The uptake and the transport of14C-labeled epibrassinolide in intact seedlings of cucumber and wheat

The uptake and the transport of exogenously applied epibrassinolide (EBR) in seedlings of cucumber and wheat were examined by autoradiography using¹⁴C-EBR.¹⁴C-EBR was applied to roots, young and mature leaves, and the shoot apex. When applied to roots,¹⁴C-EBR was readily taken up and was swiftly transported throughout both plant species. When¹⁴C-EBR was applied to the adaxial surface of a young cucumber leaf, it was readily taken up, but was very slowly transported. In cucumber leaves,¹⁴C-EBR was transported throughout the treated leaf after 3 days of treatment, and then it was transported to upper leaves from the treated leaf after 7 days. Some 6.3% of applied¹⁴C-EBR was transported to the newly expanded leaves. In wheat leaves,¹⁴C-EBR was transported only in the apical direction from the treated spot after 3 days of treatment, but it was not transported from the treated leaf to the other leaves or organs even after 7 days. Some 1.3% of applied¹⁴C-EBR was transported to the tip area of the treated leaf. These results indicate that exogenous EBR applied to intact plants is acropetally transported.     

Distribution of labelled assimilates within a young apple tree after supplying14CO2to a leaf or shoot

Labelled carbon dioxide was supplied for 22 hrs to a leaf of the leader or to the lateral shoot in two-year-old apple seedlings. The distribution of radioactive assimilates within the plant following this treatment was investigated by using radioautography. The transport of labelled assimilates from the young leaf of the leader was very meagre and affected only parts of the stem and the leaves situated in the close vicinity of the treated leaf. The¹⁴C-labelled assimilates from the mature leaf of the leader were transported in a considerable amount to the apex and to the other leaves of the leader. They were also found in an appreciable amount in the stem and the roots, as well as in some lateral shoots. After supplying¹⁴CO₂ to the lateral shoot remarkable transport of labelled assimilates was observed. Radioactivity was detected in the tip and in the youngest leaves of the leader, as well as in the roots. Their path in the stem was studied by dissecting the plant and examining the cross section from each internode. This method revealed that the assimilates from the treated leaf or shoot were transported downward only on one side of the stem in a helical pattern. The lateral shoots situated on the radioactive side of the stem were also labelled, whereas those situated on the opposite (non-radioactive) side were not labelled.     

The uptake and transport of silicon by perennial ryegrass and wheat

Summary In experiments with perennial ryegrass and wheat, silicon (Si) concentration in flowing solution culture was maintained constant at 0, 10 and 20 mgl⁻¹ (ryegrass) or 0, 20 and 40 mgl⁻¹ (wheat). Uptake and transport were measured in both species at frequent harvests over periods of up to 80 days. By the final harvests the initial differences in concentration between plants grown at high or low Si were largely eliminated. Much more Si was taken up by both species from the culture solution than was present in the transpiration stream. With ryegrass, the calculated cumulative amounts taken up through mass flow by plants grown at 10 or 20mgl⁻¹ Si, represented less than 40 and 70 per cent, respectively, of the total Si uptake. Up to 94 per cent of the Si taken up by wheat was transported rapidly to the shoots; older leaves contained up to 11.8 per cent Si.     

The uptake by plants of polymaleic acid: A polycarboxylic acid structurally related to those of soils

Summary The uptake of¹⁴C labelled polymaleic acid (PMA) by tomato and wheat plants cultured under axenic conditions was estimated during 48 d growth for tomato and 17 d for wheat seedlings. The concentrations of PMA, calculated from¹⁴C data, reached values of over 1 mg g⁻¹ FW for root tissue and over 0.2 mg g⁻¹ FW for shoots. Freeze-dried roots were shown to take up a substantial amount of PMA over short periods demonstrating a major non-metabolic adsorption. PMA was adsorbed by carboxymethyl cellulose, used as a model system for plant roots, in amounts comparable with freeze-dried roots. The adsorptive capacity of carboxymethyl cellulose was increased by treatment with solutions of metal ions. Especially effective in this respect were Cu, Fe and Al. It is suggested that at least two mechanisms are involved in the adsorption of PMA by polysaccharides and by plant roots. One, possibly hydrogen bonding, being independent of the presence of metal ions and another depending on the presence of multivalent cations.     

Reduction and transport of Fe from siderophores

Soils contain siderophores produced by bacteria and fungi; however, the role of siderophores in Fe nutrition of plants is uncertain. The Strategy I plant cucumber (Cucumis sativus L.) was used in an investigation of ferric chelate reduction activity and uptake and transport of Fe from ferric hydroxyethylethylenetriacetic acid (FeHEDTA) and ferric N,N–di–(2–hydroxybenzoyl)–ethylenediamine– N,N-diacetic acid (FeHBED) and the hydroxamate siderophores, ferric rhodotorulic acid (FeRA) and ferric ferrioxime B (FeFOB). Cucumber seedlings were grown in a hydroponic medium without Fe or supplied with 10 M FeHEDTA. Iron-deficient cucumber roots readily reduced FeHEDTA, while Fe-sufficient roots had low levels of ferric chelate reduction activity. The siderophore FeRA was reduced by Fe-deficient roots at 8% of the rate of FeHEDTA, while FeFOB was not reduced. The highly stable synthetic chelate FeHBED was reduced at 16% the rate of FeHEDTA. Fe transport to shoots by Fe-deficient seedlings from the slowly reducible complexes ⁵⁹FeRA and ⁵⁹FeHBED was, respectively, 74% and 73% of that transported from ⁵⁹FeHEDTA. The ferrous complexing agent, bathophenanthrolinedisulfonic acid (BPDS), had a strong inhibitory effect on uptake and transport of Fe from ⁵⁹FeHEDTA or ⁵⁹FeRA into shoots. An average of 11% as much Fe was transported to shoots of Fe-deficient seedlings from ⁵⁹FeFOB as from ⁵⁹FeHEDTA. Neither the Fe nutritional status of the seedlings nor the presence of BPDS influenced the uptake and transport of Fe from ⁵⁹FeFOB. It is concluded that cucumber roots may take up substantial amounts of Fe from FeRA and FeHBED following reduction, while small amounts of Fe may be taken up from FeFOB by a mechanism not involving reduction of the ferric siderophore at the root surface.     

Phosphorus transport to the xylem and its regulation by water flow

Summary The effects of water flow on phosphorus uptake by roots and on its subsequent translocation to shoots were separated by giving short-term pulses of ³²P-labelled nutrient to intact tomato plants. At the end of a 5 min pulse, all the ³²P taken up by the plants was confined to the roots. Only about half of this ³²P was later translocated to shoots; there was very little translocation after 4 hours.Experiments after long-term labelling showed that only a small part of the total P in the root is readily translocated to shoots. This P appears to be in part of the symplast and contributes about 75% of the P transported to the xylem sap. The rest is presumably derived by leakage from vacuoles.A slow rate of water flow reduced both uptake into the symplast and the translocation to the shoots of P which had already been absorbed by the roots. This was conclusively demonstrated by giving a ³²P pulse before reducing the rate of water flow; ³²P not translocated to shoots was partly retained by the roots and partly lost to the external solution. Water flow also accelerates transport to the xylem of previously-absorbed P in excised roots.It is concluded that the major effect of water flow on phosphorus transport to shoots occurs after phosphorus uptake by the roots, probably during radial transport to the xylem.     

Uptake of mannitol from the media by in vitro grown plants

Higher plants grown in vitro are very seldom fully autotrophic. Therefore, such cultures are usually supplied with exogenous sugars. However, at higher sugar concentration a decrease in dry matter accumulation is observed which can be explained by a decrease in osmotic potential of the medium.To test this explanation a series of experiments with mannitol, a sugar alcohol often used for simulation of osmotic stress, were performed with excised wheat embryos, rape seedlings and potato stem segments grown in vitro. As the presence of mannitol in the medium caused a significant decrease in dry matter accumulation, the content of mannitol in the shoot tissues was determined using HPLC analysis to estimate the uptake and transport of mannitol from roots to shoots. Mannitol contents up to 30% of dry weight in wheat and 20% in rape and potato shoots were found, indicating that mannitol is easily taken up by in vitro plants and transported to shoots. There were no large changes in the content of glucose, fructose and sucrose caused by the presence of mannitol in the tissues. These data show that mannitol can not be used as an inert osmoticum in in vitro studies.     

Application of X-ray absorption near edge spectroscopy to the study of the effect of sulphur on selenium uptake and assimilation in wheat seedlings

Selenium (Se) is an essential trace element for humans and animals. A hydroponic experiment was performed to study the effects of sulphur (S) on Se uptake, translocation, and assimilation in wheat (Triticum aestivum L.) seedlings. Sulphur starvation had a positive effect on selenate uptake and the form of Se supplied greatly influenced Se speciation in plants. Compared with the control plants, Se uptake by the S-starved plants was enhanced by 4.81-fold in the selenate treatment, and selenate was readily transported from roots to shoots. By contrast, S starvation had no significant effect on selenite uptake, and selenite taken up by roots was rapidly converted to organic forms and tended to accumulate in roots. X-ray absorption near edge spectroscopy (XANES) analysis showed that organic forms of selenium, including selenocystine, Se-methyl-selenocysteine (MeSeCys), and selenomethionine-Se-oxide, were dominant in the plants exposed to selenite and accounted for approximately 90 % of the total Se. Whereas selenate remained as the dominant species in the roots and shoots exposed to selenate, with little selenate converted to selenite and MeSeCys. Besides, sulphur starvation increased the proportion of inorganic Se species in the selenate-supplied plants, but had no significant effects on Se speciation in plants exposed to selenite. The present study provides important knowledge to understand the associated mechanism of Se uptake and metabolism in plants.     

Effects of shoot bending of apple trees on accumulation and translocation of14C-labelled assimilates

The translocation of¹⁴C-labelled assimilates from a single leaf in bent and intact apple shoots was studied in varying stages of shoot development. In actively growing shoots¹⁴C-labelled assimilates translocated from the treated leaf and accumulated mainly in the shoot apex. In moderately growing apple shoots radioactive assimilates were translocated from the treated leaf in both directions towards and down the shoot. In apple shoots showing only slight growth activity the¹⁴C-labelled assimilates were transported from the treated leaf mainly to the base of the shoot, stem and roots. Bending shoots changed the pattern of distribution of radioactive assimilates. Bending actively and moderately growing shoots resulted in higher concentration of 14-carbon in the shoot apex than in controls. In slowly growing and non-growing apple shoots bending caused a higher accumulation of radioactive assimilates in the bent section than in an equal section of control shoots.     

The responsiveness of the <Emphasis Type="Italic">IAA2</Emphasis> promoter to IAA and IBA is differentially affected in <Emphasis Type="Italic">Arabidopsis</Emphasis> roots and shoots by flavonoids

The structural features of flavonoids which are involved in the modulation of auxin distribution in Arabidopsis thaliana were evaluated. An auxin-inducible promoter IAA2 fused to a reporter gene (GUS) was used to monitor the tissue responsiveness to auxins. The following aspects were investigated: 1) the influence of flavonoids (quercetin, naringenin, kaempferol, myricetin and isorhamnetin) on the distribution of indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) in roots and leaves, 2) differences in flavonoid uptake into roots and shoots depending on flavonoid concentration in the medium, and 3) influence of structurally different flavonoids on the gravitropic response and growth of roots. The same flavonoids differently affected IAA and IBA distribution in leaves and roots. There were several structural requirements for the flavonoids which resulted in the changes of auxin response/distribution. Great differences between the ability of shoots and roots to take up quercetin were showed. Also, flavonoids influenced gravitropism and root growth of Arabidopsis seedlings in a structure-dependent manner.     

Effects of Low Root Temperature on Ion Uptake and Ion Translocation in Wheat

Roots of wheat seedlings (Triticum aestivum L. cv. Weibulls Starke) were cooled (+1°C) for 24 h while the shoots were kept at 25°C. The treatment induced an increased water deficit in the leaves. Fresh weight, dry weight, and the uptake and distribution of potassium and calcium were measured before and after cooling. Growth, measured both as fresh weight and dry weight increase, was reduced during the cold treatment. Afterwards (at 20°C), growth recovered to nearly pre-stress rates. Analysis of the potassium fluxes in and out of the roots by ⁸⁶Rb techniques showed that influx, and to a lesser extent efflux, were inhibited at low temperature. The result was a net potassium uptake rate of one-third that of unstressed plants. After the cooling period the potassium influx increased to the rate of control plants. The potassium efflux increased to one and one-half times the rate of unstressed wheat so that net uptake was negative. The increase in potassium efflux was explained by a higher permeability of the root cell membranes after cooling. The net uptake of calcium was reduced to one-third by root cooling. Contrary to potassium uptake, calcium uptake increased under post-stress conditions, partly due to a low efflux rate. During root cooling there was a redistribution of dry matter from the leaves down towards the lower part of the shoot. Afterwards the original distribution of dry matter was reestablished. The net flow of potassium and calcium followed a similar pattern as dry matter, suggesting a growth-regulated flow.     

Effects of root and foliar applications of exogenous NO on alleviating cadmium toxicity in lettuce seedlings

The effects of sodium nitroprusside (SNP, a donor of NO) on cadmium (Cd) toxicity in lettuce seedlings were studied. SNP was added into hydroponic systems or sprayed directly on the leaves of plants grown with and without Cd. Excess supply of Cd (100 μM) caused growth inhibition, dramatically increased Cd accumulation in both leaves and roots, and inhibited the absorption of Ca, Mg, Fe and Cu. Excess Cd also decreased activities of superoxide dismutase peroxidase and catalase in leaves and roots, and increased the accumulation of superoxide anion (O ₂ ^·? ), hydrogen peroxide (H₂O₂) and malondialdehyde (MDA). Root or foliar applications of exogenous NO alleviated Cd-induced growth suppression, especially root application of 250 μM SNP and foliar addition of 500 μM SNP. Addition of SNP promoted the chlorophyll synthesis suggesting that the photosynthesis was up-regulated. Exogenous NO increased Cd-decreased activities of antioxidant enzymes and markedly diminished Cd-induced reactive oxygen species (ROS) and MDA accumulation. Moreover, the absorption of Ca, Mg, Fe and Cu was increased, indicating that exogenous NO stimulated H⁺-ATPase activity to promote sequestration or uptake of ions. In addition, exogenous NO also inhibited Cd transfer from roots to shoots, which may indicate that Cd retention in roots induced by NO plays a significant role in Cd tolerance in lettuce seedlings. These data suggest that under Cd stress, exogenous NO improves photosynthesis by increasing chlorophyll synthesis, protects lettuce seedlings against oxidative damage by scavenging ROS, helps to maintain the uptake of nutrient elements, and inhibits Cd transferred to shoots effectively.     

镉引起小麦苗逆境乙烯的产生及其和镉的吸收分布的关系

溶液培养小麦幼苗转移至含Cd~(2 )的营养液中,根系乙烯产生较快地增加,约在12h达高峰,然后下降;ACC含量亦呈先升后降的趋势。未和Cd~(2 )溶液直接接触的地上部乙烯亦增加,至36h达高峰,此后急剧下降,而ACG和 MAGC含量持续上升。地上部乙烯的增加,主要是由通过根系运往地上部的镉直接作用的结果,不是根部合成ACG运往地上部后再产生的。电镜观察表明,地上部乙烯产生和ACC含量变化的时间进程,可以与镉进入叶细胞内的部位及其对细胞膜和细胞器的影响相联系。     

Interaction of phloem-translocated amino compounds with nitrate net uptake by the roots of beech (Fagus sylvatica) seedlings

In the present study two experimental approaches were used to investigate the influence of changes in the allocation of amino compounds in the phloem of beech (Fagus sylvatica L.) seedlings on nitrate net uptake by the roots. In a first set of experiments Gin or Asp were directly fed into the phloem of the epicotyl via bark flaps. These compounds were previously found to be allocated in the phloem of adult beech trees and were shown to inhibit nitrate net uptake when supplied to beech roots. Feeding of solutions containing 100 mM of Gin or Asp plus 10 mM EDTA into the phloem resulted in a significant enrichment of the fine root tissue with the amino compound fed as compared to the roots of control plants supplied with amino acid-free EDTA solutions. Nitrate net uptake by the roots decreased by 61% (Gin) and 79% (Asp) as compared to the controls. In a second approach, shoots of young beech seedlings were exposed to 40g NH3 m^-3. NH3 uptake by shoots, nitrate net uptake by roots, and the contents and composition of total soluble non-protein nitrogen (TSNN) in leaves, phloem, and fine roots were determined and were compared to results gained with control plants exposed to charcoal-filtered air. NH3 fumigation of the shoots of beech seedlings resulted in a 35% reduction of nitrate net uptake by the roots as compared to controls. TSNN contents in leaves and phloem exudate of NH3-fumigated plants increased by 56% and 37%, respectively. This enrichment was mainly due to Arg and Glu in the leaves and Asp, Asn, Glu, and Gin, but not to Arg, in phloem exudate. The TSNN content of the fine roots was not changed by NH3 fumigation, but a significant increase in the Gin content was observed. From these results it is concluded that phloem transport of amino compounds, especially of Gin and Asp, from the shoot to the roots mediates regulation of nitrate net uptake by the roots of beech trees in order to adapt this process to the nitrogen demand of the whole plant.     

Use of strontium isotopes and foliar K content to estimate weathering of biotite induced by pine seedlings colonised by ectomycorrhizal fungi from two different soils

Pinus sylvestris seedlings, colonised by ectomycorrhizal (EM) fungi from either of two different soils (untreated forest soil and a limed soil from a clear cut area), were grown with or without biotite as a source of K. The biotite was naturally enriched in ⁸⁷Sr and the ratio of ⁸⁷Sr/ ⁸⁶Sr in the plant biomass was estimated and used as a marker for biotite weathering and compared to estimates of weathering based on foliar content of K. Different nutrient regimes were used to expose the seedlings to deficiencies of K with and without an application of nitrogen (NH₄NO₃) in excess of seedling demand. The seedlings were grown for 220 days and the elemental composition of the shoots were analysed at harvest. The EM colonisation was followed by analysing the concentration of ergosterol in the roots and the soils. Bacterial activity of the soil was estimated by the thymidine incorporation technique. The concentration of organic acids in the soil solution was measured in the soil in which seedlings colonised by EM fungi from the untreated forest soil were grown. It was found that seedlings colonised by EM fungi from untreated forest soil had taken up more K in treatments with biotite addition compared to seedlings colonised by EM fungi from the limed forest soil (p<0.05). Seedlings from untreated forest soil had larger shoots and contained more K when grown with biotite compared to KCl as K source, indicating that biotite had a stimulatory effect on the growth of these seedlings which was not related to K uptake. Seedlings from the limed soil, on the other hand, had similar foliar K content when grown with either biotite or KCl as K source. The larger uptake of K in seedlings from untreated forest soil was not an effect of a more developed EM colonisation of the roots since seedlings from the limed soil had a higher ergosterol concentration both in the soil and in the roots. Nutrient regimes had no significant influence on the total uptake of K but the ⁸⁷Sr/ ⁸⁶Sr isotope ratio in the plant biomass indicated that seedlings grown with excess nitrogen supply had taken up proportionally less Sr from the biotite (1.8% of total Sr content) compared to seedlings grown with a moderate nitrogen supply (5.0%). Furthermore, seedlings grown with excess nitrogen supply had a reduced fungal colonisation of roots and soil and bacterial activity was lower in these soils. The ⁸⁷Sr/ ⁸⁶Sr ratio in the plant biomass was positively correlated with fungal colonisation of the roots (r ²=0.98), which may indicate that the fungus was involved in releasing Sr from the biotite. Uptake of K from biotite was not related to the amount of organic acids in the soil solution. Oxalic acid was positively related to the amount of ergosterol in the root, suggesting that oxalic acid in the soil solution originates from the EM symbionts. The accuracy of the estimations of biotite weathering based on K uptake by the seedlings in comparison with the ⁸⁷Sr/⁸⁶Sr isotope ratio measured in the shoots is discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Influence of external zinc and phosphorus supply on Cd uptake by rice (Oryza sativa L.) seedlings with root surface iron plaque

Rice seedlings were grown in hydroponic culture to determine the effects of external Zn and P supply on plant uptake of Cd in the presence or absence of iron plaque on the root surfaces. Iron plaque was induced by supplying 50 mg l⁻¹ Fe²⁺ in the nutrient solution for 2 day. Then 43-day-old seedlings were exposed to 10 μmol l⁻¹ Cd together with 10 μmol l⁻¹ Zn or without Zn (Zn–Cd experiment), or to 10 μmol l⁻¹ Cd with 1.0 mmol l⁻¹ P or without P (P–Cd experiment) for another 2 day. The seedlings were then harvested and the concentrations of Fe, Zn, P and Cd in dithionite–citrate–bicarbonate (DCB) extracts and in roots and shoots were determined. The dry weights of roots and shoots of seedlings treated with 50 mg l⁻¹ Fe were significantly lower than when no Fe was supplied. Adsorption of Cd, Zn and P on the iron plaque increased when Fe was supplied but Cd concentrations in DCB extracts were unaffected by external Zn or P supply levels. Cd concentrations in shoots and roots were lower when Fe was supplied. Zn additions decreased Cd concentrations in roots but increased Cd concentrations in shoots, whereas P additions significantly increased shoot and root Cd concentrations and this effect diminished when Fe was supplied. The percentage of Cd in DCB extracts was significantly lower than in roots or shoots, accounting for up to 1.8–3.8% of the plant total Cd, while root and shoot Cd were within the ranges 57–76% and 21–40% respectively in the two experiments. Thus, the main barrier to Cd uptake seemed to be the root tissue and the contribution of iron plaque on root surfaces to plant Cd uptake was minor. The changes in plant Cd uptake were not due to Zn or P additions altering Cd adsorption on iron plaque, but more likely because Zn or P interfered with Cd uptake by the roots and translocation to the shoots.     

Effects of silicon oxide nanoparticles on growth and physiology of wheat seedlings

The effects of silicon oxide (SiO₂) nanoparticles at concentrations of 50, 100, 200, 400, and 800 mg/L on Triticum aestivum L. seedlings were investigated. We showed that SiO₂ nanoparticles, at concentrations higher 200 mg/L, had negative impacts on wheat seedlings. At these concentrations, SiO₂ nanoparticles significantly decreased roots and shoots fresh weight, decreased roots and shoots dry weight, decreased amounts of chlorophyll a and b in leaves, decreased amount of carotenoids in leaves, increased proline content in leaves, increased lipid peroxidation in leaves, and increased catalase activity in leaves. Results of this study indicate that at lower concentrations (such as 50 and 100 mg/L), SiO₂ nanoparticles not only have negative effects on wheat seedlings, but can have even some positive effects.     

Root exudation and Fe uptake and transport in wheat genotypes differing in tolerance to Zn deficiency

Tolerance to Zn deficiency in wheat germplasm may be inversely related to uptake and transport of Fe to shoots. The present study examined eight bread (Triticum aestivum) and two durum (T. turgidum L. conv. durum) wheat genotypes for their capacity to take up and transport Fe when grown under either Fe or Zn deficiency. Bread wheat genotypes Aroona, Excalibur and Stilleto showed tolerance to Zn and Fe deficiency, while durum wheat genotypes are clearly less tolerant to either deficiency. Roots of bread wheats tolerant to Zn deficiency exuded more phytosiderophores than sensitive bread and durum genotypes. Greater amounts of phytosideophores were exuded by roots grown under Fe than Zn deficiency. A relatively poor relationship existed between phytosiderophore exudation or the Fe uptake rate and relative shoot growth under Fe deficiency. At advanced stages of Zn deficiency, genotypes tolerant to Zn deficiency (Aroona and Stilleto) had a greater rate of Fe uptake than other genotypes. Zinc deficiency depressed the rate of Fe transport to shoots in all genotypes in early stages, while advanced Zn deficiency had the opposite effect. Compared with Zn-sufficient plants, 17-day-old Zn-deficient plants of genotypes tolerant to Zn deficiency had a lower rate of Fe transport to shoots, while genotypes sensitive to Zn deficiency (Durati, Yallaroi) had the Fe transport rate increased by Zn deficiency. A proportion of total amount of Fe taken up that was transported to shoots increased with duration of either Fe or Zn deficiency. It is concluded that greater tolerance to Zn deficiency among wheat genotypes is associated with the increased exudation of phytosiderophores, an increased Fe uptake rate and decreased transport of Fe to shoots. This revised version was published online in June 2006 with corrections to the Cover Date.     

Influence of lanthanum on the uptake of trace elements in cucumber plant

The effects of La³⁺ on the uptake of trace elements (Se, Co, V, and Tc) in cucumber plants were studied by a radioactive multitracer technique. It was observed that the uptake and distribution of these trace elements in roots, stems, and leaves are different under different La³⁺ treatments. Furthermore, in the control, the plant accumulates ⁷⁵Se, ⁵⁶Co, and ⁴⁸V all in the order roots>leaves>stems, whereas ^95mTc was in the order leaves>stems>roots. The accumulations of ⁷⁵Se and ^95mTc in plants treated with different La³⁺ concentration were in the same order as those in the control, but the uptakes percentages of other kinds of element changed differently. The results indicate that lanthanum treatments to a growing cucumber lead to the change of uptake of trace elements, which suggest that a rare earth element is directly or indirectly involved in the ion transport of the plant and affects plant growth by regulating the uptake and distribution of elements that influence the plant cell physiology and biochemistry.     

Counteraction of Salinity Stress on Wheat Plants by Grain Soaking in Ascorbic Acid, Thiamin or Sodium Salicylate

The interactive effects of salinity stress (40, 80, 120 and 160 mM NaCl) and ascorbic acid (0.6 mM), thiamin (0.3 mM) or sodium salicylate (0.6 mM) were studied in wheat (Triticum aestivum L.). The contents of cellulose, lignin of either shoots or roots, pectin of root and soluble sugars of shoots were lowered with the rise of NaCl concentration. On the other hand, the contents of hemicellulose and soluble sugars of roots, starch and soluble proteins of shoots, proline of either shoots or roots, and amino acids of roots were raised. Also, increasing NaCl concentration in the culture media increased Na⁺ and Ca²⁺ accumulation and gradually lowered K⁺ and Mg²⁺ concentration in different organs of wheat plant. Grain soaking in ascorbic acid, thiamin or sodium salicylate could counteract the adverse effects of NaCl salinity on the seedlings of wheat plant by suppression of salt stress induced accumulation of proline.