Evidence for a role of calcium in nitrate assimilation in wheat seedlings

Severely Ca-deficient Triticum aestivum L. seedlings accumulated high levels of nitrite and moderate levels of nitrate and organic nitrogen, but contained unaltered levels of hydroxylamine. Nitrite accumulation was not related to molybdenum deficiency, or altered cellular pH. Nitrate reductase was decreased by Ca deficiency, apparently by repression of enzyme synthesis from accumulated nitrite and not by inhibition of enzyme activity. Nitrite reductase and NADP diaphorase activities were not affected by Ca deficiency, and Ca did not restore activity to nitrite reductase inactivated by cyanide. The results indicated that the role of Ca is in intracellular transport of nitrite and not in induction or activity of enzymes.     

Mineral nutrition of cacao (Theobroma cacao L.)

Summary Two experiments on cacao seedlings grown in sand culture are described, the first of which was concerned with variations in the levels of nitrogen, phosphorus, potassium, calcium, magnesium and sulfur (the macronutrient experiment) and the second dealing with variations in the levels of iron, copper, zinc, boron, manganese, and molybdenum (the micronutrient experiment).Many of the deficiency symptoms obtained were similar to those reported in the literature and they have not been described again. However, additional information is provided for symptoms of phosphorus, potassium, calcium, iron, manganese, copper, boron, and molybdenum deficiencies.The effects of all treatments on the dry weights of leaves, stems, and roots are presented. The effects of the macronutrient treatments on the levels of nitrogen, phosphorus, potassium, calcium, and magnesium in the leaves of eight month old plants and the effects of micronutrient treatments on the levels of nitrogen, phosphorus, potassium, calcium, magnesium, iron, manganese, copper, zinc, boron, molybdenum, sodium, and aluminium in the leaves of eleven-month-old plants are presented and discussed.     

Nitrogen assimilation and protein synthesis in wheat seedlings as affected by mineral nutrition. I. Macronutrients

Deficiencies of each macronutrient (N, P, K, Ca. Mg, S, and Fe) decreased the specific activity of nitrate reductase from Triticum aestivum L. seedlings. Nitrate content was decreased by N, P, K, Ca, and Mg deficiencies and unaffected by S and Fe deficiencies. Glutamic acid dehydrogenase activity was decreased by N, P, and S deficiencies, unchanged by K deficiency, and increased by Ca, Mg, and Fe deficiencies. Glutamine synthetase activity closely paralleled nitrate reductase activity and was decreased by deficiencies of N, P, K, Ca, Mg, and S. Glutamic-oxaloacetic transaminase was not sensitive to macronutrient deficiencies. High ¹⁴C-leucine incorporation into tissue sections of N-, P-, K-, Ca-, and S-deficient seedlings did not appear indicative of protein synthesis rates in intact seedlings. Nutritional deficiencies apparently depleted endogenous amino acid pools and caused less inhibition of exogenous ¹⁴C-leucine incorporation into protein.     

Molybdate toxicity in Chinese cabbage is not the direct consequence of changes in sulphur metabolism

• In polluted areas, plants may be exposed to supra‐optimal levels of the micronutrient molybdenum. The physiological basis of molybdenum phytotoxicity is poorly understood. Plants take up molybdenum as molybdate, which is a structural analogue of sulphate. Therefore, it is presumed that elevated molybdate concentrations may hamper the uptake and subsequent metabolism of sulphate, which may induce sulphur deficiency.
• In the current research, Chinese cabbage (Brassica pekinensis) seedlings were exposed to 50, 100, 150 and 200 μm Na₂MoO₄ for 9 days.
• Leaf chlorosis and a decreased plant growth occurred at concentrations ≥100 μm . Root growth was more affected than shoot growth. At ≥100 μm Na₂MoO₄, the sulphate uptake rate and capacity were increased, although only when expressed on a root fresh weight basis. When expressed on a whole plant fresh weight basis, which corrects for the impact of molybdate on the shoot‐to‐root ratio, the sulphate uptake rate and capacity remained unaffected. Molybdate concentrations ≥100 μm altered the mineral nutrient composition of plant tissues, although the levels of sulphur metabolites (sulphate, water‐soluble non‐protein thiols and total sulphur) were not altered. Moreover, the levels of nitrogen metabolites (nitrate, amino acids, proteins and total nitrogen), which are generally strongly affected by sulphate deprivation, were not affected. The root water‐soluble non‐protein thiol content was increased, and the tissue nitrate levels decreased, only at 200 μm Na₂MoO₄.
• Evidently, molybdenum toxicity in Chinese cabbage was not due to the direct interference of molybdate with the uptake and subsequent metabolism of sulphate.

     

Copper-Deficiency in Brassica napus Induces Copper Remobilization,Molybdenum Accumulation and Modification of the Expression of Chloroplastic Proteins

During the last 40 years, crop breeding has strongly increased yields but has had adverse effects on the content of micronutrients, such as Fe, Mg, Zn and Cu, in edible products despite their sufficient supply in most soils. This suggests that micronutrient remobilization to edible tissues has been negatively selected. As a consequence, the aim of this work was to quantify the remobilization of Cu in leaves of Brassica napus L. during Cu deficiency and to identify the main metabolic processes that were affected so that improvements can be achieved in the future. While Cu deficiency reduced oilseed rape growth by less than 19% compared to control plants, Cu content in old leaves decreased by 61.4%, thus demonstrating a remobilization process between leaves. Cu deficiency also triggered an increase in Cu transporter expression in roots (COPT2) and leaves (HMA1), and more surprisingly, the induction of the MOT1 gene encoding a molybdenum transporter associated with a strong increase in molybdenum (Mo) uptake. Proteomic analysis of leaves revealed 33 proteins differentially regulated by Cu deficiency, among which more than half were located in chloroplasts. Eleven differentially expressed proteins are known to require Cu for their synthesis and/or activity. Enzymes that were located directly upstream or downstream of Cu-dependent enzymes were also differentially expressed. The overall results are then discussed in relation to remobilization of Cu, the interaction between Mo and Cu that occurs through the synthesis pathway of Mo cofactor, and finally their putative regulation within the Calvin cycle and the chloroplastic electron transport chain.     

The effect of sodium bicarbonate on plant performance and iron acquisition system of FA-5 (Forner-Alcaide 5) citrus seedlings

This work studies the effect of bicarbonate on plant performance and the iron acquisition system of Forner-Alcaide 5 (FA-5) seedlings, a citrus genotype known for its tolerance to calcareous soils. Plants were irrigated for 6 weeks with or without 10 mM NaHCO₃. Treatment significantly decreased shoot growth, photosynthetic levels and iron concentration in shoots and roots. o,o-⁵⁷FeEDDHA experiments indicated that ⁵⁷Fe uptake by roots was inhibited in treated plants. Moreover, those seedlings accumulated more ⁵⁷Fe in roots, and enhanced mRNA accumulation of ferric reductase genes FRO1 and FRO2 and FC-R activity in roots. H⁺-ATPase activity and HA1 gene expression were also increased, while HA2 was not affected. In addition, expression of the iron transporter gene IRT1 was increased, while IRT2 was not significantly affected. Finally, according to PEPC enzymatic activity, PEPC1 gene expression was higher in treated roots. In conclusion, it appears that bicarbonate prevents medium acidification by roots, thus reducing Fe²⁺ uptake. Accordingly, Fe deficiency enhanced the expression of some genes related with the Fe acquisition system (IRT1, FRO1, FRO2, HA1 and PEPC1) and the activity of the corresponding enzymes, which appear to constitute an adaptive mechanism of FA-5 in these soils.     

The copper-molybdenum antagonism in ruminants. I. The formation of thiomolybdates in animal rumen

The formation of thiomolybdates, MoO_xS_4?x^2?(x = 0, 1, 2, or 3), from molybdate and sulphide salts in aqueous media has been studied under conditions which simulate the fluid phase in the rumen. The influences of the sulphide:molybdenum ratio, pH and phosphate levels on the nature of the species formed were investigated. The thiomolybdates, in particular the MoS_4^2? ion, have been implicated as the active intermediates in the widespread molybdenum induced copper deficiency that affects ruminants. The results presented here show that, under physiological conditions, di- and trithiomolybdates will form more readily than tetrathiomolybdate.     

Bacillus subtilis and Enterobacter cloacae endophytes from healthy Theobroma cacao L. trees can systemically colonize seedlings and promote growth

Clonal genotypes resistant to fungal diseases are an important component of the cocoa production system in southeastern Bahia state (Brazil), so that technologies for faster production of stronger and healthier plantlets are highly desirable. In this study, the effects of inoculated bacterial endophytes isolated from healthy adult cacao plants on seedlings, and aspects related to inoculation methods, colonization patterns, and photosynthesis were investigated. Sequencing of 16S rRNA, hsp-60, and rpo-B genes placed the wild-type isolates within the species Enterobacter cloacae (isolates 341 and 344) and Bacillus subtilis (isolate 629). Spontaneous rifampicin-resistant (rif^R) variants for 344 were also produced and tested. Endophytic application was either by immersion of surface sterilized seeds in bacterial suspensions or direct inoculation into soil, 20 days after planting non-inoculated seeds into pots. Results from in vitro recovery of inoculated isolates showed that the wild-type endophytes and rif^R variants systemically colonized the entire cacao seedlings in 15–20 days, regardless of the inoculation method. Some endophytic treatments showed significant increases in seedlings’ height, number of leaves, and dry matter. Inoculation methods affected the combined application of endophytes, which maintained the growth-promotion effects, but not in the same manner as in single applications. Interestingly, the 344-3.2 rif^R variant showed improved performance in relation to both the wild type and another related variant. Photosynthetic rates and stomatal conductance increased significantly for some endophytic treatments, being partially associated with effects on growth and affected by the inoculation method. The results suggest that E. cloacae and B. subtilis endophytes from healthy adult plants (not transmitted by seeds) were able to promote vegetative growth on cacao seedlings. The development of products for large-scale use in seedlings/plantlets production systems was discussed.     

Haemolysis and Perturbations in the Systemic Iron Metabolism of Suckling,Copper-Deficient Mosaic Mutant Mice – An Animal Model of Menkes Disease

The biological interaction between copper and iron is best exemplified by the decreased activity of multicopper ferroxidases under conditions of copper deficiency that limits the availability of iron for erythropoiesis. However, little is known about how copper deficiency affects iron homeostasis through alteration of the activity of other copper-containing proteins, not directly connected with iron metabolism, such as superoxide dismutase 1 (SOD1). This antioxidant enzyme scavenges the superoxide anion, a reactive oxygen species contributing to the toxicity of iron via the Fenton reaction. Here, we analyzed changes in the systemic iron metabolism using an animal model of Menkes disease: copper-deficient mosaic mutant mice with dysfunction of the ATP7A copper transporter. We found that the erythrocytes of these mutants are copper-deficient, display decreased SOD1 activity/expression and have cell membrane abnormalities. In consequence, the mosaic mice show evidence of haemolysis accompanied by haptoglobin-dependent elimination of haemoglobin (Hb) from the circulation, as well as the induction of haem oxygenase 1 (HO1) in the liver and kidney. Moreover, the hepcidin-ferroportin regulatory axis is strongly affected in mosaic mice. These findings indicate that haemolysis is an additional pathogenic factor in a mouse model of Menkes diseases and provides evidence of a new indirect connection between copper deficiency and iron metabolism.     

Mycorrhization and phosphorus nutrition affect water relations and CAM induction by drought in seedlings of Clusia minor

Background and Aims

Crassulacean acid metabolism (CAM) is currently viewed as an adaptation to water deficit. In plants of Clusia minor, which grow mostly on acidic, P-deficient soils, CAM is induced by water deficit. The symbiosis between plants and mycorrhizal fungi alleviates the symptoms of P deficiency and may influence drought resistance. Therefore, the effect of P supply, modified by three different experimental treatments, on the induction of CAM by drought in C. minor was investigated to test the hypothesis that P deficiency will produce greater CAM activity and, in addition, that treatment will modify drought tolerance.

Methods

Seedlings were grown in forest soil sterilized and inoculated with Scutellospora fulgida (SF treatment), sterilized and supplemented with P (Ph treatment) or non-sterilized and containing native mycorrhizae (Nat treatment). Leaf turgor potential (ψ_T) was determined psychrometrically, and CAM activity as nocturnal acid accumulation (ΔH⁺) by titration of dawn and dusk leaf sap.

Key Results

Plant mass and P content were higher in SF and Ph than in Nat seedlings. After 21 d of water deficit, ψ_T increased in SF, decreased in Ph and remained unchanged in Nat, and, after 7 and 14 d of water deficit, ΔH⁺ in Nat was three times higher than at the beginning of drought, whereas in SF and Ph ΔH⁺ was lower than on day 0.

Conclusions

P deficiency in Nat seedlings was ameliorated by inoculation or P addition. The SF and Nat seedlings showed greater tolerance of drought than Ph. P deficiency promoted the induction of CAM by drought in Nat seedlings, whereas P fertilization and mycorrhization did not. Nocturnal acid accumulation was highly and negatively correlated with plant P and N contents, indicating that P and N deficiencies are promoters of CAM in droughted plants of C. minor.Key words: Clusia minor, crassulacean acid metabolism, CAM, mycorrhiza, drought, phosphorus deficiency, nitrogen–water relations     

Phytochemical analysis of Jatropha curcas L. during different seasons and developmental stages and seedling growth of wheat (Triticum aestivum L) as affected by extracts/leachates of Jatropha curcas L

Jatropha curcas shows invasive characters and is a significant source of many phytochemicals with varying biological activities. Different plant parts of Jatropha curcas L exhibited variation in their phytochemical constituents. Leaves and ovary walls were found to contain higher contents of total phenols, tannins and phytic acid whereas free amino acids were greater in leaves. Young leaves of Jatropha show greater contents of all these metabolites. Further, plants exhibit seasonal differences as leaves collected during summer (May-June) have greater accumulation of total phenols, tannins and free amino acids however, phytic acid was more during rainy season. Leachates and extracts in their higher concentrations adversely affected the germination and growth of wheat seedlings however, lower concentrations were more or less stimulatory. These treatments not only decreased the length, fresh and dry weight of seedlings but also affected the chlorophyll contents and activity of enzymes such as nitrate reductase, aminotransferases in wheat seedlings however, the activity of superoxide dismutase and ascorbate peroxidases increased. Experiments indicate harmful allelopathic effects of Jatropha leachates /extracts on wheat seedlings, hence further experimentation and analysis is recommended before continued plantation of Jatropha particularly on fertile soils. However. Growth of Jatropha plants on saline soils and their potential for accumulating sodium, potassium and chloride are the attributes suggesting the possibility of use of Jatropha plants in improving saline soils.     

Sulfur deprivation and nitrogen metabolism in maize seedlings

The objective of this experiment was to elucidate the manner in which N metabolism is influenced by S nutrition. Maize (Zea mays L.) seedlings supplied with Hoagland solution minus SO₄²⁻ exhibited S deficiency symptoms 12 days after emergence. Prior to development of these symptoms, a decline in leaf blade nitrate reductase (NR, EC 1.6.6.1) activity was observed in S-deprived seedlings compared to normal seedlings. Twelve days after emergence, in vitro NR activity was diminished 50% compared to normal seedlings. Glutamine synthetase (EC 6.3.1.2) and NAD-glutamate dehydrogenase (EC 1.4.1.2) activities were less severely affected (19 and 13%, respectively, at day 12). NADP-glutamate dehydrogenase (EC 1.4.1.4) activity and leaf blade fresh weight were not altered by S deprivation. Concentrations of soluble protein and chlorophyll (a and b) in leaf blades were reduced 18 and 25%, respectively, at day 12. A significantly higher concentration of NO₃⁻-N was observed for leaf blade and stem (culms, leaf sheaths, and unfurled leaves) fractions (46 and 31%, respectively) in S-deprived plants. In contrast to the other parameters measured, NR activity in S-deprived seedlings could be readily restored to the normal level by addition of SO₄²⁻. The apparent preferential effect of S deprivation on NR activity could be causally related to the observed changes in NO₃⁻-N and soluble protein concentration.     

Nutritional control of xanthine dehydrogenase. II. Effects on xanthine dehydrogenase and aldehyde oxidase of culturing wild-type and mutant Drosophila on different levels of molybdenum

Two new mutants, deficient in aldehyde oxidase and xanthine dehydrogenase, have been isolated from a wild-type stock of Drosophila melanogaster and have been provisionally termed lxd ^c and lxd ^d, respectively, as both mutants appear to be allelic with lxd (low xanthine dehydrogenase). An analysis has been made of the effects of dietary molybdenum on lxd, lxd ^c, lxd^d, lao (low aldehyde oxidase), mal (maroon-like eye color), and pac (Pacific) wild-type flies. On the lower dietary levels of 10 ^?3 M and 10 ^?2 M molybdenum, increases in specific activity of both enzymes were observed only in lxd. Furthermore, two- to three-fold increases in specific activity of both enzymes occurred in all strains, except mal, when cultured on 5×10 ^?2 M molybdenum. The lxd and lxd ^c strains failed to survive on this high concentration of the ion. Similar concentrations of molybdenum had no effect in vitro. An extra electrophoretic band of xanthine dehydrogenase was observed on polyacrylamide gel from extracts of wild-type flies cultured on certain levels of molybdenum, but its appearance was not always correlated with the increases in specific activity.     

The Role of Copper Oxide Nanomaterials on Ruta graveolens Physiological Response,and IRT1 and CAT Gene Expression

Background

Copper oxide nanomaterials’ (NMs) are important for the critical roles of Cu as a micronutrient that its improper concentration could cause toxicity or deficiency in plant. The Nano form of CuO could amplify the effects due to special characteristic of nano materials.

Method

Treatments of 0.1, 0.5, and 2.5 μM and NM of copper with three replications were applied to plants under hydroponic conditions. Physiological parameters and expression of IRT1 and CAT genes were investigated.

Results

Copper absorption decreased according to MMs-CuO ? NMs-CuO ?? CuSO4 pattern. The positive effects of MMs-CuO on plant copper content were higher than those of nanomaterials and CuSO4. MMs-CuO effect was more significant on plant biomass increase compared to the control. Rue plant needed lower amounts of copper for better plant growth. The treatments increased protein and carotenoids content in leaves compared with control. Changes in total chlorophyll content under three copper forms were very low and were only increased in leaves at 0.1 μM CuSO4. The NMs-CuO and MMs-CuO similarly reduced leaves’ Cu, MDA and ROS contents, and SOD activities. CAT enzyme activity had a similar pattern in three copper forms. CAT enzyme activity was only induced under the lowest level of three forms, while at other levels of Cu, it was reduced. NMs-CuO had a more negative effect on IRT1 relative gene expression in root compared with other iron forms. The IRT1 relative gene expression in shoots was positively affected under 2.5 μM CuSO4, 0.5 μM MMs-CuO, and 0.1 and 2.5 μM NMs CuO treatments.

Conclusion

The effect of micro- and nano-CuO on physiology and gene expression mechanisms in rue plants is shown to be does-dependent.

     

Zinc improves salt tolerance by increasing reactive oxygen species scavenging and reducing Na+ accumulation in wheat seedlings

Salt decreases the uptake of Zn and other minerals and causes nutritional disorders in plants. Zn is an essential micronutrient for all organisms and it is reasonable to hypothesize that Zn status is essential for maintaining salt tolerance in plants. In this study, the physiological and molecular mechanisms of Zn-based alleviation of salt stress in wheat seedlings were investigated. Our results indicate that sufficient Zn nutrition maintained antioxidative enzyme activities and decreased a reactive oxygen species over-accumulation in wheat seedlings. Our data also reveal that sufficient Zn nutrition improved the expression of Na⁺/H⁺ antiporter genes, TaSOS1 and TaNHX1, thereby decreasing the Na⁺ accumulation and subsequently improving salt tolerance in wheat seedlings.     

Effects of Potassium Nutrition on Ribonucleic Acid and Ribonuclease in Zea mays L

Potassium deficiency decreased the total RNA per shoot in corn (Zea mays L.) seedlings due to the reduced sizes of the plant, but increased the ratio of RNA to dry matter as much as 40%. Total base composition of RNA was unaffected by K⁺ deficiency. Thus K⁺ deficiency does not appear to alter RNA metabolism to such an extent that a lack of RNA becomes a factor limiting growth. The RNA contents of leaves were followed as deficiency developed or as the plant recovered from deficiency. Such time-course studies, although extremely useful in microbial work, did not yield as much information with higher plants. The ratio of RNA to dry matter in younger leaves was much higher than that in older leaves. The ribonuclease level in corn shoots was increased as much as threefold by K⁺ deficiency.     

Stimulation of root acid phosphatase by phosphorus deficiency is regulated by ethylene in Medicago falcata

Plants have developed numerous strategies to cope with phosphorus (P) deficiency resulting from low availability in soils. Evolution of ethylene and up-regulation of root secreted acid phosphatase activity are common for plants in response to P deficiency. To determine the role of ethylene in response of plants to P deficiency, we investigated the effects of ethylene precursor (1-amino cyclopropane-1-carboxylic acid, ACC) and ethylene synthesis antagonists (aminoethoxyvinylglycine AVG, cobalt, Co²⁺) on P concentrations in roots and shoots of Medicago falcata seedlings grown in P-sufficient (500 μM H₂PO₄⁻) and P-deficient (5 μM H₂PO₄⁻) solution. After transferring M. falcata seedlings from P-sufficient to P-deficient solution for 2 days, root P concentration was significantly reduced. The reduction in root P concentration was reversed by AVG and Co²⁺, and a similar reduction in root P concentration of seedlings exposed to P-sufficient solution was observed by ACC. Expression of high-affinity phosphate transporters (MfPT1, MfPT5) was enhanced by P-deficiency and this process was reversed by AVG and Co²⁺. There was a marked increase in activity of root acid phosphatase (APase) and expression of gene encoding APase (MfPAP1) under P-deficient conditions, and the increase in APAse activity and expression of MfPAP1 was inhibited by AVG and Co²⁺. APase activity and expression of MfPAP1 expression in seedlings grown in P-sufficient solution were enhanced by ACC. Root and shoot P concentrations were increased when organic phosphorus was added to the P-deficient solution, and the increase in P concentration was significantly inhibited by AVG and Co²⁺. These results indicate that ethylene plays an important role in modulation of P acquisition by possibly mobilizing organic P via up-regulating root APase activity and high-affinity phosphate transporters.     

Kaurene Synthetase Activity in Helianthus annuus L. : Increases in Enzyme Activity after Storage of Seedlings in Liquid Nitrogen

In previous studies, the conversion of geranylgeranyl pyrophosphate to ent-kaurene (kaurene synthetase AB activity) could not be detected readily in crude extracts of sunflower (Helianthus annuus L.) seedlings (Shen-Miller, West 1982 Plant Physiol 69: 637-641). These investigations also revealed the presence of inhibitors for Marah macrocarpus kaurene synthetase AB activity in crude extracts of sunflower seedlings. It has now been found that crude extracts prepared from intact sunflower seedlings stored in liquid N₂ for several days have greatly enhanced AB activity in comparison with frozen, but not stored, controls. The levels of activity for the conversion of copalyl pyrophosphate to ent-kaurene (kaurene synthetase B activity) are affected only slightly by storage of intact seedlings in liquid N₂. Extracts from intact seedlings that had been stored in liquid N₂ also showed less inhibitory activity for Marah macrocarpus endosperm kaurene synthetase AB activity.