rooting media with varying concentrations of the metals added as soluble salts, singly and in combination. The ability of five other Ni hyperaccumulating species of Alyssum to hyperaccumulate Co was also investigated.Leaves and stems of A. troodii accumulated Ni to almost the same extent (8000–10 000 g g^-1). In roots, the highest Ni concentration was 2000 g g^-1. In leaves of Au. saxatilis, the maximum Ni concentration was only 380 g g^-1 and the level in roots was even lower.In media containing Co, the maximum concentration of this element in A. troodii (2325 g g^-1) was ten times higher than in the non-accumulator species. Slightly less Co was found in stems and roots of both species. Among the other Ni hyperaccumulators, the maximum concentration of Co in leaves ranged from about 1000–8000 g g^-1.Copper concentrations were the same in all organs of both species when they were grown in copper-rich media and were in the range 40–80 g g^-1, showing that neither plant was capable of taking up Cu at levels comparable to those of Ni and Co.When both plants were grown in media containing equal amounts of both Co and Ni, the Co concentrations in plant organs were the same as for specimens grown in media containing Co only. However, the Ni levels were lower in both species. Uptake of Co therefore appeared to suppress Ni uptake.Pot trials showed that the order of tolerance was Ni>Cu>Co for A. troodii and Ni>CoCu for Au. saxatilis, whereas the seedling tests showed the order to be Co>Ni>Cu. At metal concentrations 10 000 g g^-1, the overall tolerance of A. troodii was greater than that of Au. saxatilis which exhibited equally low tolerance to Ni and Cu.We conclude that in A. troodii, A. corsicum Duby, A. heldreichii Hausskn., A. murale Waldstein & Kitaibel, A. pintodasilvae T.R. Dudley, and A. tenium Hálácsy, Ni tolerance and hyperaccumulation conveys the same character towards Co. This behaviour should be investigated in other hyperaccumulators of Ni and/or Co.     

Role of magnesium in combination with liming in alleviating acid-soil stress with the aluminium-sensitive sorghum genotype CV323

An experiment to study the effects of Mg nutrition on root and shoot development of the Al-sensitive sorghum (Sorghum bicolor (L.) Moench) genotype CV323 grown in pots of sandy loam under different acid soil stress is reported. This experiment had a factorial design: four rates of liming were combined with four rates of Mg fertilization. When no Mg was added, the pH of the soil solutions (collected in ceramic cups) increased from 4.0 (unlimed) to 4.2, 4.7 and 5.9 at the increasing rates of liming. After 30 days of growth dry matter yields of the limed treatments were 40%, 115% and 199% higher than that of the unlimed treatment. Without liming and at the highest liming rate, adding Mg did not affect plant biomass significantly. At the two intermediate levels of liming, however, 11.3 mg extra Mg per kg soil increased dry matter yield to the same levels as found at the highest liming rate. Concentrations of Mg in the soil solution rose after Mg was added and fell when lime was added, but adding both Mg and lime increased Mg concentrations in the plant shoots. In plants of the limed treatments, dry matter yield was correlated closely with the Mg concentration in the shoot. This was not so in the unlimed treatment. Furthermore, in the unlimed treatments root development was inhibited, but reduced Mg uptake by the plants resulted mainly from the direct effect of Al- (or H-) ions in the soil solution rather than from impaired root development. It is concluded that Mg fertilization counteracted the interfering effects of Al- and H ions on Mg uptake.     

Copper and zinc in experimental hypertension

The role of the trace minerals, copper (Cu) and zinc (Zn) are important in maintaining blood pressure. Copper has been found to inhibit the activity of angiotensin's converting enzyme. An interrelationship has been found to exist between Cu and Zn. Data in renal (RH) and spontaneous hypertensive rates (SHR) regarding Cu and Zn is lacking. The purpose of this report was to measure Cu and Zn levels in two types of experimental animal models of hypertension compared to normotensive (NT) rats. Blood samples were drawn to measure serum levels of Cu and Zn in three types of animals, RH, SHR, and NT. Serum Cu values were found to be lower, whereas Zn levels were elevated in the SHR animals. Serum levels of Cu and Zn in the RH animals were similar to those found in the NT animals. Further study of the interaction of those trace minerals is documented, and extends over knowledge of the role of minerals in blood pressure control.     

Effect of ferric nitrilotriacetate on rostral mesencephalic cells

After murine fetal cells from the rostral mesencephalic tegmentum were isolated, prepared, and cultured; neuronal and glial cells in primary mixed cell cultures were exposed to ferric nitrilotriacetate (Fe-NTA) at varying concentrations. Studies were performed at 23 days in culture after 14 day exposure to Fe-NTA. In addition to morphologic studies, biochemical assays including specific [³H]flunitrazepam (FLU) binding, clonazepam (CLO)-displaceable [³H]-FLU binding, Ro5-4864-displaceable [³H]-FLU binding, [³H]dopamine (DA) uptake, [³H]haloperidol (HAL) binding, [³H]spiperone (SP) binding, glutamine synthetase activity (GS), and protein determinations were performed. The data demonstrate that chelated ferric iron has an adverse effect on these cells. The data also demonstrate that increasing concentrations of Fe-NTA resulted in massive neuronal dropout leaving the culture population virtually all glial; however, the specific binding of [³H]HAL and [³H]SP increased. There was a concomitant decrease in both glutamine synthetase activity and overall protein content. The mechanism of enhancement in the presence of Fe-NTA of [³H]HAL and [³H]SP binding is unknown and may be unique, but may be related to the known increase in D₂ receptor ligand affinity in the presence of other multivalent cations (Ca²⁺ and Mg²⁺).