Differential transport of Zn, Me and sucrose along the longitudinal axis of developing wheat grains

The hypothesis that Zn and Mn are transported within the grain in a similar manner to sucrose was investigated in the developing wheat grain. Detached ears were cultured in solution containing ⁶⁵Zn, ⁵⁴Mn and [¹⁴C]-sucrose for 10 to 120 min at 18–22 days post-anthesis. At different times the grain was cut transversely into 1-mm sections and the radioactivity in each section determined The embryo region was damaged in some grains to investigate the effect of reduced accumulation rate on the transport of ⁶⁵Za, ⁵⁴Mn and [¹⁴C]-sucrose to the embryo. The distribution of ⁶⁵Zn. ⁵⁴Mn and [¹⁴C]-sucrose between the endosperm cavity sap. endosperm, embryo and pericarp in grains labelled for 2.5 and 6 h at 18–22 days post-anthesis was also determined. [¹⁴C]-su-crose was initially high in the first, embryo-containing section of the grain but decreased progressively to the distal end of the grain. The amount of ⁶⁵Zn along the longitudinal axis of the grain was distributed evenly in each 1-mm section, whilst ⁵⁴Mn accumulated exponentially in the first proximal 1-mm section of the grain and was distributed evenly in the remaining sections. Damaging the embryo had no effect on ⁶⁵Zn and ⁵⁴Mn transport to the section containing the embryo. The pericarp contained almost all of the grain ⁶⁵Za and ⁵⁴Mn, with small amounts found in the embryo, endosperm and endosperm cavity sap. Increasing amounts of [¹⁴C]-sucrose were found in the endosperm as time progressed. The rate of accumulation of ⁶⁵Zn, ⁵⁴Mn and [¹⁴C]-sucrose was much higher in the embiyo than the endosperm: the difference between the embryo and endosperm was especially large for ⁶⁵Zn and ⁵⁴Mn. It is suggested that ⁶⁵Zn and ⁵⁴Mn are not transported within the grain in the same way as [¹⁴C]-sucrose. [¹⁴C]-sucrose moves laterally out of the vascular system of the crease into the endosperm cavity and is subsequently taken up and stored in the endosperm. In contrast, ⁶⁵Zn and ⁵⁴Mn appear to be retained within the vascular system of the crease and may be transported more slowly to grain parts such as the embryo and pericarp tissue.     

Transport of zinc and manganese to developing wheat grains

An understanding of the transport pathway used by Zn and Mn to enter developing grains may allow measures to increase the Zn and Mn content of wheat grain grown on Zn/Mn deficient soils. For this reason, transport of Zn and Mn into developing grains of wheat ( Triticum aestivum L. cv. Aroona) was investigated. Detached ears (18–22 days post-anthesis) were cultured for 48 h in a solution containing 185 kBq of ⁶⁵Zn and 185 kBq of ⁵⁴Mn. Transport of ⁶⁵Zn to the grain was unaffected by removal of glumes but was slightly reduced after the lemma was removed. Heat girdling the peduncle slightly reduced the amount of ⁶⁵Zn transported to the grain, whilst heat girdling the rachilla reduced transport of ⁶⁵Zn to the grain to a greater degree, suggesting phloem transport to the rachilla. The transport inhibitor CCCP (carbonyl cyanide m -chlorophenyl hydrazone) blocked ⁶⁵Zn transport to grain but not to lemma and glumes. Removing glumes and lemma and heat girdling the peduncle did not affect transport of ⁵⁴Mn, but transport was slightly affected by heat girdling the rachilla, indicating xylem transport. CCCP blocked transport of ⁵⁴Mn into the grain but not to lemma and glumes. It was concluded that xylem-to-phloem transfer of Zn occurs in the rachis and to a lesser extent in peduncle and lemma. The results suggest that the lemma may be an important site for phloem loading when the concentration of Zn within the xylem is high. The data also suggest that Mn was predominantly translocated to the spikelets in the xylem, but that transport to the grain was dependent upon membrane transport before entering the grain. Phloem loading of Mn into the grain vascular system may have occurred at the site of xylem discontinuity in the floral axis.     

The reduction in zinc concentration of wheat grain upon increased phosphorus-fertilization and its mitigation by foliar zinc application

Background and aims

Malnutrition resulting from zinc (Zn) and iron (Fe) deficiency has become a global issue. Excessive phosphorus (P) application may aggravate this issue due to the interactions of P and micronutrients in soil crop. Crop grain micronutrients associated with P applications and the increase of grain Zn by Zn fertilization were field-evaluated.

Methods

A field experiment with wheat was conducted to quantify the effect of P applications on grain micronutrient quality during two cropping seasons. The effect of foliar Zn applications on grain Zn quality with varied P applications was tested in 2011.

Results

Phosphorus applications decreased grain Zn concentration by 17–56%, while grain levels of Fe, manganese (Mn) and copper (Cu) either remained the same or increased. Although P applications increased grain yield, they restricted the accumulation of shoot Zn, but enhanced the accumulation of shoot Fe, Cu and especially Mn. In 2011, foliar Zn application restored the grain Zn to levels occurring without P and Zn application, and consequently reduced the grain P/Zn molar ratio by 19–53% than that without Zn application.

Conclusions

Foliar Zn application may be needed to achieve both favorable yield and grain Zn quality of wheat in production areas where soil P is building up.     

The expression of heterologous Fe (III) phytosiderophore transporter HvYS1 in rice increases Fe uptake,translocation and seed loading and excludes heavy metals by selective Fe transport

Many metal transporters in plants are promiscuous, accommodating multiple divalent cations including some which are toxic to humans. Previous attempts to increase the iron (Fe) and zinc (Zn) content of rice endosperm by overexpressing different metal transporters have therefore led unintentionally to the accumulation of copper (Cu), manganese (Mn) and cadmium (Cd). Unlike other metal transporters, barley Yellow Stripe 1 (HvYS1) is specific for Fe. We investigated the mechanistic basis of this preference by constitutively expressing HvYS1 in rice under the control of the maize ubiquitin1 promoter and comparing the mobilization and loading of different metals. Plants expressing HvYS1 showed modest increases in Fe uptake, root‐to‐shoot translocation, seed accumulation and endosperm loading, but without any change in the uptake and root‐to‐shoot translocation of Zn, Mn or Cu, confirming the selective transport of Fe. The concentrations of Zn and Mn in the endosperm did not differ significantly between the wild‐type and HvYS1 lines, but the transgenic endosperm contained significantly lower concentrations of Cu. Furthermore, the transgenic lines showed a significantly reduced Cd uptake, root‐to‐shoot translocation and accumulation in the seeds. The underlying mechanism of metal uptake and translocation reflects the down‐regulation of promiscuous endogenous metal transporters revealing an internal feedback mechanism that limits seed loading with Fe. This promotes the preferential mobilization and loading of Fe, therefore displacing Cu and Cd in the seed.     

Copper Uptake and Its Effect on Metal Distribution in Root Growth Zones of Commelina communis Revealed by SRXRF

To explore the copper uptake mechanisms by the Cu-tolerant plant Commelina communis, the contents of Cu and other metals (including Fe, Zn, and Mn) in roots were detected using atomic absorption spectrometer under transporter inhibitors, partial element deficiency, or Cu excess treatments, while distribution characters of Cu and other metals in root growth zones were investigated by synchrotron radiation X-ray fluorescence spectroscopy (SRXRF). Cu uptake was inhibited by the uncoupler DNP and P-type ATPase inhibitor Na₃VO₄, not by the Ca²⁺ ion channel inhibitor LaCl₃, suggesting that Cu could probably be assimilated actively by root and be related with P-type ATPase, but not through Ca²⁺ ion channel. Fe or Zn deficiency could enhance Cu uptake, while 100 μM Cu inhibited Fe, Zn, and Mn accumulation in roots significantly. Metal distribution under 100 μM Cu treatment was investigated by SRXRF. High level of Cu was found in the root meristem, and higher Cu concentrations were observed in the vascular cylinder than those in the endodermis, further demonstrating the initiative Cu transport in the root of C. communis. Under excess Cu stress, most Fe was located in the epidermis, and Fe concentrations in the endodermis were higher than those in the vascular cylinder, suggesting Cu and Fe competition not only in the epidermal cells but also for the intercellular and intracellular transport in roots. Zn was present in the meristem and the vascular cylinder similar to Cu. Cu and Zn showed a similar pattern. Mn behaves as Zn does, but not like Fe.     

Import of sucrose and its transformation to starch in the developing sorghum caryopsis

Levels of soluble and bound invertases and amylases were studied in relation to the changes in the free sugars and the accumulation of starch in the developing sorghum [Sorghum bicolor (L.) Moench, cv. spv. 351] caryopsis and its associated bractspedicel. Besides sucrose, glucose and fructose as the principal sugars, small amounts of sugars of the raffinose series were detected in the developing caryopsis. Through out the period of caryopsis development, the amount of reducing sugars was higher than that of sucrose. With the advancement in the development of the caryopsis, the contents and levels of sucrose rose with a concomitant fall in the activity of soluble acid (pH 4.8) invertase (EC 3.2.1.26) in the endosperm. In the pericarp-aleurone layer, the activity of soluble acid invertase predominated over soluble neutral (pH 7.5) invertase (EC 3.2.1.27). The activity of bound acid invertase declined with the ageing of the caryopsis. In bracts-pedicel, the activity of bound invertase and the levels of reducing sugars peaked around 18 days post anthesis. In these organs, the level of starch gradually decreased concomitantly with an increase in its level in the developing caryopsis. Amylases (EC 3.2.1.1 and 3.2.1.2) are distributed in the endosperm as well as in the pericarp-aleurone layer. On culturing detached ears in [U-¹⁴C]-sucrose solution for 6 h in the dark at 25°C, 80–90% of the ¹⁴C of extracted major sugars (i.e. sucrose + glucose + fructose) of the caryopsis appeared in sucrose alone. In comparison with the effects of glucose or fructose, transport into the caryopsis of ¹⁴C from [U-¹⁴C]-sucrose supplied to detached ears was promoted by the addition to the radiolabelled sucrose solution of 1% unlabelled sucrose. Addition to the [U-¹⁴C]-sucrose solution fed to the detached ears of 20 mM NaN₃ or HgCl₂ or galactose, lowered the amount of ¹⁴C in the free sugars and starch of the earyopsis.     

Maize grain concentrations and above-ground shoot acquisition of micronutrients as affected by intercropping with turnip, faba bean, chickpea, and soybean

Most research on micronutrients in maize has focused on maize grown as a monocrop. The aim of this study was to determine the effects of intercropping on the concentrations of micronutrients in maize grain and their acquisition via the shoot. We conducted field experiments to investigate the effects of intercropping with turnip (Brassica campestris L.), faba bean (Vicia faba L.), chickpea (Cicer arietinum L.), and soybean (Glycine max L.) on the iron (Fe), manganese (Mn), copper (Cu) and zinc (Zn) concentrations in the grain and their acquisition via the above-ground shoots of maize (Zea mays L.). Compared with monocropped maize grain, the grain of maize intercropped with legumes showed lower concentrations of Fe, Mn, Cu, and Zn and lower values of their corresponding harvest indexes. The micronutrient concentrations and harvest indexes in grain of maize intercropped with turnip were the same as those in monocropped maize grain. Intercropping stimulated the above-ground maize shoot acquisition of Fe, Mn, Cu and Zn, when averaged over different phosphorus (P) application rates. To our knowledge, this is the first report on the effects of intercropping on micronutrient concentrations in maize grain and on micronutrients acquisition via maize shoots (straw+grain). The maize grain Fe and Cu concentrations, but not Mn and Zn concentrations, were negatively correlated with maize grain yields. The concentrations of Fe, Mn, Cu, and Zn in maize grain were positively correlated with their corresponding harvest indexes. The decreased Fe, Mn, Cu, and Zn concentrations in grain of maize intercropped with legumes were attributed to reduced translocation of Fe, Mn, Cu, and Zn from vegetative tissues to grains. This may also be related to the delayed senescence of maize plants intercropped with legumes. We conclude that turnip/maize intercropping is beneficial to obtain high maize grain yield without decreased concentrations of Fe, Mn, Cu, and Zn in the grain. Further research is required to clarify the mechanisms underlying the changes in micronutrient concentrations in grain of intercropped maize.     

Effect of Trichoderma asperellum strain T34 on iron, copper, manganese, and zinc uptake by wheat grown on a calcareous medium

Rhizosphere microbes may enhance nutrient uptake by plants. Here we studied the effect of Trichoderma asperellum inoculation on the uptake of Fe, Cu, Mn, and Zn by wheat (Triticum aestivum L) grown in a calcareous medium. To this end, an experiment involving two factors, namely Fe enrichment (ferrihydrite enrichment and non-enrichment of the growing medium), and inoculation/non-inoculation with Trichoderma asperellum strain T34, was performed twice under the same conditions. The increase in Fe availability as a result of ferrihydrite enrichment did not enhance plant dry matter production. The effect of T34 on the concentration of Fe, Cu, Mn and Zn, and the total amount of Cu, Mn, and Zn in the aerial parts differed depending on the degree of ferrihydrite enrichment. Inoculation with T34 increased Fe concentration in Fe-deficient media, thus revealing a positive effect of this microorganism on Fe nutrition in wheat. However, T34 significantly decreased the concentration and total amount of Cu, Mn, and Zn in the aerial parts, but only in ferrihydrite-enriched medium. This adverse effect of T34 on Cu, Mn, and Zn uptake by wheat plants may have been related to conditions of restricted availability where potential competition for nutrients between microorganisms and plants can be more marked.     

Long distance transport of potassium in cereals during grain filling in detached ears

Ears of wheat plants ( Triticum aestivum L. cv. Kolibri), which were given different and uniform K⁺-nutrition in two experiments, were cut at 2, 4 and 6 weeks after anthesis at 15 cm below the ear. These detached ears were fed 30 m M (experiment 1) or 15, 30, 60 or 90 m M ⁸⁶Rb-K₂ malate (experiment 2) and 146 m M [¹⁴C]-sucrose. After a pulse period of 6 and 4 h, respectively, the ears were transferred to identical non-labeled solutions for additional 0, 4, 8 or 20 h.
About 50% of the K⁺ and sucrose supplied was absorbed by detached ears. This rate declined with plant age and decreasing transpiration. Within the 6 and 4 h uptake period less than 7% of the absorbed K⁺, but 20% of the sucrose taken up were incorporated into the grain. During the chase period labeled K⁺ in the grain increased to 15% and ¹⁴C even to 50% of total tracer uptake. Incorporation of labeled K⁺ into the grain was not affected by the previous K⁺ nutrition of the plant and was proportional to the K⁺ concentration in the uptake solution. Transition of K⁺ from xylem into phloem during its acropetal transport is assumed. No evidence was found that the grain itself could control its uptake of K⁺.     

Physiological responses of wheat genotypes grown in chelator-buffered nutrient solutions with increasing concentrations of excess HEDTA

The chelator-buffered nutrient solutions containing excess chelator have been used frequently in the micronutrient research, but potential toxicity of the excess chelator has not been ascertained. The present study was conducted to test effects of four concentrations of excess HEDTA [ N-(2-hydroxyethyl)ethylenedinitrilotriacetic acid] and two levels of total Zn on growth, root exudation, and nutrient uptake and transport by Triticum aestivum L. (cv. Aroona) and Triticum turgidum L. conv. durum (Desf.) MacKey (cv. Durati) genotypes differing in tolerance to Zn deficiency. Excess HEDTA at 50 μM reduced root and shoot growth and caused visual toxicity symptoms (necrotic lesions) on leaves; these effects were generally absent at lower concentrations of excess HEDTA. Root exudation of phytosiderophores increased with increasing concentrations of excess HEDTA at deficient and sufficient Zn levels, and was higher in Zn-deficiency-tolerant Aroona than in Zn-deficiency-sensitive Durati wheat. Shoot and root Zn concentrations showed a saturable response to increasing Zn²⁺ activities in solution. Excess HEDTA at 50 μM caused an increase in shoot concentrations of Fe and a decrease in concentrations of Mn and Cu. An average rate of Zn uptake increased with an increase in Zn²⁺ ionic activity in solution, with Zn-deficiency-tolerant Aroona having a higher rate of Zn uptake than Zn-deficiency-sensitive Durati in the deficiency range of Zn²⁺ activities. Average uptake rates of Mn and Cu decreased with an increase in concentration of excess HEDTA. Similar observations were noted for transport of Mn and Cu to shoots, while Zn transport to shoots was proportional to Zn²⁺ activities in solution. It was concluded that excess HEDTA at 50 μM adversely affects wheat growth and physiology, while excess of 25 μM or less does not cause measurable toxicity. This revised version was published online in June 2006 with corrections to the Cover Date.     

Fluoride-induced alteration of carbon and nitrogen metabolism in developing wheat grains

Effect of fluoride (10 and 50 mM) on the activities of sucrose metabolizing enzymes, alkaline inorganic pyrophosphatase, and transaminases in relation to the accumulation of free sugars, starch, and soluble protein was studied in detached ears of wheat cultured in a liquid medium. Culturing for 5 d in the presence of fluoride reduced the amount of grain starch whereas contents of total free sugars, particularly sucrose, and soluble protein increased. Fluoride inhibited the activities of soluble acid and neutral invertases, as well as sucrose synthase acting in the cleavage direction. Uptake of uniformly labelled ¹⁴C-sucrose or fructose was also drastically reduced by fluoride. Glutamate-oxaloacetate transaminase (GOT) and glutamate-pyruvate transaminase (GPT) activities also increased with fluoride addition in correspondence with an increase in soluble protein. Apparently, the wheat grain responds to fluoride-mediated disruption of carbon metabolism by a compensatory effect on nitrogen metabolism. This revised version was published online in July 2006 with corrections to the Cover Date.     

Translocation of copper and other micronutrients in tomato plants (Lycopersicon esculentum Mill.): nicotianamine-stimulated copper transport in the xylem

The influence of the endogenous micronutrient chelator, nicotianamine(NA), and of Cu nutrition on the distribution of Cu, Fe, Mn,Zn, and NA was investigated in eight different shoot organs,roots, and in xylem exudates of the NA-containing tomato wildtype Lycopersicon esculentum Mill. cv. Bonner Beste and itsNA-less mutant chloronerva. Contrary to the other heavy metals, copper transport in thexylem was inefficient in the mutant and was enhanced by an applicationof NA to the roots or leaves in proportion to the applied NAconcentration. Also, with NA application, the Cu concentrationin mutant roots decreased significantly, and increased in theshoot. Fe and Mn transport in the xylem was greater in the mutantthan in the wild type, and was decreased in the mutant by theapplication of NA to the leaves. Zn transport in the xylem wasthe same in both genotypes and was unaffected by NA application.After application of NA to leaves and roots of the mutant itwas possible to detect NA in the xylem exudate (up to 2nmolNA(g^–1 root FWh^–1). High Cu supply (3 µM) resulted in higher Cu and Mn concentrationsin all organs of the wild type as compared to mutant organs,but Fe concentrations were not influenced. Under high Cu supply(3µM) the NA concentrations of roots and the three youngestleaves of the wild type were higher than under normal Cu supply(0.3 µM). The highest concentrations were found in theshoot apex under both Cu conditions (up to 361 nmol NAg^–1FW). It is concluded from our experiments and from the high stabilityconstant of the NA-Cu-complex (log K= 18.6) that NA is involvedin Cu translocation whereas for the translocation of Fe, Mn,and Zn, NA is not essential. Key words: Copper transport, micronutrients, mobilization, nicotianamine, xylem     

Specificity of transport of bleomycin and cobalt-bleomycin in L5178Y cells

The mechanism of transport of [³H]peplomycin (PEP), a new member of bleomycin group antibiotics, was studied in cultured L5178Y mouse leukemic cells. Cobalt ions enhanced the uptake of PEP, but Cu, Zn, Fe(II) and Fe(III) had no effect. The initial rate of uptake of cobalt chelated PEP [PEP(Co)] was several times higher than that of free or Cu-chelated PEP and was temperature independent. A double reciprocal plot of the data demonstrated both saturable (K_m = 4.5 μM, V_max = 1.3 × 10^?18 mole/min/cell) and non-saturable components of the uptake of PEP(Co). The saturable component was inhibited specifically by cobalt chelated bleomycin analogs. PEP-chelates with metals other than cobalt, such as PEP(Cu) were metabolically unstable. These results suggest that bleomycin enters into cells as a metal chelate through a specific transport site.     

Divalent metals inhibit and lactose stimulates zinc transport across brush border membrane vesicles from piglets

Interactions between metals of similar coordination chemistry are of relevance to infant nutrition due to the highly variable metal:metal ratios found in formulas. Using ratios similar to those found in infant formulas, our objectives were to determine the effects of metals and of lactose and other saccharides on Zn(+2) transport across intestinal brush border membranes. Brush border membrane vesicles prepared from intestines of 5 preweaned piglets were used to determine whether Ca(+2), Mg(+2), Fe(+2), Cu(+2), Cd(+2), or Mn(+2) would antagonize Zn(+2) uptake. (65)Zn(+2) uptake by brush border membrane vesicles was measured over 20 min with metal concentrations constant, and at 1 min with increasing metal concentrations. Zn(+2) bound to the external surface of vesicles was removed with ethylenediamine-tetraacetic acid. Lactose induced Zn(+2) uptake to a greater extent than glucose polymer, whereas maltose, galactose, or galactose/glucose had no effect. Over 20 min, a 10:1 concentration of Fe(+2), Cd(+2), Cu(+2), and Mn(+2) lowered Zn(+2) uptake significantly (P < 0.05). Higher concentrations of divalent cation significantly lowered Zn(+2) (0.2 or 0.1 mM) uptake for all metals tested (P < 0.05), except for Mn(+2) (0.1 mM Zn(+2)). Inhibition constant determination quantified relative competitive potential with Mg(+2) < Ca(+2) < Mn(+2) < Fe(+2) < Zn(+2) < Cu(+2). Relative amounts of Ca(+2), Mg(+2), and Fe(+2) similar to those found in infant formulas reduced Zn(+2) uptake by at least 40%. Our data demonstrate that dietary minerals compete during brush border membrane transport, and may help explain antagonistic mineral interactions observed in vivo. Divalent metal concentrations and lactose content of milk affect zinc absorption in neonates and must be carefully considered in formula design.     

Zinc deficiency as a critical problem in wheat production in Central Anatolia

In a soil and plant survey, and in field and greenhouse experiments the nutritional status of wheat plants was evaluated for Zn, Fe, Mn and Cu in Central Anatolia, a semi-arid region and the major wheat growing area of Turkey.All 76 soils sampled in Central Anatolia were highly alkaline with an average pH of 7. 9. More than 90% of soils contained less than 0.5 mg kg^-1 DTPA-extractable Zn, which is widely considered to be the critical deficiency concentration of Zn for plants grown on calcareous soils. About 25% of soils contained less than 2.5 mg kg^-1 DTPA-extractable Fe which is considered to be the critical deficiency concentration of Fe for plants. The concentrations of DTPA-extractable Mn and Cu were in the sufficiency range. Also the Zn concentrations in leaves were very low. More than 80% of the 136 leaf samples contained less than 10 mg Zn kg^–1. By contrast, concentrations of Fe, Mn and Cu in leaves were in the sufficient range.In the field experiments at six locations, application of 23 kg Zn ha^-1 increased grain yield in all locations. Relative increases in grain yield resulting from Zn application ranged between 5% to 554% with a mean of 43%. Significant increases in grain yield (more than 31%) as a result of Zn application were found for the locations where soils contained less than 0.15 mg kg^-1 DTPA-extractable Zn.In pot experirnents with two bread (Triticum aestivum, cvs. Gerek-79 and Kirac-66) and two durum wheats (Triticum durum, cvs. Kiziltan-91 and Kunduru-1149), an application of 10 mg Zn kg^-1 soil enhanced shoot dry matter production by about 3.5-fold in soils containing 0.11 mg kg^-1 and 0.15 mg kg^-1 DTPA-extractable Zn. Results from both field observations and greenhouse experiments showed that durum wheats were more susceptible to Zn deficiency than the bread wheats. On Zn deficient soils, durum wheats as compared to bread wheats developed deficiency symptoms in shoots earlier and to a greater extent, and had lower Zn concentration in shoot tissue and lower Zn content per shoot than the bread wheats.The results presented in this paper demonstrate that (i) Zn deficiency is a critical nutritional problem in Central Anatolia substantially limiting wheat production, (ii) durum wheats possess higher sensitivity to Zn deficient conditions than bread wheats, and (iii) wheat plants grown in calcareous soils containing less than 0.2 mg kg^-1 DTPA-extractable Zn significantly respond to soil Zn applications. The results also indicate that low levels of Zn in soils and plant materials (i.e. grains) could be a major contributing factor for widespread occurrence of Zn deficiency in children in Turkey, whose diets are dominated by cereal-based foods.     

Biofertilizers and/or some micronutrients role on wheat plants grown on newly reclaimed soil

Pot experiment was conducted to study the effect of biofertilizers (inoculation with different bacterial isolates), foliar spraying with some micronutrients (Mn, Zn, Fe and Mn+Zn+Fe) and their interaction on growth, physiological parameters and nutrients content of wheat plants grown on reclaimed soil. Pot experiment was conducted in the greenhouse of National Research center, The experimental design was split plot with four replicates. Four biofertilizer treatments (un‐inoculated, Bacillus polymyxa, Azotobacter chroococcum or Azosprillium barasilense) were used and randomly distributed in the main pots. The foliar treatments with micronutrients were randomly distributed in the sub plots. The growth parameters (plant height, leaf area, roots, shoots and whole plant dry weights and number of tillers & leaves per plant); some physiological parameters (soluble sugar %, protein %, polysaccharide %, chl. A+b μg cm^?1 leaf per plant, carotenoids μg g^?1, IAA mg kg^?1 and psll mol DCPIP reduced per mg chl. per h) and nutrient contents (N, P, K, Mg, Mn, Zn and Cu) of wheat plants were significantly increased by inoculating wheat grains with different bacteria as compared with un‐inoculated plants (control). The highest values of all the mentioned parameters were obtained by using Azospirillum brasilense followed by Azotobacter chroococcum and Bacillus polymyxa in decreasing order. Foliar spraying treatments significantly increased the growth parameters, physiological parameters as well as nutrients content of wheat plants as compared with control. Highest values were obtained by using (Mn+Fe+Zn) treatment followed by Zn, Fe and Mn in decreasing order. Micronutrients in wheat plants differed as the foliar treatments were differed, so application of any micronutrient individually significantly increased its content and enhanced the content of other micronutrients in wheat. Interaction between the used biofertilizers and foliar spraying with micronutrients significantly affected all the studied parameters of wheat plants, the highest were obtained by inoculating wheat grains with Azospirillum brasilense and spraying the plants with (Mn+Fe+Zn) treatment, while the lowest values were attained by un‐inoculated grains (control) and spraying the wheat plants with tap water (control). Effective microorganisms in combination with micronutrients could be recommended to farmers to lead higher wheat yield.     

Phloem translocation of Fe,Cu, Mn,and Zn in Ricinus seedlings in relation to the concentrations of nicotianamine,an endogenous chelator of divalent metal ions,in different seedling parts

During the first 8 days of germination the Ricinus seedling is supplied with all nutrients by the endosperm via phloem transport. In 4- to 8-days-old seedlings the concentrations and contents of Fe, Cu, Mn and Zn, and nicotianamine (NA) in the endosperm, cotyledons, hypocotyl and roots were estimated. From the data obtained translocation rates and flow profiles for the metals were established. The main sink for Fe, Mn and Zn were the cotyledons whereas Cu was mainly imported into the hypocotyl. Maximum flow rates occurred between days 5 and 7, for Zn between days 6 and 8.The time kinetics of NA and divalent metal ion concentrations and contents are interpreted as co-transport. The role of NA as transport vehicle of micronutrients in the sieve tubes is discussed.     

Zinc,Iron, Manganese and Copper Uptake Requirement in Response to Nitrogen Supply and the Increased Grain Yield of Summer Maize

The relationships between grain yields and whole-plant accumulation of micronutrients such as zinc (Zn), iron (Fe), manganese (Mn) and copper (Cu) in maize (Zea mays L.) were investigated by studying their reciprocal internal efficiencies (RIEs, g of micronutrient requirement in plant dry matter per Mg of grain). Field experiments were conducted from 2008 to 2011 in North China to evaluate RIEs and shoot micronutrient accumulation dynamics during different growth stages under different yield and nitrogen (N) levels. Fe, Mn and Cu RIEs (average 64.4, 18.1and 5.3 g, respectively) were less affected by the yield and N levels. ZnRIE increased by 15% with an increased N supply but decreased from 36.3 to 18.0 g with increasing yield. The effect of cultivars on ZnRIE was similar to that of yield ranges. The substantial decrease in ZnRIE may be attributed to an increased Zn harvest index (from 41% to 60%) and decreased Zn concentrations in straw (a 56% decrease) and grain (decreased from 16.9 to 12.2 mg kg⁻¹) rather than greater shoot Zn accumulation. Shoot Fe, Mn and Cu accumulation at maturity tended to increase but the proportions of pre-silking shoot Fe, Cu and Zn accumulation consistently decreased (from 95% to 59%, 90% to 71% and 91% to 66%, respectively). The decrease indicated the high reproductive-stage demands for Fe, Zn and Cu with the increasing yields. Optimized N supply achieved the highest yield and tended to increase grain concentrations of micronutrients compared to no or lower N supply. Excessive N supply did not result in any increases in yield or micronutrient nutrition for shoot or grain. These results indicate that optimized N management may be an economical method of improving micronutrient concentrations in maize grain with higher grain yield.     

Iron transport mechanisms in reticulocytes and mature erythrocytes

The mechanism of iron transport into erythroid cells was investigated using rabbit reticulocytes and mature erythrocytes incubated with ⁵⁹Fe-labelled Fe(II) in isotonic sucrose or in solutions in which the sucrose was replaced with varying amounts of isotonic NaCl or KCl. Iron uptake was inhibited at all concentrations of NaCl, in a concentration-dependent manner, but with KCl inhibition occurred only at concentrations up to 10 mM. Higher KCl concentrations stimulated iron uptake to the cytosol of the cells, but inhibited its incorporation into heme. This effect became more marked as the iron concentration was raised. It was found that KCl inhibits iron incorporation into heme and stimulates iron uptake by mature erythrocytes, as well as by reticulocytes. It is concluded that erythroid cells can take up nontransferrin-bound Fe(II) by two mechanisms. One is a high-affinity mechanism that is limited to reticulocytes, saturates at a low iron concentration, and is inhibited by metabolic inhibitors. The other is a low-affinity process that is found in both reticulocytes and erythrocytes, becomes more prominent at higher iron concentrations, and is stimulated by KCl, as well as RbCl, LiCl, CsCl, and choline Cl. The KCl stimulation is inhibited by amiloride, but not by metabolic inhibitors, and its operation is not dependent on changes in cell volume or membrane potential, but it does require the presence of a permeant extracellular anion. Iron uptake by this process appears to occur by facilitated transport and is possibly assoicated with exchange of Na⁺. A further aspect of this study was a comparison of iron uptake by reticulocytes from Fe(II)-sucrose and Fe(II)-ascorbate using a variety of incubation conditions. No major differences were observed. © 1995 Wiley-Liss, Inc.