Distribution and Utilization of 15N in Cowpeas Injected into the Stem Under Influence of Water Deficit

Abstract

Investigations were carried out on Vigna unguiculata L. Walp. to estimate the distribution and utilization of ¹⁵N in different organs after stem injection during vegetative, flowering and pod filling stage. During flowering effects of water deficit were also examined. In well watered plants, within 4 days after injection, 65% of ¹⁵N accumulated in leaves. This was drastically reduced to 42% by water deficit. ¹⁵N accumulation in stems increased under water deficit. The translocation of ¹⁵N from the stem base to roots were not altered by water deficit. During pod filling 62% of recovered ¹⁵N in the plants had accumulated in seeds, 24% in leaves and 11% in stems within 4 days, whereas the uptake of nitrogen in pod walls and roots remained low (2%). These results demonstrate that the method of injecting very small quantities (1 mg/plant) of ¹⁵N into the stem base allows an exact and detailed quantitative assessment of N translocation/distribution with regard to different organs, different growth stages and different treatments.     

转小鼠金属硫蛋白(MT)基因烟草不同器官中金属离子铅和锌的分布

转金属硫蛋白(MT)基因植物具有清除重金属污染的能力,但是金属离子在植物体内的分布研究较少。文章以多代培育纯合的转MT烟草为材料,研究了转MT基因烟草积累铅和锌以及铅和锌在不同器官的分布情况。结果表明转基因植株的老叶、茎部和根部铅和锌积累量显著高于普通烟草植株,整株的铅和锌含量分别提高了21.8%和27.2%。铅和锌在植物体内的分布也发生了变化,转基因植株老叶和根中的铅含量分别高出普通烟草同位置的30.2%和47.8%,锌在转基因植株老叶、茎和根中的含量分别高出普通烟草同位置的44.7%,29.2%和21.6%,说明铅更容易在转基因植株老叶和根中积累,而锌更容易在转基因植株的老叶和茎中积累。     

Nitrogen fixation and nitrogen fertilization of soybeans

Abstract In pot experiments with (15)N labelled soil and mineral (15)N, the influence of Bradyrhizobium (Rhizobium japonicum) inoculation and N fertilization on the symbiotic N(2) fixation and yield of soybeans [Glycine max (L.) Merill., cv. 'Fiskeby V'] was investigated. Symbiotic N(2) fixation only occured after inoculation with Bradyrhizobium. Considerable differences in efficiency of the bacterial preparations were observed. Shortly after flowering, the symbiotic nitrogen fixation was finished and, subsequently, soybeans took up considerable N amounts from the soil. N fertilization at seeding suppressed N(2) fixation of soybeans. In this case, the dry matter and nitrogen yield increased, because the loss of fixed nitrogen was overcompensated by the mineral N uptake. During flowering of soybeans, the N(2) fixation was not affected by N supply, because this process was already terminated. The mineral N was additionally available to the plants and led to increased N amounts in plants. It was absorbed to a considerable degree by soybeans. The mineral N was translocated (partly, after intermediate storage in the vegetative organs) into the seeds thus increasing their yields.     

Relationships between Nitrogen Translocation and Accumulation in Growing Plant Parts of Grain Legumes

Abstract

Grain legumes absorbed mineral ¹⁵N at every stage of development and transported it directedly (just as symbiotically fixed ¹⁵N₂) into the plant parts growing at the respective stage. The ¹⁵N accumulation in the grains after long-lasting ¹⁵N supply can be ascribed, for the major part, to a secondary ¹⁵N translocation after a temporary incorporation into older plant parts (leaves, stem). Inhibition experiments with antibiotics revealed no direct relation between the accumulation of amino acid ¹⁵N in growing pods and seeds and the protein synthesis in this target organs. It may include, however, processes of (active ?) uptake and transport with a possible contribution of carrier systems specific for distinct amino acids.     

Deposition of 15N into Soil Layers of Different Proximity to Roots by Wheat Plants

Abstract

The translocation of root borne N compounds to different distances from the roots was studied by use of rectangular pots with three separated soil zones. Wheat plants were grown for 28 days (4 leaf stage) and subsequently pulse labelled by exposure to 15 ppm ¹⁵NH₃ (generated from (¹⁵NH₄)₂SO₄ with 95 at.-% ¹⁵N exc.) every other day with the rooting medium sealed from the atmosphere. Six pulses were applied in total.

The plants assimilated 65% of the label offered. The final ¹⁵N enrichment in the shoots was approx. 13 at.-% exc. and in the roots approx. 5 at.-% exc. These abundances were high enough to detect traces of ¹⁵N in soil approximately 1 cm distant from the roots. Most of the ¹⁵N recovered was retained in the shoots (about 90%), 5% were present in the roots and another 5% had been released into the rhizosphere. Considering the ¹⁵N released, 62% were found in the central root zone, 26% in the adjacent layer and 12% in the outer zone.     

Tracking iron oxide nanoparticles in plant organs using magnetic measurements

Common bean plants were grown in soil and irrigated with water solutions containing different concentrations of \(\hbox{Fe}_3\hbox{O}_4\) nanoparticles (NPs) with a mean diameter close to 10 nm. No toxicity on plant growth has been detected as a consequence of Fe deficiency or excess in leaves. In order to track the \(\hbox{Fe}_3\hbox{O}_4\) NPs, magnetization measurements were performed in soils and in three different dried organs of the plants: roots, stems, and leaves. Some magnetic features of both temperature and magnetic field dependence of magnetization M(T, H) arising from \(\hbox{Fe}_3\hbox{O}_4\) NPs were identified in all the three organs of the plants. Based on the results of saturation magnetization \(M_\mathrm{s}\) at 300 K, the estimated number of \(\hbox{Fe}_3\hbox{O}_4\) NPs was found to increase from 2 to 3 times in leaves of common bean plants irrigated with solutions containing magnetic material. The combined results indicated that M(T, H) measurements, conducted in a wide range of temperature and applied magnetic fields up to 70 kOe, constitute a useful tool through which the uptake, translocation, and accumulation of magnetic nanoparticles by plant organs may be monitored and tracked.     

15N allocation into wheat grains (Triticum aestivum L.) influenced by sowing rate and water supply at flowering under a Mediterranean climate

This study examined the effects of a reduced wheat sowing rate (250 vs. 500 grains m^–2) on grain yield, uptake of ¹⁵N into grains, and the incorporation into gluten and non-gluten proteins of wheat under field conditions in the Aegean region. A single ¹⁵N application was applied at stem elongation, at flowering, or at both developmental stages. Each ¹⁵N treatment included either additional water supply, or no additional water supply at flowering. Sowing rate (either 250 or 500 grains m^–2) had no impact on grain yield. Grain yield increased with additional water supply, but at the expense of protein quality, because of a decrease in the protein content of gluten. The ¹⁵N content of the gluten and non-gluten proteins at grain maturity was not different among cultivars. ¹⁵N applied at both stem elongation and flowering was found in comparable amounts in grains and protein fractions, irrespective of sowing rate.     

Chromium localization in plant tissues of Lycopersicum esculentum Mill using ICP-MS and ion microscopy (SIMS)

High-resolution imaging secondary ion mass spectrometry (HRI-SIMS) in combination with inductively coupled plasma mass spectrometry (ICP-MS) were utilised to determine specific sites of chromium concentration in tomato plant tissues (roots, stems and leaves). The tissues were obtained from plants grown for 2 months in hydroponic conditions with Cr added in a form chromium salt (CrCl₃·6H₂O) to concentrations of 25 and 50 mg/L. The chemical fixation procedure used permit to localize only insoluble or strongly bound Cr components in tomato plant tissue. In this work no quantitative SIMS analysis was made. HRI-SIMS analysis revealed that the transport of chromium is restricted to the vascular system of roots, stems and leaves. No Cr was detected in epidermis, palisade parenchyma and spongy parenchyma cells of the leaves. The SIMS-300 spectra obtained from the tissues confirm the HRI-SIMS observations. The roots, and especially walls of xylem vessels, were determined as the principal site of chromium accumulation in tomato plants.     

Mapping of the metal intake in plants by large-field X-ray microradiography and preliminary feasibility studies in microtomography

This paper reports on dual energy micro-radiography and tomography techniques applied both to thin plant leaves treated with copper or lead solutions and on Cu-treated small roots and stem sections, performed at the SYRMEP X-ray beamline of ELETTRA synchrotron facility in Trieste (Italy). The features of the source allowed us to apply different imaging techniques with an extremely vast field of view, up to 160 ×6 mm2 and 28×6 mm2 for micro-radiography and tomography experiments, respectively. The feasibility of getting positive indications on metal accumulation in leaves, sections of roots and stems, stem and root whole cylindrical pieces has been checked.     

ICP-AES测定银条不同部位重金属含量

应用混合酸(HClO4∶HNO3=1∶4)在常压条件下对银条茎叶样品进行消解,采用电感耦合等离子体-原子发射光谱法(ICP-AES)测定了银条不同器官的6种重金属Fe、Zn、Mn、Cu、Cd和Pb含量。校准曲线的相关系数均在0.9998—1.0000之间,加标回收率在97.0%—108.9%之间,相对标准偏差为0.45%—3.20%,实验结果可靠。结果显示,银条叶片和地上茎中的重金属含量顺序均为FeZnMnCuPb、Cd,地下茎中的含量顺序为ZnFeCuMnCdPb;同种重金属元素符合叶片地上茎地下茎的规律(Cu除外),其中Fe元素在叶片中含量分别是地上茎和地下茎的4.11、5.35倍。说明银条地下茎部分是无污染、安全的特色蔬菜。     

Nitrogen stable isotope composition of leaves and roots of plants growing in a forest and a meadow

In controlled N-nutrition experiments, differences in delta15N composition of leaves and roots are regularly found. In this paper we report results from a survey of nitrogen stable isotope signatures of leaves and roots of 16 plant species growing under natural conditions in a meadow and a forest understorey, which differed in nitrate and ammonium availability. Significant differences between leaf and root were observed. The range of delta15N [leaf-root] values was -0.97 to +0.86 per thousand, small compared to published values from controlled N-nutrition experiment, but almost as large as the range of leaf delta15N values (-1.04 to +1.08 per thousand). Forbs showed the largest differences between leaves and roots and showed a significant difference with respect to habitat. Grasses and legumes did not show significant differences in delta15N [leaf-root] between the two habitats. Care must be taken when using leaf delta15N values as representative for whole-plant 15N composition in these two habitats.     

Potential for assessing long-term dynamics in soil nitrogen availability from variations in delta15N of tree rings

Numerous researchers have used the isotopic signatures of C, H, and O in tree rings to provide a long-term record of changes in the physiological status, climate, or water-source use of trees. The frequently limiting element N is also found in tree rings, and variation in its isotopic signature may provide insight into long-term changes in soil N availability of a site. However, research has suggested that N is readily translocated among tree ring of different years; such infidelity between the isotopic compositions of the N taken up from the soil and the N contained in the ring of that growth year would obscure the long-term N isotopic record. We used a 15-year 15N-tracer study to assess the degree of N translocation among tree rings in ponderosa pine (Pinus ponderosa) trees growing in a young, mixed-conifer plantation. We also measured delta13C and delta15N values in unlabeled trees to assess the degree of their covariance in wood tissue, and to explore the potential for a biological linkage between them. We found that the maximum delta15N values in rings from the labeled trees occurred in the ring formed one-year after the 15N was applied to the roots. The delta15N value of rings from labeled trees declined exponentially and bidirectionally from this maximum peak, toward younger and older rings. The unlabeled trees showed considerable interannual variation in the delta15N values of their rings (up to 3 and 5 per thousand), but these values correlated poorly between trees over time and differed by as much as 6 per thousand. Removal of extractives from the wood reduced their delta15N value, but the change was fairly small and consistent among unlabeled trees. The delta13C and delta15N values of tree rings were correlated over time in only one of the unlabeled trees. Across all trees, both delta13C values of tree rings and annual stem wood production were well correlated with annual precipitation, suggesting that soil water balance is an important environmental factor controlling both net C gain and transpirational water loss at this site. Our results suggest that interannual translocation of N among tree rings is substantial, but may be predictable enough to remove this source of variation from the tree-ring record, potentially allowing the assessment of long-term changes in soil N availability of a site.     

银沙槐不同部位中微量元素含量的测定

利用火焰原子吸收光谱法测定银沙槐的不同部位中Cu、Zn、Ca、Fe、Mg、K、Cr、Mn的含量。对银沙槐植物中的根、茎、叶、花、果实中金属元素的含量进行了分析比较。以此研究了这几种金属元素在银沙槐体内的分布。结果显示,各元素在实验范围内,线性关系良好,加标回收率在92.00%—107.00%之间。相对标准偏差在0.02%—5.80%之间。由实验结果发现,银沙槐的不同部位中Cu、Zn、Ca、Fe、Mg、K、Cr、Mn的含量有差异。     

Distribution of Externally Applied 15NH4 + or 15NO3 − in White Lupins at Different Developmental Stages

White lupins (Lupinus albus L., var. Kievsky mutant) were grown in Mitscherlich pots. ¹⁵NH₄NO₃ or NH₄ ¹⁵NO₃ (10 or 95 at% ¹⁵N exc.) was applied at the late vegetative stage (14–16 leaves) or at the generative stage (end of bloom), respectively. Dry weight increase (ΔDW) of the plants as well as the ¹⁵N distribution in different organs and N fractions (NO_{3 ?}-N, NH₂-N, protein N) were investigated after 5 days and 50 days (maturity). The following results were obtained:

1. In comparison with the ¹⁵N derived from NO₃ ^?, the ¹⁵N derived from NH₄ ⁺ was more strongly retained in the roots. When transported into the shoot, it was more strongly translocated into the tip.

2. More ¹⁵N derived from NH⁴ ₊ was incorporated into proteins and reduced soluble N compounds than ¹⁵N derived from NO₄ ^?. Even in the above-ground plant tissues, a considerable proportion of the latter was found as NO₃ ^?.

3. In the long-term experiment (harvest at maturity 50 days after application), no difference in translocation and incorporation could be found between the two offered ¹⁵N sources.     

Effects of N-application on utilization of 15N and 13C and quality in two wheat cultivars

We studied N uptake and distribution in wheat, and the incorporation of nitrogen and carbon into gluten and non-gluten proteins using a double-labelling approach with 15N and 13C. Doses of N-fertilizer were split and applied at emergence, onset of stem elongation, and heading at rates of 280/140/140 mg N pot(-1), respectively simulating 90/45/45 kg N ha(-1). Five different combinations of N-fertilizations containing no or 10 % 15N were performed. The recovery of 15N added at the stages emergence, stem elongation or heading were 42, 60, and 64 %. Application of 15N at all three stages yielded in 51 % recovery. Remobilisation of straw N was greater for Golia. The 15N concentration in gluten proteins of Golia show higher values than Gonen. The ratio of 15N gluten/15N non-gluten proteins of Golia were higher, which implies a lower non-gluten protein activity during grain filling. The 13C concentration in gluten and non-gluten proteins did not differ between both cultivars.     

X‐ray absorption spectroscopy at the Ni?K edge in Stackhousia tryonii Bailey hyperaccumulator

Young plants of Stackhousia tryonii Bailey were exposed to 34 mM Ni kg^?1 in the form of NiSO₄· 6H₂O solution and grown under controlled glasshouse conditions for a period of 20 days. Fresh leaf, stem and root samples were analysed in vivo by micro x‐ray absorption spectroscopy (XAS) at the Ni? K edge. Both x‐ray absorption near edge structure and extended x‐ray absorption fine structure spectra were analysed, and the resulting spectra were compared with spectra obtained from nine biologically important Ni‐containing model compounds. The results revealed that the majority of leaf, stem and root Ni in the hyperaccumulator was chelated by citrate. Our results also suggest that in leaves Ni is complexed by phosphate and histidine, and in stems and roots, phytate and histidine. The XAS results provide an important physiological insight into transport, detoxification and storage of Ni in S. tryonii plants. Copyright © 2008 John Wiley & Sons, Ltd.     

Spectral Investigation of Phosphorus Compounds in Spinacia Oleracea Using Fourier Transform Infrared Method

The study uses the Fourier transform infrared spectroscopy method to evaluate the influence of phosphogypsum from the soil on the growth and accumulation of nutrients in Spinacia oleracea. Attenuated total reflectance spectra of Spinacia oleracea roots and stems originated from plants cultivated on 28% to 52% phosphogypsum enriched soil have been studied in the 4000–600 cm^?1 area. The structure of the infrared absorption bands for spinach roots and stems and for the soil where plants were grown was analyzed. Thus, it was observed that phosphorus–oxygen bonds contribution can be identified both in roots and stems absorption spectra. The significance of the research is the possibility to use the infrared investigation as rapid technique, particularly useful for agriculture, to study the extraction and assimilation process of the compounds containing phosphorus and nitrogen from the soil in which the spinach seedlings grew. In the case of this study, it was observed that the absorption of phosphorus in the spinach roots and stems has not the same effect. The analysis of obtained data indicated that the assimilation of phosphorus from phosphogypsum enriched soil induces changes in spinach roots structure that are most likely due to an increase synthesis of proteins, rather than to a decrease in carbohydrates quantity.     

Isotopic study of post-anthesis foliar incorporation of sulphur and nitrogen in wheat

Nitrogen (N) and sulphur (S) supplies have a strong influence on the quality and quantity of wheat storage proteins, which play an important role in the bread-making process. In order to relate the incorporation and distribution of foliar N and S fertilisers at the post-anthesis stage to the quality of wheat, 15N and 34S isotopes were used as tracers. The incorporation of these tracers in different plant parts (leaves, stems, ears) and in each storage protein fraction (gliadins, HMW and LMW glutenin subunits) was determined by isotopic ratio mass spectrometry coupled with an elemental analyser (EA-IRMS). By this means, the true recovery coefficient of N and S (TRCNfertiliser and TRCSfertiliser) and the N and S derived from fertilisers (Ndff and Sdff) could be determined. The TRCNfertiliser and TRCSfertiliser values of the different plant parts provide evidence of the applied N and S assimilation and translocation from wheat leaves to the seeds. The determination of Ndff and Sdff incorporated into storage proteins shows the efficiency and the influence of N and S incorporation into each storage protein fraction. Moreover, a favourable stage for fertiliser application can be determined by the TRCNfertiliser values in the grain and in the whole plant. The fertilisers enriched in stable isotope used in the culture techniques can be a means of understanding the effectiveness of fertilisers in the expression of wheat quality.     

Water Deficit and Salt Stress Diagnosis Through LED Induced Chlorophyll Fluorescence Analysis in Jatropha curcas L.

LED induced chlorophyll fluorescence analysis is employed to investigate the effect of water deficit and salt stress upon the growth process of Jatropha curcas L.. Red(Fr) and far-red(FFr) chlorophyll fluorescence around 685 nm and 735 nm, respectively, were observed and examined as a function of the stress intensity(salt concentration and water deficit). The fluorescence ratio Fr/FFr which is a valuable nondestructive and nonintrusive indicator of the chlorophyll content of leaves was exploited to monitor the jatropha plants under stress. The data indicated that salinity plays a minor role in the chlorophyll concentration of leaves for NaCl concentrations in the 25 to 200 mM range. The fluorescence ratio also permitted the detection of damage caused by water deficit in the early stages of the plants growing process. A significant variation of the Fr/FFr ratio was observed in the first 10 days of the experiment, and before signs of visual stress became apparent. The results suggest that the Fr/FFr ratio is an early-warning indicator of water deficit stress     

美洲商陆对锰毒生理响应的FTIR研究

在一定Mn浓度梯度处理下(0,0.125,0.25,0.5,1 g·kg-1),超积累植物——美洲商陆(Phytolacca americana)不同组织器官的傅里叶变换红外光谱(FTIR)图谱发生了变化。其中,茎组织在3 336和2 916 cm-1处峰高先上升后下降,反映了有机物运输受阻情况的变化,即美洲商陆在低Mn刺激下会产生大量有机物作为渗透调节物质来增强其耐Mn性,高Mn则抑制了有机物的分泌和运输;根和叶组织分别在2 922和1 606 cm-1处表现不同变化趋势,但都反映了一个变化规律即低Mn处理下美洲商陆分泌的有机酸不断螯合Mn,随着Mn毒害的加重,其羧酸螯合力变弱;根组织1 732和1 026 cm-1、茎组织1 028 cm-1、叶组织1 052和967 cm-1处呈现差异性变化,但都与其膜脂过氧化有关;根组织1 375 cm-1处峰高先上升后下降,可能与植物在细胞壁结构上增强抗逆性有一定关系,即低Mn处理下细胞壁可能通过阳离子交换能力(CEC)的提高增强了耐Mn性。以上说明,利用FTIR研究重金属超积累植物化学组分具有应用价值。