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1.
Proc Natl Acad Sci U S A ; 108(16): 6399-404, 2011 Apr 19.
Artigo em Inglês | MEDLINE | ID: mdl-21444818

RESUMO

China and other rapidly developing economies face the dual challenge of substantially increasing yields of cereal grains while at the same time reducing the very substantial environmental impacts of intensive agriculture. We used a model-driven integrated soil-crop system management approach to develop a maize production system that achieved mean maize yields of 13.0 t ha(-1) on 66 on-farm experimental plots--nearly twice the yield of current farmers' practices--with no increase in N fertilizer use. Such integrated soil-crop system management systems represent a priority for agricultural research and implementation, especially in rapidly growing economies.


Assuntos
Agricultura/métodos , Produtos Agrícolas/crescimento & desenvolvimento , Abastecimento de Alimentos , Solo , Zea mays/crescimento & desenvolvimento , Agricultura/economia , China , Produtos Agrícolas/economia , Fertilizantes/economia
2.
J Exp Bot ; 63(7): 2411-20, 2012 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-22249995

RESUMO

This work was focused on the role of silicon (Si) in amelioration of manganese (Mn) toxicity caused by elevated production of hydroxyl radicals (·OH) in the leaf apoplast of cucumber (Cucumis sativus L.). The plants were grown in nutrient solutions with adequate (0.5 µM) or excessive (100 µM) Mn concentrations with or without Si being supplied. The symptoms of Mn toxicity were absent in the leaves of Si-treated plants subjected to excess Mn, although the leaf Mn concentration remained extremely high. The apoplastic concentration of free Mn(2+) and H(2)O(2) of high Mn-treated plants was significantly decreased by Si treatment. Si supply suppressed the Mn-induced increased abundance of peroxidase (POD) isoforms in the leaf apoplastic fluid, and led to a rapid suppression of guaiacol-POD activity under excess Mn. The spin-trapping reagent 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline-N-oxide was used to detect ·OH by electron paramagnetic resonance spectroscopy. Although supplying Si markedly decreased the accumulation of ·OH in the leaf apoplast with excess Mn, adding monosilicic acid to the Mn(2+)/H(2)O(2) reaction mixture did not directly affect the Fenton reaction in vitro. The results indicate that Si contributes indirectly to a decrease in ·OH in the leaf apoplast by decreasing the free apoplastic Mn(2+), thus regulating the Fenton reaction. A direct inhibitory effect of Si on guaiacol-POD activity (demonstrated in vitro) may also contribute to decreasing the POD-mediated generation of ·OH.


Assuntos
Cucumis sativus/metabolismo , Radical Hidroxila/metabolismo , Manganês/toxicidade , Folhas de Planta/metabolismo , Silício/farmacologia , Cucumis sativus/efeitos dos fármacos , Peróxido de Hidrogênio/metabolismo , Folhas de Planta/efeitos dos fármacos
3.
Physiol Plant ; 142(3): 287-96, 2011 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-21338370

RESUMO

Root release of phytosiderophores (PSs) is an important step in iron (Fe) acquisition of grasses, and this adaptive reaction of plants is affected by various plant and environmental factors. The objectives of this study were to study the effects of varied nitrogen (N) supply on (1) root and leaf concentrations of methionine, a precursor in the PS biosynthesis, (2) PS release from roots, (3) mobilization and uptake of Fe from (59) Fe-labeled Fe(III)-hydroxide [(59) Fe(OH)(3) ] and (4) root uptake of (59) Fe-labeled Fe(III)-deoxymugineic acid (DMA) by durum wheat (Triticum durum, cv. Balcali2000) plants grown in a nutrient solution. Enhanced N supply from 0.5 to 6 mM in a nutrient solution significantly increased the root release of PS under Fe deficiency. High N supply was also highly effective in increasing mobilization and root uptake of Fe from (59) Fe-hydroxide under low Fe supply. With adequate Fe, N nutrition did not affect mobilization and uptake of Fe from (59) Fe(OH)(3) . Root uptake and shoot translocation of Fe supplied as (59) Fe(III)-DMA were also stimulated by increasing N supply. Leaf concentration of methionine was reduced by low Fe supply, and this decline was pronounced in high N plants. The results show that the root release of PS, mobilization of Fe from (59) Fe(OH)(3) and root uptake and shoot translocation of Fe(III)-PS by durum wheat are markedly affected by N nutritional status of plants. These positive N effects may have important implications for Fe nutrition of human populations and should be considered in biofortification of food crops with Fe.


Assuntos
Deficiências de Ferro , Ferro/metabolismo , Nitrogênio/farmacologia , Raízes de Plantas/metabolismo , Sideróforos/metabolismo , Triticum/efeitos dos fármacos , Triticum/metabolismo , Biomassa , Ácido Edético/farmacologia , Compostos Férricos/farmacologia , Metionina/metabolismo , Nitrogênio/metabolismo , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/crescimento & desenvolvimento , Brotos de Planta/efeitos dos fármacos , Brotos de Planta/crescimento & desenvolvimento , Brotos de Planta/metabolismo , Triticum/crescimento & desenvolvimento
4.
Mycorrhiza ; 20(1): 13-23, 2009 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-19499252

RESUMO

Sweet potato plants were grown with or without Glomus intraradices in split-root pots with adjacent root compartments containing a soil with a low availability of phosphate. One fungal tube, from which root growth was excluded, was inserted into each root compartment. During 4 weeks before harvest, the soil moisture level in either both or only one of the two root-compartments of each pot was decreased. Controls remained well watered. Low soil moisture generally had a negative effect on the amount of extraradical mycelium of G. intraradices extracted from the fungal tubes. Sporulation in the fungal tubes was much higher compared with the soil in the root compartment, but remained unaffected by the soil moisture regime. Concentrations of P in extraradical mycelium were much lower than usually found in plants and fungi, while P concentrations in associated mycorrhizal host plant tissues were in an optimum range. This suggests efficient transfer of P from the extraradical mycelium to the host plant. Despite the negative effect of a low soil moisture regime on extraradical G. intraradices development, the symbiosis indeed contributed significantly to P uptake of plants exposed to partial rootzone drying. The possibility that extraradical arbuscular mycorrhizal fungal development was limited by P availability under dry soil conditions is discussed.


Assuntos
Glomeromycota , Ipomoea batatas/crescimento & desenvolvimento , Micélio/crescimento & desenvolvimento , Micorrizas , Raízes de Plantas , Simbiose , Secas , Glomeromycota/crescimento & desenvolvimento , Glomeromycota/metabolismo , Ipomoea batatas/microbiologia , Micorrizas/crescimento & desenvolvimento , Micorrizas/metabolismo , Fosfatos/metabolismo , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/microbiologia , Solo/análise , Água/análise
5.
J Agric Food Chem ; 54(26): 10019-25, 2006 Dec 27.
Artigo em Inglês | MEDLINE | ID: mdl-17177536

RESUMO

Evidence clearly shows that cationic micronutrients in spray solutions reduce the herbicidal effectiveness of glyphosate for weed control due to the formation of metal-glyphosate complexes. The formation of these glyphosate-metal complexes in plant tissue may also impair micronutrient nutrition of nontarget plants when exposed to glyphosate drift or glyphosate residues in soil. In the present study, the effects of simulated glyphosate drift on plant growth and uptake, translocation, and accumulation (tissue concentration) of iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) were investigated in sunflower (Helianthus annuus L.) plants grown in nutrient solution under controlled environmental conditions. Glyphosate was sprayed on plant shoots at different rates between 1.25 and 6.0% of the recommended dosage (i.e., 0.39 and 1.89 mM glyphosate isopropylamine salt). Glyphosate applications significantly decreased root and shoot dry matter production and chlorophyll concentrations of young leaves and shoot tips. The basal parts of the youngest leaves and shoot tips were severely chlorotic. These effects became apparent within 48 h after the glyphosate spray. Glyphosate also caused substantial decreases in leaf concentration of Fe and Mn while the concentration of Zn and Cu was less affected. In short-term uptake experiments with radiolabeled Fe (59Fe), Mn (54Mn), and Zn (65Zn), root uptake of 59Fe and 54Mn was significantly reduced in 12 and 24 h after application of 6% of the recommended dosage of glyphosate, respectively. Glyphosate resulted in almost complete inhibition of root-to-shoot translocation of 59Fe within 12 h and 54Mn within 24 h after application. These results suggest that glyphosate residues or drift may result in severe impairments in Fe and Mn nutrition of nontarget plants, possibly due to the formation of poorly soluble glyphosate-metal complexes in plant tissues and/or rhizosphere interactions.


Assuntos
Glicina/análogos & derivados , Helianthus/efeitos dos fármacos , Ferro/metabolismo , Manganês/metabolismo , Folhas de Planta/efeitos dos fármacos , Transporte Biológico/efeitos dos fármacos , Glicina/administração & dosagem , Helianthus/metabolismo , Radioisótopos de Ferro , Folhas de Planta/metabolismo , Radioisótopos , Glifosato
6.
J Plant Physiol ; 163(6): 591-600, 2006 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-16330125

RESUMO

It has previously been shown that boron (B) deficiency inhibits growth of the plant apex, which consequently results in a relatively weak apical dominance, and a subsequent sprouting of lateral buds. Auxin and cytokinins (CKs) are the two most important phytohormones involved in the regulation of apical dominance. In this study, the possible involvement of these two hormones in B-deficiency-induced changes in apical dominance was investigated by applying B or the synthetic CK CPPU to the shoot apex of pea plants grown in nutrient solution without B supply. Export of IAA out of the shoot apex, as well as the level of IAA, Z/ZR and isopentenyl-adenine/isopentenyl-adenosine (i-Ade/i-Ado) in the shoot apex were assayed. In addition, polar IAA transport capacity was measured in two internodes of different ages using 3H-IAA. In B-deficient plants, both the level of auxin and CKs were reduced, and the export of auxin from the shoot apex was considerably decreased relative to plants well supplied with B. Application of B to the shoot apex restored the endogenous Z/ZR and IAA level to control levels and increased the export of IAA from the shoot apex, as well as the 3H-IAA transport capacity in the newly developed internodes. Further, B application to the shoot apex inhibited lateral bud growth and stimulated lateral root formation, presumably by stimulated polar IAA transport. Applying CPPU to the shoot apex, a treatment that stimulates IAA export under adequate B supply, considerably reduced the endogenous Z/ZR concentration in the shoot apex, but had no stimulatory effect on IAA concentration and transport in B-deficient plants. A similar situation appeared to exist in lateral buds of B-deficient plants as, in contrast to plants well supplied with B, application of CKs to these plants did not stimulate lateral bud growth. In contrast to the changes of Z/ZR levels in the shoot apex, which occurred after application of B or CPPU, the levels of i-Ade/i-Ado stayed more or less constant. These results suggest that there is a complex interaction between B supply and plant hormones, with a B-deficiency-induced inhibition of IAA export from the shoot apex as one of the earliest measurable events.


Assuntos
Boro/fisiologia , Citocininas/fisiologia , Ácidos Indolacéticos/metabolismo , Pisum sativum/crescimento & desenvolvimento , Brotos de Planta/crescimento & desenvolvimento , Giberelinas/fisiologia , Compostos de Fenilureia , Raízes de Plantas/crescimento & desenvolvimento , Piridinas , Trítio
7.
J Environ Qual ; 34(6): 2157-66, 2005.
Artigo em Inglês | MEDLINE | ID: mdl-16275716

RESUMO

White lupine (Lupinus albus L.) was used as a phosphorus (P)-efficient model plant to study the effects of elevated atmospheric CO(2) concentrations on (i) P acquisition, (ii) the related alterations in root development and rhizosphere chemistry, and (iii) the functional and structural diversity of rhizosphere microbial communities, on a P-deficient calcareous subsoil with and without soluble P fertilization. In both +P (80 mg P kg(-1)) and -P treatments (no added P), elevated CO(2) (800 micromol mol(-1)) increased shoot biomass production by 20 to 35% and accelerated the development of cluster roots, which exhibit important functions in chemical mobilization of sparingly soluble soil P sources. Accordingly, cluster root formation was stimulated in plants without P application by 140 and 60% for ambient and elevated CO(2) treatments, respectively. Intense accumulation of citrate and increased activities of acid and alkaline phosphatases, but also of chitinase, in the rhizosphere were mainly confined to later stages of cluster root development in -P treatments. Regardless of atmospheric CO(2) concentrations, there was no significant effect on accumulation of citrate or on selected enzyme activities of C, N, and P cycles in the rhizosphere of individual root clusters. Discriminant analysis of selected enzyme activities revealed that mainly phosphatase and chitinase contributed to the experimental variance (81.3%) of the data. Phosphatase and chitinase activities in the rhizosphere might be dominated by the secretion from cluster roots rather than by microbial activity. Alterations in rhizosphere bacterial communities analyzed by denaturing gradient gel electrophoresis (DGGE) were related with the intense changes in root secretory activity observed during cluster root development but not with elevated CO(2) concentrations.


Assuntos
Lupinus/metabolismo , Lupinus/microbiologia , Micorrizas/metabolismo , Fósforo/metabolismo , Raízes de Plantas/microbiologia , Atmosfera , Carbono/metabolismo , Dióxido de Carbono , Citratos/análise , Citratos/metabolismo , Enzimas/metabolismo , Lupinus/crescimento & desenvolvimento , Nitrogênio/metabolismo , Microbiologia do Solo
8.
New Phytol ; 130(4): 511-521, 1995 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-33874479

RESUMO

Graminaceous plant species respond to iron (Fe)-deficiency stress by enhancing the release of phytosiderophores from the roots and the uptake of Fe-phytosiderophores. For studying the mobilization and uptake of apoplasmic root Fe by barley (inherently high phytosiderophore release) and sorghum (inherently low phytosiderophore release) in axenic and nonaxenic (inoculated) nutrient solution, Fe pools in the root apoplasm were loaded during plant preculture with 10-4 M Fe(III)-EDTA. After 27 d growth in Fe-deficient nutrient solution, inoculated barley plants developed moderate Fe-deficiency chlorosis compared with the less chlorotic axenic plants. In inoculated plants, recovery of phytosiderophores and mobilization of apoplasmic root Fe tended to be slightly lower than in axenic plants, and in both treatments apoplasmic root Fe was completely depleted at harvest. As determined by the nonsoluble Fe fraction (> 0·2 µm) in the nutrient solution and at the rhizoplane, the microbial uptake and immobilization of apoplasmic root Fe was estimated at about 3% of the total amount of apoplasmic root Fe after preculture and at less than 10% of plant Fe uptake. Under axenic conditions, Fe-deficient sorghum also depleted apoplasmic root Fe and developed moderate Fe-deficiency chlorosis, although phytosiderophore recovery was 5-10-fold lower than in barley. By contrast, in inoculated sorghum plants, phytosiderophore recovery and Fe mobilization were extremely low. At harvest, in inoculated sorghum plants apoplasmic Fe pools were still considerably loaded and plant Fe uptake was c. 60% lower than that of axenic plants, resulting in severe Fe-deficiency chlorosis. Thus, in Fe-deficient sorghum plants, the lower rate of phytosiderophore release and its degradation restricted an efficient mobilization of apoplasmic root Fe in the presence of micro-organisms. In barley, however, the higher rate of phytosiderophore release allowed a complete mobilization of apoplasmic root Fe even in inoculated nutrient solution. Furthermore, the results show that the dominating effect of micro-organisms in their competition with barley and sorghum for apoplasmic root Fe is the degradation of phytosiderophores rather than the immobilization or uptake of Fe.

9.
Physiol Plant ; 113(3): 346-351, 2001 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-12060279

RESUMO

The intracellular compartmentation of boron (B) in roots of sunflower plants precultured with 100 &mgr;M B (high B) or 1 &mgr;M B (low B) was studied using two independent approaches. In the first approach, short-term efflux studies using the stable isotopes 11B and 10B were carried out. In roots of high B plants, the calculated concentrations of B (nmol gFW -1) were 52.6 in the cell wall, 7.5 in the vacuole, 27.1 in the cytosol and 48.0 in the free space. In roots of low B plants, the concentrations of B (nmol gFW -1) were 43.4 in the cell wall, 2.8 in the vacuole, 17.9 in the cytosol and almost zero in the free space. Although the B supply differed by a factor 100, the B concentrations in the cytosol and the vacuole of low B plants were 66 and 37% of the respective concentrations in high B plants. This suggests an additional role for B in plant metabolism, besides its function in the cell wall. In the second approach, root B pools (cell sap and water-insoluble residue) were determined for comparison, and found to be in good agreement with the results from the efflux study.

10.
Sci Total Environ ; 291(1-3): 45-57, 2002 May 27.
Artigo em Inglês | MEDLINE | ID: mdl-12150442

RESUMO

The use of municipal solid waste (MSW) compost as fertilizer may cause increased leaching due to its high content of trace metals and thus pose a threat to groundwater quality. The effect of MSW compost application on trace metal leaching in calcareous soils has been studied in soil column experiments under laboratory conditions using three soils from the study area in the Gaza Strip and Israel. Higher levels of organic matter in solution (TOMS), nitrate, and the trace metals Cu, Ni and Zn were found in the leachates of a sandy soil and, to a lesser extent, a loamy soil, to which MSW compost had been applied at a rate of 65 Mg ha(-1) (dry weight basis). Nevertheless, the majority of water-soluble trace metal species from compost accumulated in the topsoil rather than washing out, with the exception of aqueous Ni species. Ni concentrations exceeded the maximum allowable limits for drinking water (in Germany: 50 microg l(-1)) at peak times in the leachates from sandy soil, while all other trace metals remained far below the corresponding limits. The highest absolute concentrations of trace metals were found for the leaching of Cu from compost-amended sandy soil (100 microg l(-1)). For Cd, Pb and Hg no evidence of downward movement was found in any assay. Gel filtration studies of the collected soil leachates showed that all trace metals encountered in the leachates existed mostly as organic complexes. In sandy soil most of the water-soluble organic matter added with the compost had leached from the rootzone after a year's equivalent of rainfall, while TOMS mobility was greatly reduced in the loamy soil. The makeup of the TOMS in the sandy soil and its metal-binding capacity was strongly influenced by compost-derived dissolved organic matter (DOM) as observed by FTIR spectrometry. Hence the vertical displacement of trace metals (Cu, Ni, Zn) in these calcareous soils seemed to result primarily from the presence of mobile metal-organic complexes in the soil solution after compost addition. Further studies are required to validate these findings in the field, especially to assess the risk of Cu and Ni leaching in sandy soil.


Assuntos
Metais Pesados/química , Compostos Orgânicos/química , Eliminação de Resíduos/métodos , Gerenciamento de Resíduos/métodos , Compostos de Cálcio/química , Metais Pesados/análise , Compostos Orgânicos/análise , Solo/análise , Poluentes do Solo/análise , Solubilidade
11.
Environ Toxicol Chem ; 21(9): 1775-82, 2002 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-12206415

RESUMO

Municipal solid waste (MSW) composts carry high amounts of trace metals and organic complexing agents that may influence metal bioavailability and mobility after application to soils. In order to assess the degree of organic complexation of trace metals in the solution phase of MSW compost and the relevance of organic ligand type, size exclusion chromatography (SEC) was applied to compost-extracted organic ligands. Adjustment of the elution conditions minimized the interaction with the gel matrix for compost humic substances and dissolved organic matter (DOM) fractions. The SEC was then used to separate the aqueous compost extract into samples with distinct differences in chemical constituents. The highest quantities of Cu, Zn, Ni, Mn, and Cd were found to coelute with the main peak of the SEC elution curve, which, as observed by Fourier-transformed infrared (FTIR) spectroscopy, also had the highest density of carboxyl groups. The ratio of aromatic to aliphatic structures was higher for eluates with low retention times, and cations such as Al, Cr, and Fe were preferably associated with these larger organic molecules. All trace metals in the compost solution phase were bound mostly to DOM rather than forming inorganic complexes.


Assuntos
Metais Pesados/química , Eliminação de Resíduos , Disponibilidade Biológica , Cromatografia em Gel , Ligantes , Metais Pesados/análise , Compostos Orgânicos , Solubilidade , Espectroscopia de Infravermelho com Transformada de Fourier
12.
J Environ Qual ; 31(6): 1885-92, 2002.
Artigo em Inglês | MEDLINE | ID: mdl-12469838

RESUMO

The agricultural practice of amending soils with composted municipal solid waste (MSW) adds significant amounts of organic matter and trace metals, including Cd. Under these conditions, soluble organic complexes of Cd formed in the compost may be more significant than previously thought, due to Cd bioavailability and mobility in the soil environment. To study the relative importance of different types of organic ligands in MSW compost for the binding of Cd, six fractions of the dissolved organic matter (DOM) in addition to humic acid (HA) and fulvic acid (FA) were extracted and their complexation of Cd quantified at pH 7 using an ion-selective electrode (ISE). The highest complexing capacities (CC) for Cd were found for the most humified ligands: HA (2386 micromol Cd g(-1) C of ligand), predialyzed FA (2468 micromol Cd g(-1) C), and HoA, a fulvic-type, easily soluble fraction (1042 micromol Cd g(-1) C). The differences in CC for Cd of the various organic ligands were not directly related to total acid-titratable or carboxylic groups, indicating the importance of sterical issues and other functional groups. The strength of association between Cd and the organic ligands was characterized by calculating stability constants for binding at the strongest sites (pK(int)) and modeling the distribution of binding site strengths. The pK(int) values of the DOM fractions ranged between 6.93 (HiN: polysaccharides) and 8.11 (HiB: proteins and aminosugars), compared with 10.05 for HA and 7.98 for FA. Hence, the highly complex and only partially soluble organic molecules from compost such as HA and FA demonstrated the highest capacity to sequester Cd. However, strong Cd binding of organic ligands containing N-functional groups (HiB) in addition to a high CC of soluble, humified ligands like HoA indicated the relevance of these fractions for the organic complexation of Cd in solution.


Assuntos
Cádmio/química , Substâncias Húmicas/química , Eliminação de Resíduos , Poluentes do Solo/análise , Disponibilidade Biológica , Cádmio/análise , Conservação dos Recursos Naturais , Ligantes , Compostos Orgânicos , Solubilidade
13.
Plant Physiol Biochem ; 56: 14-23, 2012 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-22579940

RESUMO

Soil-less cultivation of horticultural crops represents a fairly recent innovation to traditional agriculture which has several advantages including higher water-use efficiency. When plants are grown with this system, their roots come in contact with nutrients solely via the hydroponic solution. Although its beneficial effects have been widely demonstrated, silicon (Si) is mostly omitted from the composition of nutrient solutions. Therefore, the objective of this study was to assess the beneficial effect of Si addition to hydroponic solution on quali-quantitative aspects of edible production of two cultivars of corn salad (Valerianella locusta (L.) Laterr.) grown in soil-less floating system. Impacts on shelf life of this food were also studied. Results show that the supply of Si increased the edible yield and the quality level reducing the nitrate concentration in edible tissues. This result might be attributed to changes either in the metabolism (such as the nitrate assimilation process) or to the functionality of root mechanisms involved in the nutrient acquisition from the outer medium. In fact, our results show for the first time the ability of Si to modulate the root activity of nitrate and Fe uptake through, at least in part, a regulation of gene expression levels of the proteins involved in this phenomenon. In addition, the presence of Si decreased the levels of polyphenoloxidase gene expression at harvest and, in post-harvest, slowed down the chlorophyll degradation delaying leaf senescence and thus prolonging the shelf life of these edible tissues. In conclusion, data showed that the addition of Si to the nutrient solution can be a useful tool for improving quali-quantitatively the yield of baby leaf vegetable corn salad as well as its shelf life. Since the amelioration due to the Si has been achieved only with one cultivar, the recommendation of its inclusion in the nutrient solution does not exclude the identification of cultivars suitable for this cultivation system and the comprehension of agronomical and environmental factors which could limit the Si benefits.


Assuntos
Biomassa , Regulação da Expressão Gênica de Plantas , Hidroponia/métodos , Ferro/metabolismo , Nitratos/metabolismo , Silício/metabolismo , Valerianella/fisiologia , Catecol Oxidase/genética , Catecol Oxidase/metabolismo , Senescência Celular , Clorofila/metabolismo , Dieta , Fertilizantes , Conservação de Alimentos , Folhas de Planta/crescimento & desenvolvimento , Folhas de Planta/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Raízes de Plantas/metabolismo , Plantas Comestíveis
14.
Plant Physiol Biochem ; 49(5): 489-93, 2011 May.
Artigo em Inglês | MEDLINE | ID: mdl-21486699

RESUMO

As long as 130 years ago Rissmüller reported substantial retranslocation of iron (Fe) from beech leaves (Fagus sylvatica L.) shortly before leaf fall. This rather limited report on Fe retranslocation via the phloem in plants was the reason for this research to study changes in Fe content in individual beech leaves in more detail during the vegetative period. Besides Fe, other micronutrients and particularly Ca and K, well known to differ substantially in phloem mobility, were analysed as mineral nutrient markers. In addition to beech, other deciduous and evergreen species of Angiosperms and Gymnosperms were also studied. As expected, there was no evidence of Ca retranslocation from senescent leaves, while K as a phloem mobile mineral nutrient was retranslocated in fall in deciduous but not in evergreen trees. There was no indication to support Rissmüller's finding of Fe retranslocation in any of the different species studied. From these results, we conclude that natural leaf senescence of trees during late season does not induce retranslocation of Fe and other micronutrients. Possible reasons for the absence of a distinct retranslocation of Fe in the species studied during late season senescence are the lack of a sink activity, as for example the development of seeds in annual plant species (e.g., cereals), or the presence of a root system still active enough to provide Fe and other mineral nutrients for plant demand, and both factors have to be considered in further studies. Reviewing the data in the literature on Fe and Zn retranslocation during senescence, we conclude that in principle both micronutrients are potentially phloem mobile. However, various prerequisites are needed for the occurrence of phloem mobility which were absent in the plant species studied. Regardless of this conclusion, we recommend that in general early published research data need a critical re-evaluation.


Assuntos
Fagus/metabolismo , Ferro/metabolismo , Floema/metabolismo , Folhas de Planta/metabolismo , Chuva Ácida , Boro/análise , Boro/metabolismo , Cálcio/análise , Cálcio/metabolismo , Cobre/análise , Cobre/metabolismo , Cycadopsida/química , Cycadopsida/crescimento & desenvolvimento , Cycadopsida/metabolismo , Fagus/química , Fagus/crescimento & desenvolvimento , Ferro/análise , Folhas de Planta/química , Folhas de Planta/crescimento & desenvolvimento , Potássio/análise , Potássio/metabolismo , Estações do Ano , Silício/análise , Silício/metabolismo , Zinco/análise , Zinco/metabolismo
15.
Plant Physiol Biochem ; 49(5): 506-12, 2011 May.
Artigo em Inglês | MEDLINE | ID: mdl-21236691

RESUMO

Main components of Strategy II mechanism for Fe uptake are secretion of chelating compounds, phytosiderophores, and specific uptake of Fe(III)-phytosiderophores complex. Since the amount of phytosiderophores secreted correlates positively with plant ability to cope with Fe shortage, a role of root hairs in enhancing root capability to store phytosiderophores under Fe stress might be envisaged. In this study the root-hairless mutant of barley (Hordeum vulgare L.) brb (bald root barley) and the wild-type genotype (cv. Pallas) were compared with respect to their capacity to respond to Fe shortage in nutrient solution. Plants were grown with Fe(III)-EDTA at 0, 0.02 and 0.08 mM, in order to reproduce severe or moderate Fe deficiency, and adequate Fe nutritional status, respectively. Analysis was performed after 11 and 14 days considering leaf Fe content, phytosiderophores release and accumulation in root tips, and 59Fe uptake. Biomass accumulation and chlorophyll content were not reduced in mutant plants as compared to wild-type ones; leaf Fe content was similar in both genotypes after 14 days of growth. Accumulation and release of phytosiderophores showed a similar trend in both genotypes when subjected to Fe limitation. Furthermore, no significant difference between the two genotypes was observed when 59Fe uptake was measured. Results seem to support the idea that the presence of root hairs and their increased production in response to low-Fe availability, while causing major modifications of root geometry, did not necessarily lead neither to an effect on growth nor on Fe uptake and accumulation in barley plants.


Assuntos
Hordeum/metabolismo , Ferro/metabolismo , Exsudatos de Plantas/química , Folhas de Planta/metabolismo , Raízes de Plantas/metabolismo , Biomassa , Clorofila/análise , Genótipo , Hordeum/genética , Hordeum/crescimento & desenvolvimento , Ferro/análise , Quelantes de Ferro/metabolismo , Manganês/análise , Manganês/metabolismo , Mutação , Fosfatos/metabolismo , Raízes de Plantas/crescimento & desenvolvimento , Sideróforos/metabolismo , Zinco/análise , Zinco/metabolismo
16.
Environ Pollut ; 159(2): 408-15, 2011 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-21093133

RESUMO

The role of root hairs in Cd acquisition from soil was investigated in three pot experiments using a root hairless mutant (bald root barley, brb) and its wild-type (WT) cultivar of barley (Hordeum vulgare). brb had significantly lower concentrations and lower total amounts of Cd in shoots than WT. The Cd uptake efficiency based on total root length was 8-45% lower in brb than in WT. The difference between brb and WT increased with increasing extractable Cd in soil under the experimental conditions used. Additions of phosphate to soil decreased Cd extractability. Both soil and foliar additions of phosphate decreased root length, and root hair formation in WT. These effects resulted in decreased Cd uptake with increasing P supply. Cd uptake in WT correlated significantly with root length, root hair length and density, and soil extractable Cd. Root hairs contribute significantly to Cd uptake by barley.


Assuntos
Cádmio/metabolismo , Hordeum/metabolismo , Raízes de Plantas/metabolismo , Poluentes do Solo/metabolismo , Hordeum/genética , Hordeum/crescimento & desenvolvimento , Fosfatos/metabolismo , Raízes de Plantas/genética , Raízes de Plantas/crescimento & desenvolvimento
17.
Environ Pollut ; 159(4): 1007-16, 2011 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-21251741

RESUMO

An automated system for continuous measurement of N2O fluxes on an hourly basis was employed to study N2O emissions in an intensively managed low carbon calcareous soil under sub-humid temperate monsoon conditions. N2O emissions occurred mainly within two weeks of application of NH4(+) based fertilizer and total N2O emissions in wheat (average 0.35 or 0.21 kg N ha⁻¹ season⁻¹) and maize (average 1.47 or 0.49 kg N ha⁻¹ season⁻¹) under conventional and optimum N fertilization (300 and 50-122 kg N ha⁻¹, respectively) were lower than previously reported from low frequency measurements. Results from closed static chamber showed that N2O was produced mainly from nitrification of NH4(+)-based fertilizer, with little denitrification occurring due to limited readily oxidizable carbon and low soil moisture despite consistently high soil nitrate-N concentrations. Significant reductions in N2O emissions can be achieved by optimizing fertilizer N rates, using nitrification inhibitors, or changing from NH4(+)- to NO3(-)-based fertilizers.


Assuntos
Fertilizantes , Óxido Nitroso/análise , Compostos de Amônio Quaternário/metabolismo , Triticum/metabolismo , Zea mays/metabolismo , Agricultura/métodos , Poluição do Ar/análise , Poluição do Ar/prevenção & controle , Carbono/metabolismo , China , Desnitrificação , Monitoramento Ambiental , Nitrificação , Solo/química , Tempo (Meteorologia)
18.
Funct Plant Biol ; 34(12): 1130-1136, 2008 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32689443

RESUMO

The objective of this research was to test the hypothesis of the existence of an active boron (B) uptake into the cortical cells induced by low B supply. The uptake of B was characterised in two tomato (Lycopersicon esculentum Mill.) genotypes: B-efficient FER and B-inefficient mutant T3238. In addition, pea (Pisum sativum L.) was used as an anatomically appropriate model for obtaining intact root cortex. Time course uptake studies in tomato indicate that the B-inefficient mutant was defective by the absence of an active low-B-induced uptake system in the cortex. Pea roots showed up to 10-fold higher accumulation of B into the cortex symplast at low (0.5 µm) external B supply in comparison to adequate B (10 µm) supply. Also, low-B-induced uptake of B was strongly inhibited by 2,4-dinitrophenol, indicating a metabolic energy-derived active component of B uptake at low external supply. Uptake of B by the cortical cells of tomato and pea plants appears to be a combination of both passive and active components, with a passive component prevailing at higher external B. An active component of B uptake suppressed by either adequate or high B supply might indicate a downregulation of plasma membrane-associated B transporter(s) in root cortical cells.

19.
New Phytol ; 177(4): 899-906, 2008.
Artigo em Inglês | MEDLINE | ID: mdl-18179601

RESUMO

Iron (Fe) deficiency is increasingly being observed in cropping systems with frequent glyphosate applications. A likely reason for this is that glyphosate interferes with root uptake of Fe by inhibiting ferric reductase in roots required for Fe acquisition by dicot and nongrass species. This study investigated the role of drift rates of glyphosate (0.32, 0.95 or 1.89 mm glyphosate corresponding to 1, 3 and 6% of the recommended herbicidal dose, respectively) on ferric reductase activity of sunflower (Helianthus annuus) roots grown under Fe deficiency conditions. Application of 1.89 mm glyphosate resulted in almost 50% inhibition of ferric reductase within 6 h and complete inhibition 24 h after the treatment. Even at lower rates of glyphosate (e.g. 0.32 mm and 0.95 mm), ferric reductase was inhibited. Soluble sugar concentration and the NAD(P)H oxidizing capacity of apical roots were not decreased by the glyphosate applications. To our knowledge, this is the first study reporting the effects of glyphosate on ferric reductase activity. The nature of the inhibitory effect of glyphosate on ferric reductase could not be identified. Impaired ferric reductase could be a major reason for the increasingly observed Fe deficiency in cropping systems associated with widespread glyphosate usage.


Assuntos
FMN Redutase/antagonistas & inibidores , Glicina/análogos & derivados , Helianthus/efeitos dos fármacos , Deficiências de Ferro , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/enzimologia , Glicina/farmacologia , Helianthus/metabolismo , Herbicidas/farmacologia , Folhas de Planta/efeitos dos fármacos , Folhas de Planta/metabolismo , Fatores de Tempo , Glifosato
20.
Funct Plant Biol ; 34(5): 402-408, 2007 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32689367

RESUMO

Cucumber (Cucumis sativus L.) plants were precultured for 7 days in either optimal (10 µm) or low (0.5 µm) Fe conditions and then grown for further 5 days in a N-free nutrient solution with (+Fe) or without (-Fe) 10 µm Fe. Thereafter NO3- (4 mm) was added to the nutrient solution for 24 h and, concomitantly, half of the -Fe plants were treated with 1 µm Fe complexed to water extractable humic substances (WEHS). Supply of NO3- to +Fe-N-deprived plants caused a large induction in the capacity to take up the anion by roots, which was accompanied by a rise in root-shoot NO3- concentration. The -Fe plants showed a lower level of induction of NO3- uptake and hence a lower accumulation of the anion in the tissues, these effects being reversed by supply of Fe-WEHS. Supply of either NO3-- or NH4+-N (+/- Fe-WEHS) to -Fe plants promoted the development of the root FeIII-chelate reductase activity, but the capacity of roots to take up the Fe2+ remained unaffected. Results show that an inadequate Fe supply can limit the acquisition of NO3-, whereas NO3- supply can affect Fe uptake by influencing the development and maintenance of a high FeIII-chelate reducing capacity.

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