Impact of molybdenum on Chinese cabbage response to selenium in solution culture

Molybdenum (Mo) and selenium (Se) are both essential micronutrients for animals and humans. Increasing Mo and Se contents in food crops offers an effective approach to reduce Mo and Se deficiency problems. A hydroponic trial was conducted to investigate the interactions of Mo and Se on uptake, transfer factors (TF _shoot ) as well as distribution coefficients (DC) of Mo and Se on Chinese cabbage (Brassica campestris L. ssp. Pekinensis). In Experiment 1 three concentrations of Mo (0.01, 0.1 and 1?mg?L^?1) and four concentrations of Se (0, 0.01, 0.1 and 1?mg?L^?1) were arranged with a randomized block design. In Experiment 2, there were three treatments, 0.1?mg?L^?1 Mo, 0.1?mg?L^?1 Se and a combination of 0.1?mg?L^?1 Mo?+?0.1?mg?L^?1 Se. Experiment 1 showed that Se decreased Mo concentrations in shoots and roots. The impact of Mo on Chinese cabbage response to uptake of Se varied, depending on whether the root Se concentration was saturated or not; Experiment 2 showed that there is a strong antagonism between Mo and Se on nutrition uptake when Mo and Se deficiencies persist for long periods; Mo and Se were easily translocated from solution to plants and from roots to shoots. The results will also be of help in cultivating Mo-enriched and Se-enriched crops.     

MODULATION OF MACRONUTRIENTS UPTAKE AND TRANSLOCATION IN Mn-TREATED RICE IN EARLY STAGES OF VEGETATIVE GROWTH

The effect of increasing manganese (Mn) concentrations on calcium (Ca), potassium (K), magnesium (Mg), sodium (Na), and phosphorus (P) absorption and translocation was studied in rice (Oryza sativa L. cv. Safari), before and after the end of mobilization of seed reserves. Rice plants were grown over a 15-, 21-, and 28-day period in nutrient solutions containing Mn concentrations varying between 0.125 and 32 mg L^?1. It was found that increasing Mn concentrations in the nutrient solution was coupled to an increasing net uptake, total shoot accumulation, and root and shoot contents of this metal during all the experimental periods. Concerning the translocation rates, in 15-day-old plants a decrease was found after the 2 mg L^?1 Mn treatment, but from the 21st day onward an increase was found until the highest treatment. The modulating action of Mn in macronutrient accumulation displayed different patterns among the experimental periods. In the root tissues of 15-day-old plants, Ca decreased significantly until the 2 mg L^?1 treatment and Na increased. In the shoots, the contents of P and Na decreased, but K and Mg showed significant increases. Until the 32 mg L^?1 Mn treatment, the ratio between root and shoot concentrations of K and Mg decreased in these plants. A similar pattern was also found for Ca until the 2 mg L^?1 Mn treatment. That ratio increased for Na. Plant total amount of Ca sharply decreased. Shoot total amount of Na and P also decreased, but the pattern of Ca increased until the 2 mg L^?1 Mn treatment. The concentrations of K increased in the root tissues 21 days after germination, but the levels of Ca, Mg, Na, and P decreased. In the shoots, the concentrations of Ca and Mg decreased significantly. Until the 32 mg L^?1 Mn treatment, the ratio between root and shoot concentration of Na and P increased, whereas those of Ca and Mg decreased. An increase was found for the plant and shoot total amount of Ca, K, and Mg until the last Mn treatment, but an opposite trend was found for Na and P. Additionally, until the 32 mg L^?1 Mn treatment, an increase was found for the proportions of Ca and Mg translocated to the shoot, but an opposite trend was detected for P. It was concluded that before and after the end of the mobilization of seed reserves, the net uptake rate of Ca is reversed, and, moreover, a similar trend is shown for the net translocation of Mg. A major implication of this process is the alteration of the related pattern for shoot accumulation. Eventually a different selectivity of the K⁺:Na⁺ ratio is also developed in the roots.     

Interactive Effects of Lanthanum and Cadmium on Plant Growth and Mineral Element Uptake in Crisped-Leaf Mustard Under Hydroponic Conditions

Plant growth and mineral element accumulation in Brassica juncea var. crispifolia (crisped-leaf mustard) under exposure to lanthanum (La) and cadmium (Cd) were studied by employing a hydroponic experiment with a complete two-factorial design. Four levels of La (0.05–5.0 mg L^?1) and two levels of Cd (1.0 and 10.0 mg L^?1) were used in this experiment. Lanthanum did not improve plant growth in this experiment. Addition of La (≥ 1.0 mg L^?1) or Cd (≥ 10 mg L^?1) to the solution inhibited root elongation. Lanthanum treatments reduced accumulations of iron (Fe), manganese (Mn), and zinc (Zn) in roots, and Mn in shoots. Lanthanum at ≥ 1.0 mg L^?1 limited the Cd translocation from roots to shoots and thus decreased the accumulation of Cd in shoots. Cadmium had no influence on La accumulations in roots, but inhibited the accumulation of La in shoots. The study results suggest that applications of rare earth elements in vegetables would be potentially risky to human health.     

MOLYBDENUM STRESS AFFECTS VIABILITY AND VIGOR OF WHEAT SEEDS

Wheat (Triticum aestivum L.) cv. Sonalika was grown in refined sand at variable molybdenum (Mo) supply ranging from acute deficiency (0.00002 mg L^?1) to excess (10 mg L^?1). Deficiency as well as excess of Mo decreased significantly the biomass, grain yield, Mo content in leaves and seeds and activity of nitrate reductase in leaves. The effect of high (>0.02 mg L^?1) Mo was more marked than its deficiency on wheat. Low and excess Mo deteriorated the quality of grains by lowering the content of starch, sugars, protein, non-protein, and total nitrogen (N) as well as that of prolamin, glutelin, and globulin fractions of seed proteins and increasing the content of albumin and electrical conductivity (EC) of seed leachate. Molybdenum deficiency and excess both resulted in production of lightweight immature seeds, poor in vigor and germination potential. The post fertilization developmental stages required one tenth of the adequate Mo supply for normal bold seed production in wheat. The values of sufficiency and threshold of toxicity in leaves were 0.13 and 1.15 μ Mo g^?1 dry matter of wheat.     

Cadmium Uptake by Winter Wheat Seedlings in Response to Interactions Between Phosphorus and Zinc Supply in Soils

ABSTRACT

Effects of application of zinc (Zn) (0, 1, 5, 10 mg kg^?1 soil) and phosphorus (P) (0, 10, 50, 100 mg kg^?1 soil) on growth and cadmium (Cd) accumulations in shoots and roots of winter wheat (Triticum aestivum L.) seedlings were investigated in a pot experiment. All soils were supplied with a constant concentration of Cd (6 mg kg^?1 soil). Phosphorus application resulted in a pronounced increase in shoot and root biomass. Effects of Zn on plant growth were not as marked as those of P. High Zn (10 mg kg^?1) decreased the biomass of both shoots and roots; this result may be ascribed to Zn toxicity. Phosphorus and Zn showed complicated interactions in uptake by plants within the ranges of P and Zn levels used. Cadmium in shoots decreased significantly with increasing Zn (P < 0.001) except at P addition of 10 mg kg^?1. In contrast, root Cd concentrations increased significantly except at Zn addition of 5 mg kg^?1 (P < 0.001). These results indicated that Zn might inhibit Cd translocation from roots to shoots. Cadmium concentrations increased in shoots (P < 0.001) but decreased in roots (P < 0.001) with increasing P supply. The interactions between Zn and P had a significant effect on Cd accumulation in both shoots (p = 0.002) and roots (P < 0.001).     

INTERACTIVE EFFECTS OF SALINITY AND PHOSPHORUS NUTRITION ON PHYSIOLOGICAL RESPONSES OF TWO BARLEY SPECIES

Salinity is one of the most important agricultural problems in Iran. The effect of different levels of salinity and phosphorus on shoot length, root and shoot fresh and dry weight, nutrient elements (sodium (Na⁺), potassium (K⁺), phosphorus (P) and chloride (Cl^?), proline and soluble sugar contents of barley were investigated. Two cultivars of barley, Hordeum murinum (wild resistant germplasm) and Hordeum vulgar, variety Afzal were treated in vegetative stage under hydroponics condition in a factorial arrangement based on completely randomized block (CRB) design with four levels of salinity [0, 100, 200 and 300 mM sodium chloride (NaCl)] and three levels of phosphorus (15, 30 and 55 μm L^?1) with three replications. By increasing salinity, all the measured parameters, except sodium (Na⁺) content were reduced. Furthermore, with increased in phosphorus levels from 15 to 55 μm, Na⁺ content of the plant shoots decreased, but length, fresh and dry weights of roots and shoots and K⁺, P, Cl^?, proline, and soluble sugars content of the shoots increased. The results indicated that accumulation of mineral ions for osmotic adjustment and restriction of Na⁺ accumulation in shoots were involved in phosphorus enhancement of the salt tolerance of barley. Thus, it seems that in saline soils, where there is no possibility for soil leaching and amending, application of phosphorus fertilizers can lead to a satisfactory growth and production in barely yield.     

EFFECT OF LANTHANUM ON RICE PRODUCTION,NUTRIENT UPTAKE,AND DISTRIBUTION

ABSTRACT

Split root solution culture experiments were conducted to study the effects of the rare earth element lanthanum (La) on rice (Oryza sativa) growth, nutrient uptake and distribution. Results showed that low concentrations of La could promote rice growth including yield (0.05 mg L^?1 to 1.5 mg L^?1), dry root weight (0.05 mg L^?1 to 0.75 mg L^?1) and grain numbers (0.05 mg L^?1 to 6 mg L^?1). High concentrations depressed grain formation (9 mg L^?1 to 30 mg L^?1) and root elongation (1.5 mg L^?1 to 30 mg L^?1). No significant influence on straw dry weight was found over the whole concentration range except for the 0.05 mg L^?1 treatment. In the pot and field experiments, the addition of La had no significant influence on rice growth.Lanthanum had variable influence on nutrient uptake in different parts of rice. Low concentrations (0.05 mg L^?1 to 0.75 mg L^?1) increased the root copper (Cu), iron (Fe), and magnesium (Mg), and grain Cu, calcium (Ca), phosphorus (P), manganese (Mn), and Mg uptake. High concentrations (9 to 30 mg L^?1) decreased the grain Ca, zinc (Zn), P, Mn, Fe and Mg, and straw Ca, Mn, and Mg uptake. With increasing La concentration, root Zn, P, Mn, Cu, and Ca concentrations increased, and grain Ca and Fe, and straw Mn, Mg, and Ca concentrations decreased. Possible reasons are discussed for the differences between the effects of La in nutrient solutions and in pot and field experiments.     

ALLEVIATION OF CADMIUM-TOXICITY BY APPLICATION OF ZINC AND ASCORBIC ACID IN BARLEY

ABSTRACT

Effect of cadmium (Cd) on biomass accumulation and physiological activity and alleviation of Cd-toxicity by application of zinc (Zn) and ascorbic acid in barley was studied, using semisolid medium culture including 15 treatments [four Cd concentration treatments: 0.1, 1, 5, 50?µmol?L^?1, four treatments with addition of 300?µmol?L^?1 Zn or 250?mg?L^?1 ascorbic acid (ASA) based on these four Cd concentrations, respectively, and three controls: basic nutrient medium, and with Zn or ASA, respectively]. Cadmium addition to semisolid medium, at a concentration of 1, 5, and 50?µmol?L^?1, inhibited biomass accumulation and increased malondialdehyde (MDA) content of barley plants, while the addition of 0.1?µmol?L^?1 Cd increased slightly dry mass. There was a tendency to a decrease in Zn, copper (Cu) concentrations both in shoots and roots and iron (Fe) in shoots of barley plants exposed to 1 to 50?µmol?L^?1 Cd. In addition, there were indications of a stress repose characterized by increased superoxide dismutase (SOD) and peroxidase (POD) activities relative to plants not subjected to Cd. The physiological changes caused by Cd toxicity could be alleviated to different extent by application of 300?µmol?L^?1 Zn or 250?mg?L^?1 ASA in Cd stressed plants. The most pronounced effects of adding Zn or ASA in Cd stressed medium were expressed in the decreased MDA and increased biomass accumulation, e.g., MDA contents were reduced (p≤0.01) by 4.8%–17.8% in shoots and 0.5%–19.7% in roots by adding 300?µmol?L^?1 Zn, in 50?µmol?L^?1 Cd stressed plants, and by 1.3%–7.4% in shoots and 2.6%–4.5% in roots by application of 250?µmol?L^?1 ASA, respectively. However, ASA addition may enhance Cd translation from root to shoot, accordingly, ASA would be unsuitable for the edible crops grown in Cd contaminated soils to alleviate phytotoxicity of Cd.     

Effects of humic acids and herbicides,and their combinations on the growth of tomato seedlings in hydroponics

The morphology and length of roots and shoots of tomato (Lycopersicon esculentum Mill.) seedlings grown on a nutrient medium for fourteen days in a controlled environment chamber were apparently not affected, whereas the dry matter content of roots was significantly enhanced when 200 mg L^?1 of humic acid (HA) isolated from either a non-amended soil or a sewage-sludge-amended soil was present in the nutrient medium. In contrast, the HA-like fraction isolated directly from the sewage sludge caused, under the same conditions, extensive alterations of tomato morphology and a significant reduction of the length and dry weight of both shoots and roots. The presence in the nutrient medium of the herbicides alachlor or imazethapyr at concentrations of 1 and 0.01 mg L^?1, respectively, caused a marked decrease of tomato root and shoot length and dry weight. Differently, the herbicide rimsulfuron at a concentration of 0.01 mg L^?1 produced a slight decrease in shoot and root length and a slight increase in their dry weight. A combination of 200 mg L^?1 soil HA and each of the herbicides alachlor, rimsulfuron and imazethapyr at concentrations of 1, 0.01 and 0.01 mg L^?1, respectively, in the nutrient medium attenuated the growth depression of tomato shoots and roots observed in the presence of the herbicide alone. However, the simultaneous presence of sewage sludge HA and any herbicide in the nutrient solution caused negative synergistic effects on tomato growth. The volume of nutrient solution and the amount of electrolytes taken up by tomato plants during the growth experiments correlated highly significantly with the total plant dry weight. Tomato seedlings induced a pH decrease in the nutrient medium in all treatments except in those where sludge-HA was present, either alone or in combination with any herbicide.     

Alleviation of cadmium phytotoxicity by magnesium in Japanese mustard spinach

Abstract

To clarify the mechanism of Magnesium (Mg) in alleviating cadmium (Cd) phytotoxicity, Japanese mustard spinach (Brassica rapa L. var. pervirdis) was grown for 10 days after treatment in hydroponics in a growth chamber under natural light. The treatments were: (1) nutrient solution alone (Control), (2) 10 mmol L^?1 Mg (High-Mg), (3) 2.5 µmol L^?1 Cd (Cd-toxic), (4) 2.5 µmol L^?1 Cd plus 10 mmol L^?1 Mg (Mg-alleviated). The Cd-toxic treatment showed substantial growth retardation and chlorosis of young leaves, such symptoms were not observed in Mg-alleviated plants. Magnesium-alleviated plants showed higher shoot growth, more than twofold, and decreased shoot Cd concentration, approximately 40%, compared with Cd-toxic plants. This increase in shoot growth and simultaneous decrease in shoot Cd concentration may explain the alleviation of Cd toxicity with Mg in Japanese mustard spinach. In Cd-toxic plants, concentrations of K in shoots and Zn in both shoots and roots increased compared with the other three treatments. Concentrations and accumulations of Fe and Mn in shoots decreased significantly in the Cd-treated (Cd-toxic and Mg-alleviated) plants compared with the control and High-Mg plants. Thus, the application of high amounts of Mg in the nutrient solution can alleviate Cd toxicity in plants.     

EFFECT OF PHOSPHORUS APPLICATION ON HIERARCHICAL LATERAL ROOT MORPHOLOGY AND PHOSPHORUS ACQUISITION IN SOYBEAN

Root growth systems are hierarchical and sensitive to nutrient availability in soil. Lateral roots are an important component of plant root morphology. Phosphorus (P) availability regulates root branching in plants such as Arabidopsis thaliana, barley (Hordeum vulgare), and rice (Oryza sativa L.). However, little information is available for soybean (Glycine max L.). A pot experiment was conducted to determine the morphological characteristics of lateral roots of different orders and P acquirement of soybean seedlings under three levels of applied P of 0, 50 and 100 mg P kg^?1 soil. Root length, an important parameter of root characteristics, differed in four orders. Lateral roots in the second and third order contributed 39.4 and 34.2% of total root length, respectively. Moreover, since most of lateral roots were fine roots (roots having a diameter 0.5 mm), fine roots had a frequency distribution of 58.5 to 61.4% in the second and third orders. Phosphorus application significantly increased dry weight, total length and number of lateral roots in the four orders with the ranking of fourth > third > second > first (P ≤ 0.05), but did not affect the average length of a lateral root. Phosphorus application reduced the frequency distribution of fine lateral roots in the first and second orders, while increased in the third and fourth orders (P ≤ 0.05). Compared with the medium P application (50 mg P kg^?1 soil), the high P application (100 mg P kg^?1 soil) inhibited lateral root growth with decreases in root dry weight, root length and root number at all orders. Phosphorus concentration and content increased with the increase in P application. The correlation between characteristics of lateral root and P status in the plants varied among root orders. The length of lateral roots from first to third order had a positive correlation with P concentration in root and shoot, and had a good relationship with P content. Lateral root numbers at the second, third and fourth orders were significantly correlated with P content while no correlation was found with the average length of a lateral root. It is proposed that the main effect of P application appears to be on the lateral root initiation rather than on lateral root elongation, and P favors the lateral root formation of the higher orders. The total length and number of lateral root at the second and third orders play a more important role in P content than those at other lateral root orders.     

DYNAMICS OF NITROGEN AND PHOSPHORUS PARTITION IN FOUR OLIVE TREE CULTIVARS DURING BUD DIFFERENTIATION

Variations of nitrogen and phosphorus levels in reproductive shoots and their leaves of self-rooting olive (Olea europaea) cultivars ‘Amfissis’ (A), ‘Kalamon’ (K), ‘Manzanillo’ (M), and ‘Chalkidikis’ (C) were monitored from the end of harvest until the emergence of the inflorescences. This 90-days period was divided into three sub-periods: before (pre-BD), during (BD), and after (post-BD) bud differentiation. The nitrogen (N)-content in leaves of the reproductive shoots varied between 10–20 mg g^?1 and among cultivars the order of decreasing concentration levels was C > K > A > M. The N-content in reproductive shoots varied between 6–14 mg g^?1 (K > A > C > M). Patterns of time-course variations are presented. Partitioning of N between leaves and shoots (N_L:N_S) varied with time, with a ratio between 1.5–2. The fluctuations in the N_L:N_S ratio over the 90 days showed two distinct phases: during pre-BD either increased (‘Amfissis’ and ‘Chalkidikis’) or remained relatively constant (‘Kalamon’ and ‘Manzanillo’), while during BD and post-BD decreased in all cultivars. The order of decreasing N_L:N_S ratio among cultivars was K > C > M > A.

Phosphorus (P) content in leaves of the reproductive shoots varied between 0.1–2.5 mg g^?1, (A > C > K > M). Phosphorus content in reproductive shoots varied between 0.2–1.6 mg g^?1, with the highest levels in ‘Amfissis’ compared to the other cultivars. Patterns of P partitioning between leaves and shoots were similar in all cultivars. The P_L:P_S ratio varied between 0.9–2 (A > C > K > M).

The N:P ratio varied between 5:1–20:1 in reproductive shoots and 10:1–35:1 in their leaves, increasing over the examined period. The increase rate of the N:P ratio varied between the three sub-periods, the lowest rate being during BD. The pattern of changes in the N:P ratio was similar in both leaves and shoots and an increase of N:P ratio in leaves was highly correlated with the corresponding increase of N:P in shoots.     

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.     

Stress Induced by Heavy Metals Cd and Pb in Bean (Phaseolus Vulgaris L.) Grown in Nutrient Solution

The increasing number of cases of soil contamination by heavy metals has affected crop yields, and represents an imminent risk to food. Some of these contaminants, such as cadmium (Cd) and lead (Pb), are very similar to micronutrients, and thus can be absorbed by plants. This study evaluated the translocation of increasing amounts of cadmium and lead and the effects of these metals in the production of beans. Bean plants were grown in nutrient solution Clark and subjected to increasing levels of Cd (from 0 to 0.5 mg L^?1) and Pb (from 0 to 10 mg L^?1). Cadmium concentration of 0.1 mg L^?1 translocated 39.8% to the shoot, and dry matter production was reduced by 45% in shoots and 80% in roots, compared to the control treatment. Lead showed impaired movement in the plant, however the concentration of 1.0 mg L^?1 was observed in 5.7% of metal translocation to the leaves. The concentration of 10 mg L^?1 Pb reduced dry matter production of roots and shoots in 83% and 76%, respectively, compared to the control treatment.     

EFFECT OF ARSENIC ON GERMINATION,PHOTOSYNTHESIS AND GROWTH PARAMETERS OF TWO WINTER WHEAT VARIETIES IN IRAN

□ Effects of different arsenic (As) concentration (0–30 mg L^?1) on seed germination, root tolerance index, relative shoot height, root and shoot biomass, photosynthetic pigments and arsenic accumulation in two wheat varieties were investigated. Low concentrations of arsenic (0–2.5 mg L^?1) stimulated germination percentage, shoot and root elongation, plant biomass as well as chlorophyll content as compared with control, however, these factors all decreased gradually at high concentrations of arsenic (5–30 mg L^?1). ‘Zarin’ variety had a significantly higher tolerance to arsenic than ‘Sardari.’ Arsenic accumulation by plants root and shoot increased with the increasing arsenic concentrations in medium, which ‘Zarin’ had a higher ability to absorb and translocate arsenic to the shoots. Root accumulated more arsenic than shoot. The similar trend of chlorophyll content and wheat growth under different arsenic concentration suggesting that arsenic toxicity affects the photosynthesis which ultimately results in the reduction of wheat growth and yield.     

EFFECTS OF CONVENTIONAL AND CONTROLLED RELEASE PHOSPHORUS FERTILIZER ON CROP EMERGENCE AND GROWTH RESPONSE UNDER CONTROLLED ENVIRONMENT CONDITIONS

A series of experiments on the effects of form and rate of seed row placed phosphorus (P) fertilizer were carried out under controlled environment conditions using flats of a P-deficient Brown Chernozemic soil from Saskatchewan, Canada. The experiments were conducted in the laboratory and growth chamber using rates of seed row placed granular P fertilizer up to 100 kg P₂O₅ ha^?1. Two forms of monoammonium phosphate fertilizer were compared: 1) conventional MAP granules and 2) controlled release phosphorus (CRP) fertilizer granules (Agrium Inc, Denver, CO, USA.) made with a polymer coating to slow the release of phosphate to soil solution. Six crops were utilized in the study to provide a range of commonly grown cereal, oilseed, pulse and forage crops in Western Canada: wheat (Triticum aestivum), canola (Brassica napus), mustard (Brassica juncea), flax (Linum usitatissimum), yellow pea (Pisum sativum) and alfalfa (Medicago sativum). Parameters measured were percentage of planted seeds that had emerged after two weeks, plant biomass yield, and plant P uptake after four weeks. Most of the crops tested showed no negative impact on emergence with seed row placed conventional P fertilizer at rates up to ～20 to 30 kg P₂O₅ ha^?1. Pea, flax and mustard tended to be most sensitive to injury from high rates of seed placed MAP while wheat was least sensitive. The controlled release phosphorus fertilizer (CRP) product greatly increased the tolerance of crops to high rates of seed row placed P, with rates of 80 kg P₂O₅ ha^?1 placed in the seed row producing no significant injury for most crops. This effect is attributed to the coating reducing the harmful salt effect that occurs when high rates of fertilizer are placed in the seed row in close proximity to the seed. Generally, a rate of 30 kg P₂O₅ ha^?1 was sufficient to produce maximum early season biomass yield and P uptake for both conventional MAP and CRP fertilizers. Large differences in early P availability were not evident between the conventional P and controlled released P fertilizer products.     

Genotypic differences in effects of cadmium on growth and nutrient compositions in wheat

Abstract

A solution culture study was conducted to determine the genotypic difference in the effects of cadmium (Cd) addition on growth and on the uptake and distribution of Cd and other 11 nutrients in wheat plants. Cadmium addition at a rate of 1 mg L^?1 significantly reduced root and shoot dry matter production, shoot height, root length, chlorophyll content, and tillers per plant. On the average of 16 wheat genotypes used in study, Cd concentrations of Cd‐treated plants were 48.1 and 459 μg g^?1 dry weight (DW) in shoots and roots, respectively, and retained 77.91% of total Cd taken up in the roots. On the whole, Cd addition reduced the concentration of sulfur (S), phosphorus (P), magnesium (Mg), molybdenum (Mo), manganese (Mn), and boron (B), and increased iron (Fe), irrespective of the plant parts. The effect of Cd on the concentration of potassium (K), calcium (Ca), and copper (Cu) differed in shoots and roots. The significant difference existed among 16 wheat genotypes in their response to Cd in terms of growth and nutrient concentrations. Genotype E81513, which showed relatively less inhibition in growth, had the lowest shoot Cd concentration and more Cd accumulation in roots, while Ailuyuang had the highest Cd concentration and accumulation in shoot with lower Cd concentration in root. The significant interaction was found between Cd treatment and genotype for all nutrient concentrations in both shoot and root, except S and Zn in root.     

Copper Tolerance and Accumulation of Elsholtzia splendens Nakai in a Pot Environment

ABSTRACT

Elsholtzia splendens Naki has been identified as a copper (Cu) geobotanical indicator. In this study, the effects of Cu supply levels (control, 100, 200, 400, 600, 800, 1000, 1200 mg kg¹) on the growth and Cu accumulation in E. splendens were studied in one pot experiment. The results showed that no reduction in shoot height and dry weight was noted when the plants were grown at Cu supply levels up to 1000 mg kg^?1 in soil. Slight stimulation on shoot growth was noted at Cu levels ≥ 100 mg kg^?1. Copper concentration in shoots and roots increased with increasing Cu levels, and reached a maximum of 1751 and 9.45 mg kg^?1 (DW) at 1200 mg Cu kg^?1. The amount of Cu accumulated in the roots and shoots were 313 and 22 μ g plant^?1 at external Cu levels of 1000 and 800 mg kg^?1, respectively. The shoot/root Cu ratios ranged from 0.005 to 0.008 and more than 92% of the total Cu taken up by E. splendens was accumulated in roots. Furthermore, Cu concentrations in roots and shoots were significant and positively correlated with total soil Cu, water, ammonium nitrate (NH₄NO₃), ammonium (NH₄)-acetate, and ethylenediaminetetraacetic acid (EDTA) extractable Cu. These results indicate that E. splendens can considered as a Cu tolerant and accumulated plant, and root is the major part for accumulation of Cu in E. splendens.     

NUTRITIONAL DIAGNOSIS AND CORRECTION OF SHOOT DIEBACK OF RED BAYBERRY (MYRICA RUBRA SIEB. ET ZUCA)

Shoot dieback characterized by leaflet, rosette shoots, and dieback of shoot tips is one of the most important problems in red bayberry production in south China. However, the causes of shoot dieback have not been determined. The results of leaf analysis and correction experiment showed that leaf boron (B) concentrations were highly correlated with leaf area (P < 0.01), spring shoot length (P < 0.01), and spring shoot numbers sprouting from one old shoot (P < 0.05). Foliar application of B at 2.0 g L^–1 of borax was more effective on correcting shoot dieback than foliar application of Zn at 2.0 g L^–1 of zinc sulfate and of molybdenum (Mo) at 2.0 g L^–1 of ammonium molybdate. Boron application increased fruit yields by 1.23–2.15 times compared with the control. Shoot dieback resulted mainly from B deficiency in the red bayberry trees.     

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.