H2 15O translocation in rice was enhanced by 10 μm 5-aminolevulinic acid as monitored by positron emitting tracer imaging system (PETIS)

5-Aminolevulinic acid (ALA) acts to increase chlorophyll biosynthesis, photosynthesis, cold stress tolerance, and salt tolerance at low concentrations. We studied the effects of ALA on H₂ ¹⁵O translocation from the roots to the shoots of rice plants (Oryza sativa L. cv. Nipponbare) in real time by a positron-emitting tracer imaging system (PETIS). When the plant was treated with 10 μm ALA, the velocity of the H₂ ¹⁵O translocation from 2 to 12 min after absorption increased to 126, 137, 140% that of the control at 1.5, 2.5, and 3.5 h after ALA treatment, respectively. However, ALA did not affect the H₂ ¹⁵O translocation within 0.5 h of treatment. When the plant was treated with 0.1 mM ABA at 4 h after 10 μm ALA treatment, the velocity of the H₂ ¹⁵O translocation decreased at 0.5 h after ABA treatment. Those observations suggested ALA might be absorbed and transported to the guard cells within 1.5 h and functioned to expand the stomatal aperture.     

Visualization of 15O-water flow in tomato and rice in the light and dark using a positron-emitting tracer imaging system (PETIS)

Abstract

¹⁵P-water flow from the roots to the top in tomato (Lycopersicon esculentum Mill.) and rice (Oryza sativa L.) plants was visualized with time using a positron-emitting tracer imaging system (PETIS). The ¹⁵O-water flow was switched on by light and completely stopped in the dark. The flow rate in the stem of tomato and the shoot of rice at a light intensity of 500 μmol·m^?2·s^?1 was 1.9 and 0.4 cm min^?1, respectively.     

Alleviation of Manganese Phytotoxicity in Barley with Calcium

In order to clarify the mechanism by which calcium (Ca) alleviates manganese (Mn) phytotoxicity, barley plants were grown under the following conditions: (1) nutrient solution alone (control), (2) nutrient solution + 25 μM Mn (Mn-toxic), and (3) nutrient solution + 25 μ M Mn + 20 mM Ca (Ca-alleviated). Feeding experiments using ⁵⁴Mn and ⁵⁹Fe (iron) with 2.0 or 20 mM Ca to the plant roots were also conducted. The absorption and translocation of ⁵⁴Mn in the control plants were lowered by the high-Ca (20 mM) feeding condition. The translocation of ⁵⁴Mn to shoots of Mn-toxic or Ca-alleviated plants was also lowered by the high-Ca feeding condition, but ⁵⁴Mn absorption by roots of the plants was unaffected. The absorption and translocation of ⁵⁹Fe in the plants was unaffected by the high-Ca feeding condition. Calcium alleviation of Mn phytotoxicity in barley may be induced mainly by the inhibition of Mn translocation to shoots.     

Gornig,Cleve A.I. und Hanaker,J.W. (Hrsg.): Organic Chemicals in the soil environment Vol. I u. II. zus. 968 S., Preis 24,50 und 26,50 US $. Verlag Marcel Dekker,New York 1972

Investigations on translocation of magnesium (²⁸Mg) in sunflower plants. 1. The translocation and retranslocation of Mg respectively ²⁸Mg in sunflower plants of different age have been investigated. The focus of this investigation was on the influence of the composition of the uptake solution and the age of plants on the uptake of Mg respectively ²⁸Mg through the roots or through the leaves and on Mg translocation (distribution). 2. After sunflower plants were grown in Mg-deficient 1/2-Hoagland solution Mg in the plants were redistributed. The Mg in the roots, stems, cotyledons, primary and secondary leaves was retranslocated to the youngest leaves. 3. In isolated, secondary-rooted sunflower shoots grown in Mg-deficient solution, plant Mg was retranslocated into the new roots and into the youngest shoots. 4. The ²⁸Mg-uptake from the 0,2 mM MgSO₄ solution was usually higher than from the 1/10-Hoagland solution. The composition of the uptake solution had little influence on the distribution of ²⁸Mg. Independent of the age plants had the highest ²⁸Mg content in the young and the lowest in the old leaves. 5. Root uptake of ²⁸Mg resulted in a more uniform distribution in the plant than leaf uptake. The old leaves had a higher ²⁸Mg content by root uptake than by leaf uptake of ²⁸Mg. This is probably influenced by transpiration, in combination with the xylem transport of ²⁸Mg after root uptake, which differs from leaf uptake and translocation in basipetal direction. 6. With increased age of plants, the content of ²⁸Mg/10 gr. fresh weight decreased and the difference in content between the parts of plant was higher. The decrease of Mg content in the oldest leaves was the highest. 7. The results showed that Mg was transportable in the phloem. The magnitude and the direction of Mg transport was determined as primarily through the assimilation stream, which is coupled with Mg transport in plants.     

Real-time imaging of nitrogen fixation in an intact soybean plant with nodules using 13N-labeled nitrogen gas

Abstract

Real-time images of nitrogen fixation in an intact nodule of hydroponically cultured soybean (Glycine max [L] Merr.) were obtained. In the present study, we developed a rapid method to produce and purify ¹³N-labeled radioactive nitrogen gas (half life: 9.97?min). ¹³N was produced from a ¹⁶O (p, α) ¹³N nuclear reaction. The target chamber was filled with CO₂ and irradiated for 10?min with protons at an energy of 18.3?MeV and an electric current of 5?μA, which was delivered from a cyclotron. All CO₂ in the collected gas was absorbed and removed with powdered soda-lime in a syringe and replaced with helium gas. The resulting gas was injected into gas chromatography and separated and a 35?mL fraction, including the peak of [¹³N]-nitrogen gas, was collected by monitoring the chromatogram. The obtained gas was mixed with 10?mL of O₂ and 5?mL of N₂ and used in the tracer experiment. The tracer gas was fed into the underground part of intact nodulated soybean plants and serial images of the distribution of ¹³N were obtained non-invasively using a positron-emitting tracer imaging system (PETIS). The rates of nitrogen fixation of the six test plants were estimated to be 0.17?±?0.10?μmol N₂?h^?1 from the PETIS image data. The decreasing rates of assimilated nitrogen were also estimated to be 0.012?±?0.011?μmol?N₂?h^?1. In conclusion, we successfully observed nitrogen fixation in soybean plants with nodules non-invasively and quantitatively using [¹³N]N₂ and PETIS.     

Effect of Free Manganese Activity on Yield and Uptake of Micronutrient Cations by Barley and Oat grown in Chelator-buffered Nutrient Solution

The uptake of micronutrient cations in relation to varying activities of Mn²⁺ was studied for barley (Hordeum vulgare L. var. Thule) and oat (Avena sativa L. var. Biri) grown in chelator buffered nutrient solution. Free activities of Mn²⁺ were calculated by using the chemical speciation programme GEOCHEM-PC. Manganese deficient conditions induced elevated concentrations of Zn and Fe in shoots of both species. The corresponding antagonistic relationship between Mn and Cu could only be seen in barley. The observed antagonistic relationships were only valid as long as the plant growth was limited by Mn deficiency. The Mn concentration in both plant species increased significantly with increasing Mn²⁺ activity in the nutrient solution. The concentration of Mn in the shoots of oat was higher than for barley except under severe Mn deficiency where it was found equal for both species. Manganese was accumulated in the roots of barley at high Mn²⁺ activity. The different shoot concentrations of Mn between barley and oat are therefore attributed to the extent of Mn translocation from roots to shoots. Manganese deficiency induced a significant increase in the shoot to root ratio in both species.     

Effect of supplied phytosiderophore on 59Fe absorption and translocation in Fe-deficient barley grown hydroponically in low phosphorus media

Abstract

Hydroponically grown barley plants (Hordeum vulgare L. cv. Minorimugi) under iron-deficient (–Fe) and high phosphorus (P) conditions (500 µmol L^?1) showed Fe chlorosis and lower growth compared with plants grown in –Fe and low P conditions (50, 5 and 0.5 µmol L^?1). To understand the physiological role of P in regulating the growth of plants in –Fe medium, we carried out an Fe feeding experiment using four P levels (500, 50, 5 and 0.5 µmol L^?1) and phytosiderophores (PS), mugineic acid. Our results suggest that plants grown in a high P medium had higher absorption activity of ⁵⁹Fe compared with plants grown in low P media, irrespective of the presence or absence of added PS. Translocation of ⁵⁹Fe from roots to shoots was not affected by the P level. The relative translocation rate of ⁵⁹Fe increased with decreasing levels of P in the medium. In general, the addition of PS enhanced the absorption of ⁵⁹Fe and its translocation. Taken together these results suggest that the lower relative translocation rate of Fe in high P plants may be induced by the physiological inactivation of Fe in the roots, and the higher absorption activity of Fe in high P conditions possibly results from the response of barley plants to Fe deficiency.     

Die Wirkung der Schwermetalle Chrom,Nickel, Kupfer,Zink, Cadmium,Quecksilber und Blei auf die Aufnahme und Verlagerung von Kalium und Phosphat bei jungen Gerstenpflanzen

Effect of the heavy metals chromium, nickel, copper, zinc, cadmium, mercury and lead on uptake and translocation of K and P by young barley plants The uptake of potassium and phosphate into the roots and shoots of 7 days old barley plants from double-labelled (⁴²K, ³²P) nutrient solutions containing chromium, nickel, copper, zinc, cadmium, mercury or lead (10^?6 - 10^?4 moles/1) was measured in a constant environment after 5 hours, in order to compare early stages of toxicity. K and P uptake and translocation were inhibited by the 7 heavy metals to a different extent; K was more affected than P, and translocation of both nutrients into the shoots was more inhibited than uptake into the roots. Plants showed no visible injuries. Mercury had by far the greatest effect, zinc was almost ineffective: K uptake e.g. was reduced to 21% of the control by 10^?4 moles Hg/l, but only to 97% by the same amount of Zn, and P translocation was reduced to 8% by Hg, but was not affected by Zn. The least significant effect of Hg was detectable at a concentration of 4.10^?7 moles Hg/l ( = 0,08 ppm) in the nutrient solution, the effect of Zn only above 10^?4 moles Zn/l ( = 6,5 ppm). Arranging the tested heavy metals according to their effects leads to the sequence Hg > Pb > Cu > Cd > Cr > Ni > Zn which corresponds – apart from two deviations – to the electrochemical series of the elements.     

Performance of Sorghum Grown on a Salt Affected Soil Manured with Dhaincha Plant Residues Using a 15N Isotopic Dilution Technique

A field experiment was conducted on a salt-affected soil to determine the effect of application of three types of Dhaincha (Sesbania aculeata Pers.) residues (R, roots; L, shoots; L+R, shoots plus roots) on the performance of sorghum (Sorghum bicolor L.) using the indirect ¹⁵N isotopic dilution technique. Results indicated that sesbania residues (L and L+R), used as green manures, significantly increased grain yield, dry matter production, N uptake, and water use efficiency of sorghum. Percentages of nitrogen (N) derived from residues (%Ndfr) in sorghum ranged from 6.4% to 28%. The N recoveries in sorghum were 52%, 19.6% and 19.7% of the total amount contained in sesbania roots, shoots and roots plus shoots, respectively. The beneficial effects of sesbania residues are attributed not only to the additional N availability to the plants, but also to effects on the enhancement of soil N uptake, particularly in the L+R treatment. The findings suggest that the use of Sesbania aculeata residues, as a green manure, can provide a substantial portion of total N in sorghum. In addition, the use of sesbania green manure in salt-affected soils, as a bio-reclaiming material, can be a promising approach for enhancing plant growth on a sustainable basis.     

Effects of Manganese on Uptake and Translocation of Nutrients in a Hyperaccumulator

The effects of manganese (Mn) on the growth and Mn-induced changes in nutrients uptake and translocation in Mn hyperaccumulator Phytolacca acinosa was investigated in this study. Results showed that high Mn (5000 μ M) in culture solution lead to typical Mn toxicity symptoms in leaves of P. acinosa and decrease of dry matter accumulation in shoots whereas there are no obvious toxicity symptoms and significant decrease of dry weight in roots. Manganese accumulation in roots, stems, and leaves increased with the increment of Mn concentration at the medium level. Calcium (Ca), magnesium (Mg), and iron (Fe) concentration in organs of P. acinosa decreased as the Mn concentration in the nutrient solution increased, but the Ca and Mg concentrations were still at a normal level and the Fe concentration at a sufficient level when compared with the normal plants. The Zn concentration affected by higher Mn level occurred only in roots of P. acinosa and the P concentration affected only in stems, whereas there were no significant influences of excess Mn on the potassium (K) and copper (Cu) concentration in organs of P. acinosa.     

Uptake and translocation of nitrogen in patumma (Curcuma alismatifolia) by leaves or root

An adequate supply of nitrogen (N) is important for patumma growth and flower quality. This study aimed to compare the uptake and translocation of N by foliar and root application. Fertilization with ¹⁵ nitrate (NO₃)-N via roots or leaves was carried out at four stages, at the 1st to 4th fully expanded leaf (FEL) stages, and the plants were sampled at each successive stage. The uptake and translocation of ¹⁵N from foliar or root applications showed relatively similar patterns at all stages. Although the N fertilizer utilization rate by roots was higher than that via leaves, the foliar application stimulated reproductive growth by earlier flowering. The N supplied at the 1st FEL and the 2nd FEL was utilized mainly in leaves, whereas supplying N at the 3rd and 4th FEL promoted flower quality. Fertilizer application method and stage of application influence the utilization rate and translocation of N to the sink organs.     

Physiological and Mineralogical Properties of Arsenic-Induced Chlorosis in Barley Seedlings Grown Hydroponically

The experiment was carried out to investigate the effects of arsenic (As) on the physiological and mineralogical properties of barley (Hordeum vulgare L. cv. ‘Minorimugi’). The plants were grown in nutrient solution treated with 0, 6.7, 33.5, and 67 μ M As (0, 0.5, 2.5, and 5 ppm As, respectively) in the phytotron. Dry matter yield of shoots and roots decreased significantly with the As treatments, indicating that barley plants are As-sensitive and As-toxicity depends on the As concentration in the rooting medium. Necrosis in older leaves and chlorosis symptoms (whitish color) in the fully developed young leaves were observed at the 33.5 and 67 μ M As treatments. Arsenic concentration, accumulation, and translocation increased with the increase of As concentration in the rooting medium. Arsenic was mostly concentrated in roots and a little amount was moved to shoots, indicating that As was not easily translocated to shoots of barley seedlings. Concentrations and accumulations of phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), manganese (Mn), zinc (Zn), and copper (Cu) decreased significantly in shoots for 33.5 and 67 μ M As treatments as compared to the 0 μ M As treatment. Concentrations of P, K, Ca, Mg, Mn, and Cu decreased in roots, but Zn concentration increased in roots at 67 μ M As treatment. Accumulations of P, K, Ca, Mg, Mn, Zn, and Cu in roots also decreased significantly at 67 μ M As treatment. Accumulation of P and the cations showed negative relationship with As. Concentration of Fe decreased in shoots at 33.5 and 67 μ M As treatments where chlorosis was induced in the young leaf but increased in roots at 33.5 and 67 μ M As treatments. It was suggested that As might induce iron (Fe)-chlorosis in the plants. Among the micronutrients, Fe translocation was more affected than others by As. Phytosiderophore (PS) accumulation in roots, which is a symptom of Fe-deficiency in grasses, did not change significantly between 0 and 33.5 μ M As treatments; indicating that As-induced chlorosis did not enhance PS accumulation in roots and decreased due to As-toxicity at 67 μ M As treatment.     

Influence of Mercury on Soybean Plants (Glycine max L.) at Low pH

The influence of Hg on soybean plants under different pH conditions and Hg concentrations was studied. Growth inhibition by Hg was higher in roots than the upper part of the plant, but was highly dependant on pH condition. Growth inhibition of roots was observed when Hg concentration was higher than 1 mg Hg L^?1 for pH 4.0 and 5 mg Hg L^?1 for pH 6.0. Using ²⁰³Hg as a radioactive tracer, the amount of Hg (1 mg Hg L^?1) uptake in root was found to be about 1.5 times higher at pH 4.0 than that at pH 6.0; suggesting that Hg when highly accumulated at the lower pH induced inhibition of root growth. Decreased amounts of Hg due to evaporation during the plant growth were very low, but were higher at pH 6.0 than that at pH 4.0. There was hardly any translocation of Hg from roots to the upper parts through the stem within 24 h.     

Effect of cadmium toxicity on micronutrient concentration,uptake and partitioning in seven rice cultivars

Heavy metal uptake, translocation and partitioning differ greatly among plant cultivars and plant parts. A pot experiment was conducted to determine the effect of cadmium (Cd) levels (0, 45 and 90 mg kg^?1 soil) on dry matter yield, and concentration, uptake and translocation of Cd, Fe, Zn, Mn and Cu in seven rice cultivars. Application of 45 mg Cd kg^?1 soil decreased root and shoot dry weight. On average, shoot and root Cd concentrations and uptake increased in all cultivars, but micronutrients uptake decreased following the application of 45 mg Cd kg^?1. No significant differences were observed between 45 and 90 mg kg^?1 Cd levels. On average, Cd treatments resulted in a decrease in Zn, Fe and Mn concentrations in shoots and Zn, Cu and Mn concentrations in roots. Differences were observed in Cd and micronutrient concentrations and uptake among rice cultivars. Translocation factor, defined as the shoot/root concentration ratio indicated that Cu and Fe contents in roots were higher than in shoots. The Mn concentration was much higher in shoots. Zinc concentrations were almost similar in the two organs of rice at 0 and 45 mg Cd kg^?1. A higher Cd level, however, led to a decrease in the Zn concentration in shoots.     

Elevated CO2 concentrations increase leaf nitrate reduction by strengthening sink activity in soybean plants

An experiment was conducted to examine the effect of CO₂ enrichment on the nitrate uptake, nitrate reduction activity, and translocation of assimilated-N from leaves at varying levels of nitrogen nutrition in soybean using ¹⁵N tracer technique. CO₂ enrichment significantly increased the plant biomass, apparent leaf photosynthesis, sugar and starch contents of leaves, and reduced-N contents of the plant organs only when the plants were grown at high levels of nitrogen. A high supply of nitrogen enhanced plant growth and increased the reduced-N content of the plant organs, but its effect on the carbohydrate contents and photosynthetic rate were not significant. However, the combination of high CO₂ and high nitrogen levels led to an additive effect on all these parameters. The nitrate reductase activity increased temporarily for a short period of time by CO₂ enrichment and high nitrogen levels. ¹⁵N tracer studies indicated that the increase in the amount of reduced-N by CO₂ enrichment was derived from nitrate-N and not from fixed-N of the plant. To examine the translocation of reduced-N from the leaf in more detail, another experiment was conducted by feeding the plants with ¹⁵NO₃-N through a terminal leaflet of an upper trifoliated leaf under depodding and/or CO₂ enrichment conditions. The export rate of ¹⁵N from the terminal leaflet to other plant parts decreased by depodding, but it increased by CO₂ enrichment. CO₂ enrichment increased the percentage of plant ¹⁵N in the stem and / or pods. Depodding increased the percentage of plant ¹⁵N in the leaf and stem. The results suggested that the increase in the leaf nitrate reduction activity by CO₂ enrichment was due to the increase of the translocation of reduced-N from leaves through the strengthening of the sink activity of pods and / or stem for reduced-N.     

Root responses of sterile‐grown onion plants to iron deficiency 1

Onion (Allium sativum) plants grown without iron (Fe) in sterile nutrient solutions readily developed chlorosis symptoms. Iron deficiency in the sterile‐grown plants stimulated the rates of root extracellular reduction of Fe³⁺, copper (Cu²⁺), manganese (Mn⁴⁺), and other artificial electron acceptors. While rapid reduction occurred with the synthetic chelate Fe³⁺HEDTA, no short‐term reduction occurred with the fungal siderophore Fe³⁺ferrioxamine B (FeFOB). In addition to the increased rate of extracellular electron transfer at the root surfaces, the Fe‐deficient plants showed greater rates of Fe uptake and translocation than the onion plants grown with Fe. The rates of uptake and translocation of Fe were sharply higher for the Fe‐deficient plants supplied with FeHEDTA than for similar plants supplied with FeFOB. Inhibition by BPDS of the Fe uptake by the Fe‐deficient onion plants further supported the importance of Fe³⁺ chelate reduction for the uptake of Fe into the roots. Rates of Fe uptake and translocation by Fe‐deficient onion plants supplied with ⁵⁵FeFOB were identical to the rates of uptake of ferrated [14C]‐FOD; a result that gives evidence of the uptake and translocation of the intact ferrated siderophore, presumably by a mechanism not involving prior extracellular Fe³⁺ reduction. Differences in the rates of transport of other micronutrients into the roots of the Fe‐deficient onion plants were evident by the significantly higher Zn and Mn levels in the shoots of the Fe‐deficient onion.     

The difference in N metabolism between NAD(P)H-specific NR-deficient mutant and wild-type barley (Hordeum vulgare L.)

Abstract

Barley (Hordeum vulgare L.) is an important crop for cereal research. In this study, two barley genotypes the wild-type (Steptoe) and the mutant (Az12) were used. An experiment was conducted using ¹⁵N-tracing method to NADH-specific nitrate reductase (NR)-deficient mutant seedling of barley. The N-depleted seedlings were exposed to a nutrient solution containing nitrate and nitrite, and were labeled with ¹⁵N for 38?h under (14?L/10D) cycles. The two genotypes utilized ¹⁵NO₃^? and accumulated it as reduced ¹⁵N, predominately in the shoots. However, nitrate reduction in the Az12 shoots was 9% lower than that in the Steptoe shoots at 38?h. As a result, in the Az12, nitrate accumulation in shoots was 78% higher than that in the Steptoe. Accumulation of reduced ¹⁵N in the Az12 roots was nearly similar to that of the Steptoe roots, but 8% lower in the Az12 shoots than in the Steptoe shoots at the end of the experiment. Also for both genotypes, root contribution increased during L/D cycles and decreased during the subsequent light cycle. Upward transport of reduced ¹⁵N via the xylem in the Az12 was nearly two times higher than that in Steptoe during the second light period (24–38?h). In both genotypes, xylem transport of reduced ¹⁵N was far exceeded the downward phloem transport. Abbreviations Anl accumulation of reduced ¹⁵N from ¹⁵NO₃^? in non-labeled roots of split roots

Ar accumulation in roots of reduced ¹⁵N from ¹⁵NO₃^?

As accumulation in shoots of reduced ¹⁵N from ¹⁵NO₃^?

Rr ¹⁵NO₃^? reduction in roots

Rs ¹⁵NO₃^? reduction in shoots

Tp translocation to root of shoot reduced ¹⁵N from ¹⁵NO₃^? in phloem

Tx translocation to shoot of root-reduced ¹⁵N from ¹⁵NO₃^? in xylem

FW fresh weight

     

Effects of Nickel on Growth and Composition of Metal Micronutrients in Barley Plants Grown in Nutrient Solution

Abstract

A hydroponic experiment was conducted in a phytotron at pH 5.5 to study the effects of nickel (Ni) on the growth and composition of metal micronutrients, such as copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn), of barley (Hordeum vulgare L. cv. Minorimugi). Four Ni treatments were conducted (0, 1.0, 10, and 100 μM) for 14 d. Plants grown in 100 μM Ni showed typical visual symptoms of Ni toxicity such as chlorosis, necrosis of leaves, and browning of the root system, while other plants were free from any symptoms. Dry weights were the highest in plants grown in 1.0 μM Ni, with a corresponding increase in the chlorophyll index of the plants, suggesting that 1.0～10 μM Ni needs to be added to the nutrient solution for optimum growth of barley plants. The increase of Ni in the nutrient solutions increased the concentrations of Cu and Fe in roots, while a decrease was observed in shoots. The concentrations of Mn and Zn in shoots and roots of plants decreased with increasing Ni supply in the nutrient solution. Shoot concentrations of Cu, Fe, Mn, and Zn in plants grown at 100 μ M Ni were below the critical levels for deficiency. Plants grown at 1.0 μ M Ni accumulated higher amounts of Cu, Fe, Mn and Zn, indicating that nutrient accumulation in plants was more influenced by dry weights than by nutrient concentrations. The translocation of Cu and Fe from roots to shoots was repressed, while that of Mn and Zn was not repressed with increasing Ni concentration in the nutrient solution.     

Effect of Salt Stress and Manganese Supply on Growth of Barley Seedlings

Abstract

Effect of supplemental manganese (Mn) on the growth of salt-stressed barley (Hordeum vulgare L.) was assessed to determine if a salinity-induced Mn deficiency was limiting plant growth. Sodium chloride (NaCl) was added to the black-cotton soil and salinity was maintained at 0.3, 4, 8, 12, and 16 dS m^?1. A negative relationship between percent seed germination and increasing salt concentration was obtained, however, results suggested that barley is salt tolerant at seed germination stage. Increasing concentration of NaCl significantly reduced plant growth. Also, salinity induced a Mn deficiency in shoots of plants. Manganese was added to the soil at control and at 8 dS m^?1 salinity. Supplemental Mn improved the growth of salt-stressed plants to a limited extent, but it did not improve the growth of control plants. Further, supplemental Mn increased the relative growth rate of salt-stressed plants and this increase was attributed to an increase in the net assimilation rate of salt-stressed plants and not to leaf area ratio. Salt concentration adversely affected the uptake of nitrogen and phosphorus by plants, which resulted in imbalance of nutrients in salt-stressed plants. It appears that factors other than Mn, such as ionic, water- and nutrient-stresses can limit the growth of salt-stressed plants and supplemental Mn has only a limited role in mitigation of adverse effect of salinity.     

Effect of chelating agents on phytotoxicity of lead and lead transport

Abstract

The major purpose of these experiments was to determine if Pb uptake by plants was significantly increased by chelating agents used in plant nutrition. The interaction of Pb with some other elements in barley plants (Hordeum vulgare L. C.V. Atlas 57) and bush bean (Phaseolus vulgaris L. C.V. Improved Tendergreen) was studied in a glasshouse with different rates of Pb in solution culture and in amended (control, S, CaCO₃, MgCO₃) Yolo loam soil with and without the chelating agent DTPA (diethylene triamine pentaacetic acid). In a solution culture experiment, 10^‐3 M Pb significantly decreased bush bean yields in both control and DTPA treatments. The CaCO₃ added to nutrient solution decreased the concentration of Pb in leaves, stems, and roots and prevented the toxicity of 10^‐3 M Pb⁺⁺. At high Pb levels, interactions between Pb and Mn and Pb and Fe were observed, except with CaCO₃. In the soil experiment, the yields of barley and bush bean were influenced only slightly by Pb. The Pb concentration in barley shoots and bush bean leaves and stems was increased considerably in the presence of DTPA, however. In the absence of DTPA, the effect of added Pb was very small in the control and S amended soil treatments and almost negligible in the CaCO₃ and MgCO₃ amended soil treatments. Application of DTPA facilitated the translocation of Pb, Fe, Mn, Cu, and Zn to shoots. The effect was dependent upon soil pH. Particularly, the Fe was increased by DTPA at low pH while the effect was negligible at high pH. This was opposite the effect on Pb. The DTPA resulted in considerable Pb transport to leaves and stems at high soil pH. The uptake pattern of Zn and Cu was similar to that of Pb. It can be expected that chelating agents can increase the migration of Pb to plants andincrease its uptake by plants, and hence, entry into food chains.