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1.
Control of the development of iron-efficiency reactions in potato as a response to iron deficiency is located in the roots 总被引:7,自引:3,他引:4
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Roots of potato plants (Solanum tuberosum cv Bintje) growing on low Fe nutrient solution developed the characteristic Fe efficiency reactions, such as high ferric reductase activity, proton extrusion and increased root hair formation. Roots from a tuber with sprout removed, when grown on Fe-free nutrient solution, also expressed these reactions; transfer to iron-containing medium resulted in their complete disappearance within 10 days. Roots growing on 2% sucrose in sterile Murashige-Skoog medium increased their ferric reductase activity upon withholding Fe and formed transfer cells. It is concluded that potato roots themselves control the development of Fe-efficiency reactions, and that the shoot may exert a modulating influence on their expression. 相似文献
2.
Bienfait HF 《Plant physiology》1988,88(3):785-787
Fe-deficient dicotyledons develop Fe-efficiency reactions, such as proton extrusion and ferric chelate reduction activity, which are located in the plasma membranes of the root epidermal cells. The fer mutant of tomato (Lycopersicon esculentum Mill.) cannot develop these reactions. Membranes were isolated from roots of wild-type (FER) and mutant (fer) tomato plants grown on nutrient solution with high and low Fe concentrations. Two proteins were identified which are synthesized under the control of the FER gene. 相似文献
3.
Ferric citrate, the form in which iron is transported in dicotyledonous plants, diffuses slowly through cotton cellulose dialysis membranes, used to serve as a model for plant cell walls. KCl at m M concentrations stimulates diffusion.Photoreduction of ferric citrate results in a rapid and nearly complete reduction of iron when the citrate concentration is low (50 M) as in the xylem sap of plants growing on non-calcareous soils. In 1 m M citrate, as in the xylem sap of plants that activate their Fe-efficiency reactions, fast reoxidation prevents the buildup of high ferrous levels until after citrate has been largely broken down by photodestruction.Photodestruction of citrate, catalyzed by iron, results in increase of pH in the solution and in the formation of a non-dialyzable form of iron, and thus can lead to deposition of inactive iron in leaves. 相似文献
4.
The biosynthesis of 14C-IAA from 14C-tryptophan applied to abraded leaves of Ricinus communis and its subsequent export through the phloem were studied. Phloem sap was collected at intervals from incisions made in the stem below the IAA fed leaf. Any upward movement of label through the phloem or downward movement of phloem mobile compounds from leaves above the treated one were restricted by bark-ringing the plants.TLC and HPLC analyses of the collected sap indicate that some conversion of 14C-tryptophan to 14C-IAA had occurred. Subsequent GC-MS analysis of the HPLC purified samples of phloem sap revealed high levels of endogenous IAA transported from the fed leaf. The high ratio of unlabelled/labelled IAA in the phloem sap makes unequivocal confirmation by GC-MS of the predicted biosynthesis of 14C-IAA impossible. It is postulated that IAA is synthesised from tryptophan in mature leaves and exported to developing sink tissues with the flow of photoassimilates in the phloem. 相似文献
5.
Levels of free tryptophan in the leaves, phloem and xylem saps of Ricinus communis L. were determined by colorimetric assay. Values of 0.38 g ml-1 in root pressure sap and 96.0 g ml-1 in phloem sap were recorded. Tryptophan levels were highest in mature and senescing leaves. Levels of indoleacetic acid (IAA) in the phloem sap and leaves were determined by gas chromatography—mass spectrometry using a deuterated internal standard. A mean value of 13.0 ng ml-1 was recorded in phloem sap. The distribution in the leaves showed an inverse relationship to that of tryptophan, being highest in young leaves.Abbreviations IAA
indoleacetic acid
- GC-MS
Gas chromatography-mass spectrometry
- PFP-derivative
pentafluoropropionyl-derivative
- TLC
thin layer chromatography 相似文献
6.
Zeevaart JA 《Plant physiology》1977,59(5):788-791
The sites of abscisic acid (ABA) synthesis and metabolism in Ricinus communis L. were investigated by analyzing the levels of ABA and its two metabolites phaseic acid (PA) and dihydrophaseic acid (DPA) in the shoot tips, mature leaves, and phloem sap of stressed and nonstressed plants. 相似文献
7.
Are phloem amino acids involved in the shoot to root control of NO3- uptake in Ricinus communis plants? 总被引:3,自引:0,他引:3
The putative role of phloem amino acids as negative feedback signals for
root NO3- uptake was investigated in
Ricinus communis L. The
NO3--grown plants were subjected to N-deficiency due
either to complete N-deprivation, or to localized N-deprivation on one side
of a split-root system. In comparison with controls, complete N-deprivation
resulted in a transient increase in
15NO3- influx, and in
profound changes in downward phloem transport of amino acids. Total amino
acid concentration in the phloem sap decreased by 40%, but responses
markedly differed between the individual amino acids. Concentrations of Gln
and Ser were rapidly lowered by 50%, while those of Val, Phe, Leu, and Ile
displayed a marked increase. Localized N-deprivation on one side of the
split root system also resulted in the up-regulation of
15NO3- influx in the roots
still supplied with NO3-. However, the amino acid
composition of the phloem sap directed to these roots was not modified by
the treatment, and remained similar to that in N-sufficient control plants.
Only amino acid transport to the N-deprived roots was affected as observed
in response to complete N-deprivation. The results from split-root plants
indicate that the response of root NO3- influx to
N-deficiency is controlled by shoot-borne regulatory signals, and provide a
case study where these signals are not related to a qualitative change or a
significant decrease in downward phloem transport of amino
acids. 相似文献
8.
黄瓜叶片对草酸铁的还原作用 总被引:2,自引:0,他引:2
铁还原作用在植物叶片对铁素吸收及利用过程中起关键作用.本研究表明相对于其它几种常用的铁螯合物如二乙基四乙酸铁(FeⅢEDTA)或柠檬酸铁,草酸铁更有利于黄瓜活体叶片及铁还原酶的作用,即表现出更高的铁还原活力.缺铁降低了黄瓜叶片中的铁还原活性.缺铁时叶片中的草酸含量不受影响,而富含在石灰性缺铁土壤中的碳酸氢根离子能使叶片中草酸含量显著提高. 相似文献
9.
Fabiana Antognoni Silvia Fornalè Claudia Grimmer Ewald Komor Nello Bagni 《Planta》1998,204(4):520-527
Polyamine content and enzyme activities in the biosynthetic and degradative pathways of polyamine metabolism were investigated
in sieve-tube sap, xylem sap and tissues of seedlings and adult plants of Ricinus communis L. Polyamines were present in tissues and translocation fluids of both seedlings and adult plants in relatively high amounts.
Only free polyamines were translocated through the plant, as indicated by the finding that only the free form was detected
in the phloem and the xylem sap. Removal of the endosperm increased the polyamine content in the sieve-tube exudate of seedlings.
The level and pattern of polyamines in tissue of adult leaves changed during leaf age, but not, however, in the sieve-tube
sap. Xylem sap was relatively poor in polyamines. Polyamine loading in the phloem was demonstrated by incubating cotyledons
with [14O]putrescine and several unlabelled polyamines. Feeding cotyledons with cadaverine and spermidine led to a decrease in the
level of putrescine in sieve-tube sap, indicating a competitive effect. Comparison of polyamine content in the tissue and
export rate showed that the export would deplete the leaves of polyamines within 1–3 d, if they were not replenished by biosynthesis.
Polyamine biosynthesis in Ricinus proceeds mostly via arginine decarboxylase, which in vitro is 100-fold more active than ornithine decarboxylase. The highest
arginine decarboxylase, ornithine decarboxylase and diamine oxidase activities were detected in cotyledons, while in sieve-tube
sap only a slight arginine decarboxylase activity was found.
Received: 18 March 1997 / Accepted: 20 August 1997 相似文献
10.
Spontaneous Phloem bleeding from cryopunctured fruits of a ureide-producing legume 总被引:4,自引:4,他引:0
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The vasculature of the dorsal suture of cowpea (Vigna unguiculata [L.] Walp) fruits bled a sugar-rich exudate when punctured with a fine needle previously cooled in liquid N2. Bleeding continued for many days at rates equivalent to 10% of the estimated current sugar intake of the fruit. A phloem origin for the exudate was suggested from its high levels (0.4-0.8 millimoles per milliliter) of sugar (98% of this as sucrose) and its high K+ content and high ratio of Mg2+ to Ca2+. Fruit cryopuncture sap became labeled with 14C following feeding of [14C]urea to leaves or adjacent walls of the fruit, of 14CO2 to the pod gas space, and of [14C] asparagine or [14C]allantoin to leaflets or cut shoots through the xylem. Rates of translocation of 14C-assimilates from a fed leaf to the puncture site on a subtended fruit were 21 to 38 centimeters per hour. Analysis of 14C distribution in phloem sap suggested that [14C]allantoin was metabolized to a greater extent in its passage to the fruit than was [14C] asparagine. Amino acid:ureide:nitrate ratios (nitrogen weight basis) of NO3-fed, non-nodulated plants were 20:2:78 in root bleeding xylem sap versus 90:10:0.1 for fruit phloem sap, suggesting that the shoot utilized NO3-nitrogen to synthesize amino acids prior to phloem transfer of nitrogen to the fruit. Feeding of 15NO3 to roots substantiated this conclusion. The amino acid:ureide ratio (nitrogen weight basis) of root xylem sap of symbiotic plants was 23:77 versus 89:11 for corresponding fruit phloem sap indicating intense metabolic transfer of ureide-nitrogen to amino acids by vegetative parts of the plant. 相似文献
11.
OsFRDL1 Is a Citrate Transporter Required for Efficient Translocation of Iron in Rice 总被引:6,自引:0,他引:6
Kengo Yokosho Naoki Yamaji Daisei Ueno Namiki Mitani Jian Feng Ma 《Plant physiology》2009,149(1):297-305
Multidrug and toxic compound extrusion (MATE) transporters represent a large family in plants, but their functions are poorly understood. Here, we report the function of a rice (Oryza sativa) MATE gene (Os03g0216700, OsFRDL1), the closest homolog of barley (Hordeum vulgare) HvAACT1 (aluminum [Al]-activated citrate transporter 1), in terms of metal stress (iron [Fe] deficiency and Al toxicity). This gene was mainly expressed in the roots and the expression level was not affected by either Fe deficiency or Al toxicity. Knockout of this gene resulted in leaf chlorosis, lower leaf Fe concentration, higher accumulation of zinc and manganese concentration in the leaves, and precipitation of Fe in the root's stele. The concentration of citrate and ferric iron in the xylem sap was lower in the knockout line compared to the wild-type rice. Heterologous expression of OsFRDL1 in Xenopus oocytes showed transport activity for citrate. Immunostaining showed that OsFRDL1 was localized at the pericycle cells of the roots. On the other hand, there was no difference in the Al-induced secretion of citrate from the roots between the knockout line and the wild-type rice. Taken together, our results indicate that OsFRDL1 is a citrate transporter localized at the pericycle cells, which is necessary for efficient translocation of Fe to the shoot as a Fe-citrate complex. 相似文献
12.
13.
Changes in the amino acid composition and protein modification in phloem sap of rice 总被引:1,自引:0,他引:1
Pure phloem sap was collected from insects feeding on rice (Oryza sativa L.) leaves by a laser technique similar to the aphid stylet technique. Rapid circulation of nitrogen in the sieve tubes was demonstrated directly using 15N as a tracer. Application to the roots of the metabolic inhibitors of amino acids, aminooxyacetate and methioninesulfoximine, changed the amino acid composition in the sieve tubes. Feeding methionine to leaf tips resulted in its bulk transfer into the sieve tubes.
In vitro experiments confirmed the existence of protein kinases in the pure rice phloem sap. The phosphorylation status of the sieve tube sap proteins was affected by the light regime. The possibility that changes in chemical composition or protein modification such as phosphorylation in the sieve tubes might affect plant growth are discussed.Analysis of pure phloem sap collected from rice plants by insect laser technique has shown dynamic changes in the chemical composition and the quality of proteins in the sap. 相似文献
14.
Cytokinin-like activity in samples of xylem and phloem sap collected from field-grown plants of white lupin (Lupinus albus L.) over a period of 9 to 24 weeks after sowing was measured using the soybean hypocotyl callus bioassay following paper chromatographic separation. The phloem sap was collected from shallow incisions made at the base of the stem, the base of the inflorescence (e.g. stem top), the petioles, and the base and tip of the fruit. Xylem sap was collected as root exudate from the stump of plants severed a few centimeters above ground level. Concentration of cytokinin-like substances was highest in phloem sap collected from the base of the inflorescence and showed an increase over the entire sampling period (from week 10 [61 nanogram zeatin equivalents] to week 24 [407 nanogram zeatin equivalents]). Concentrations in the xylem sap and in the other phloem saps were generally lower. Relatively high concentrations of cytokinin-like substances in petiole phloem sap (70 to 130 nanogram zeatin equivalents per milliliter) coincided in time with high concentrations in sap from the base of the inflorescence (see above). Concentrations in sap (phloem or xylem) from the base of the stem were very much lower. This finding is consistent with movement of cytokinins from leaves into the developing inflorescence and fruit, rather than direct input to the fruit from xylem sap. However, an earlier movement of cytokinins from roots into leaves via the xylem cannot be ruled out. Sap collected at an 18-week harvest was additionally separated by sequential C18 reversed-phase high performance liquid chromatography → NH2 normal phase high performance liquid chromatography, bioassayed, and then analyzed by electron impact gas chromatography-mass spectrometry. Identification of zeatin riboside and dihydrozeatin as two of the major cytokinins in combined sap samples was accomplished by gas chromatography-mass spectrometry-selected ion monitoring. 相似文献
15.
Sieve tube sap exuded from the cut hypocotyl of castor bean seedlings (Ricinus communis L.) was found to contain 0.2–0.5 mmol m?3abscisic acid (ABA). The ABA concentration in the sieve tube sap always exceeded that in root pressure exudate under a wide range of water supply. Exudation of sieve tube sap from the cut hypocotyls caused water loss, and this induced ‘water shortage’ in the cotyledons which resulted in the ABA concentration in the cotyledons increasing by 3-fold and that in the sieve tube sap increasing by up to 50-fold within 7h. The wounded surface of the cut hypocotyl was not responsible for the ABA increase. Incubation of the cotyledons of endosperm-free seedlings in various ABA concentrations (up to 100 mmol m?3) increased the ABA concentration in sieve tube sap. The concomitant increase in ABA, both in cotyledons and in sieve tube sap, had no effect on the phloem loading of sucrose, K+ and Mg2+ within the experimental period, i.e. up to 10h. It can be concluded that (i) the phloem is an important transport path for ABA, (ii) water stress at the phloem loading sites elevates phloem-mobile ABA, which may then serve as a water stress signal for sinks, for example stem and roots (not only for stomata), and (iii) the ABA concentration of cells next to or in the phloem is more important than the average ABA content in the whole cotyledon for determining the ABA concentration in sieve tube sap. 相似文献
16.
Louis Grillet Laurent Ouerdane Paulina Flis Minh Thi Thanh Hoang Marie-Pierre Isaure Ryszard Lobinski Catherine Curie Stéphane Mari 《The Journal of biological chemistry》2014,289(5):2515-2525
Iron (Fe) is essential for virtually all living organisms. The identification of the chemical forms of iron (the speciation) circulating in and between cells is crucial to further understand the mechanisms of iron delivery to its final targets. Here we analyzed how iron is transported to the seeds by the chemical identification of iron complexes that are delivered to embryos, followed by the biochemical characterization of the transport of these complexes by the embryo, using the pea (Pisum sativum) as a model species. We have found that iron circulates as ferric complexes with citrate and malate (Fe(III)3Cit2Mal2, Fe(III)3Cit3Mal1, Fe(III)Cit2). Because dicotyledonous plants only transport ferrous iron, we checked whether embryos were capable of reducing iron of these complexes. Indeed, embryos did express a constitutively high ferric reduction activity. Surprisingly, iron(III) reduction is not catalyzed by the expected membrane-bound ferric reductase. Instead, embryos efflux high amounts of ascorbate that chemically reduce iron(III) from citrate-malate complexes. In vitro transport experiments on isolated embryos using radiolabeled 55Fe demonstrated that this ascorbate-mediated reduction is an obligatory step for the uptake of iron(II). Moreover, the ascorbate efflux activity was also measured in Arabidopsis embryos, suggesting that this new iron transport system may be generic to dicotyledonous plants. Finally, in embryos of the ascorbate-deficient mutants vtc2-4, vtc5-1, and vtc5-2, the reducing activity and the iron concentration were reduced significantly. Taken together, our results identified a new iron transport mechanism in plants that could play a major role to control iron loading in seeds. 相似文献
17.
Apple rootstocks were grown with either 0.02 ppm Fe (Fe0) or5 ppm (Fe3), to give very chlorotic or dark-green plants. Toinvestigate whether iron can be supplied through leaves insteadof roots the shoots of half the plants in each treatment weredipped periodically in solutions of iron. This prevented chlorosisin Fe0 plants and increased their growth, which did not, however,equal that of Fe3 plants supplied with iron through the roots.Growth of Fe3 plants was reduced by dipping. Iron was not translocated from leaves to roots, although theconcentration in leaves was greatly increased by dipping. Dippingreduced the amount of manganese in Fe0 roots to one-quarterof that in roots of undipped Fe0 plants. Effects of treatmentson nitrogen, potassium, calcium, magnesium, and copper levelsare also described. 相似文献
18.
Iron nutrition affects cadmium accumulation and toxicity in rice plants 总被引:12,自引:0,他引:12
Guosheng Shao Mingxue Chen Weixia Wang Renxiang Mou Guoping Zhang 《Plant Growth Regulation》2007,53(1):33-42
The effect of iron (Fe) nutrition on cadmium (Cd) toxicity and accumulation in rice plants was studied using a hydroponic
system. The inhibitory effect of Cd on plant growth and chlorophyll content (SPAD value) was dependent on Fe level and the
genotype. Malondialdehyde (MDA) content in leaves and roots was not much affected by an increased Cd stress at 0.171 mg l−1 Fe, but it showed a rapid increase when the plants were exposed to moderate (1.89 mg l−1) and high (16.8 mg l−1) Fe levels. High Fe nutrition caused a marked reduction in Cd content in both leaves and roots. Fe content in plants was
lower at high Cd (5.0 μM) stress than at low Cd (<1.0 μM) stress. Cd stress increased both superoxide dismutase (SOD) and
peroxidase (POD) activities at low and moderate Fe levels. However, with high Fe level, it increased the POD activity, but
reduced the SOD activity. Our results substantiate the hypothesis that cell membrane-bound iron transporter (carrier) involved
in high-affinity iron transport systems can also transport Cd, and both these ions may compete for this common carrier. The
study further showed that there were significant correlations between MDA and Fe contents in leaves and roots of rice plants.
It is suggested that the occurrence of oxidative stress in plants exposed to Cd stress is mediated by Fe nutrition. The present
results also show that Cd stress affects the uptake of Cu and Zn. 相似文献
19.
During growth of Ricinus communis seedlings, magnesium ions are mobilized in the endosperm, taken up by and accumulated to very high levels (150 μmol·g FW?1) in the cotyledons, and translocated to hypocotyl and roots. The magnesium gain from days 6 to 7 in the cotyledons and the seedling axis necessitates a total up-take rate of 600 nmol·h?1-seedling?1 and the phloem translocation rate must amount to 200 nmol·h?1. seedling?1. The phloem loading of magnesium and the regulatory properties of this process were investigated, making specific use of the ability to collect pure phloem sap from the cut hypocotyl of 6-d-old Ricinus seedlings. The concentration of magnesium in sieve-tube sap (5 mM) was fairly constant under many incubation conditions, e.g. incubation in magnesium-free buffer, incubation with different cations (K+, Na+, NH 4 + ) or anions (Cl?, NO 4 - , SO 4 2- ), or incubation with sucrose and amino acids. Even addition of magnesium chloride to the cotyledons did not enhance phloem loading of magnesium ions. Therefore the high magnesium content of the cotyledons was sufficient for continuous phloem loading of magnesium, irrespective of external ionic conditions. Also, the flow rate of sieve-tube sap did not influence the magnesium concentration in the sap. Only the incubation with sulfate and phosphate ions increased the magnesium-ion concentration in the phloem. Magnesium sulfate offered to the cotyledons caused a threefold increase of magnesium ions in the sieve-tube sap, which was inhibited by Na+, NH 4 + and Ca2+ in rising order, but not by K+. Incubation with phosphate for a prolonged period (8 h) led to an increased mobilization of intra-cotyle-donary magnesium and an enhanced phloem loading of mobilized magnesium. It is concluded that phosphate availability is a decisive factor for mobilization and translocation of magnesium ions within the plant. 相似文献
20.