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.     

Micronutrient toxicity in buffalograss

The growth responses of buffalograss [Buchloe dactyloides (Nutt.) Engelm.] to elevated micronutrient levels in the fertilizer solution were investigated. Seedling plants established in peat‐lite mix in 11‐cm (0.6 L) pots in the greenhouse were irrigated with solutions containing 0.5, 1, 2, 4, 6, 8, or 12 mM of boron (B), chlorine (Cl), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), or zinc (Zn). The control solution contained (in μM): 20 B, 0.5 Cu, 40 Fe, 10 Mn, 0.5 Mo, and 4 Zn. A standard macronutrient concentration was used for all treatment solutions. Boron and Mo induced visual toxicity symptoms more readily than other micronutrients. Boron toxicity was characterized by chlorosis often accompanied by bleached leaf tips, while Mo toxicity resulted in leaf necrosis. The lowest levels that induced visual foliar toxicity were 0.5 mM B, 2 mM Cu, 4 mM Fe, 6 mM Mn, 1 mM Mo, and 4 mM Zn. Chloride did not induce foliar abnormalities in the concentration range tested. Biomass yield was reduced when the nutrient solution contained 2 mM B, 6 mM Cu, or 2 mM Mo. Elevated levels of Cl, Fe, Mn, and Zn did not alter dry matter yield. The relationship between the nutrient and tissue concentrations was determined for each microelement.     

Responses of cucumber grown in recirculating nutrient solution to gradual Mn and Zn accumulation in the root zone owing to excessive supply via the irrigation water

A standard and a high manganese (Mn) level (10 and 160 μM) were combined with a standard and a high zinc (Zn) level (4 and 64 μM) in the nutrient solution supplied to cucumber in closed‐cycle hydroponic units to compensate for nutrient uptake. The concentrations of all nutrients except Mn and Zn were identical in all treatments. The objectives of the experiment were to establish critical Zn and Mn levels in both nutrient solutions and leaves of cucumber grown hydroponically, to assess the impact of gradual Zn and/or Mn accumulation in the external solution on nutrient uptake and gas exchange, and to find whether Mn and Zn have additive effects when the levels of both ions are excessively high in the root zone. The first symptoms of Mn and Zn toxicity appeared when the concentrations of Mn and Zn in the leaves of cucumber reached 900 and 450 mg kg^–1 in the dry weight, respectively. Excessively high Mn or/and Zn concentrations in the leaves reduced the fruit biomass production due to decreases in the number of fruits per plant, as well as the net assimilation rate, stomatal conductance, and transpiration rate, but increased the intercellular CO₂ levels. Initially, the Mn or Zn concentrations in the recirculating nutrient solution increased rapidly but gradually stabilized to maximal levels, while the corresponding concentrations in the leaves constantly increased until the end of the experiment. The uptake of Mg, Ca, Fe, and Cu was negatively affected, while that of K and P remained unaffected by the external Mn and Zn levels. The combination of high Mn and Zn seems to have no additive effects on the parameters investigated.     

Micro nutrient toxicity in French marigold

The influence of elevated levels of micronutrients on the growth and flowering of French marigold (Tagetes patula L.) was investigated. Plants were grown with nutrient solution containing 0.25, 0.5, 1, 2, 3, 4, 5, or 6 mM boron (B), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), or zinc (Zn) and toxicity development was monitored. The threshold micronutrient concentrations that induced visible foliar toxicity symptoms were 0.5 mM B, 4 mM Cu, 4 mM Fe, 2 mM Mn, 1 mM Mo, and 5 mM Zn. The dry matter yields during the 5 week experimental period were reduced when micronutrient concentrations exceeded 0.5 mM B, 3 mM Cu, 3 mM Fe, 6 mM Mn, 0.5 mM Mo, and 5 mM Zn in the fertilizer solution. Leaf chlorophyll contents decreased when the nutrient solution concentrations of Cu, Fe, and Mn were greater than 0.5 mM, 3 mM, and 2 mM, respectively. Visual toxicity symptoms of the six micronutrients were characterized.     

Effect of chromium VI on mineral element composition of bush beans

Bush beans (Phaseolus vulgaris L. cv Contender) were grown on perlite with nutrient solution and 0, 1, 2.5 and 5 ppm levels of Na₂CrO₄ Significant decrease of top growth and chlorosis in trifoliated leaves were observed for 2.5 and 5 ppm Cr, with Cr concentrations (μg/g) in tops:≥ 12.1, in roots:≥ 509.9. Cr decreased K, Na, Mg and Fe concentrations, and increased P and Mn concentrations in roots. In tops decreased N, K, Na and Fe concentrations and increased Mn and Ca concentrations were observed, Translocation of P, Zn, Cu and Fe was inhibited; Ca and Mn translocation was generally enhanced. P/Fe ratio was increased up to 60% in chlorotic plants, indicating a shift from Fe²⁺ to Fe³⁺.     

铁和不同形态氮素对玉米植株吸收矿质元素及其在体内分布的影响 Ⅱ.对铁、锰、铜、锌等营养元素的影响

用营养液培养方法研究了铁和两种形态氮素对玉米植株吸收铁、锰、铜、锌等微量元素及其在体内分布的影响。结果表明:与硝态氮(NO₃^--N)相比,铵态氮(NH₄⁺-N)显著提高了玉米对铁的吸收,降低了对锰、铜及锌的吸收。供铁也明显提高了植株地上部铁的吸收总量,降低了锰及锌的吸收量,尤其是在供应No₃^--N时这种作用更为明显。在缺铁条件下,NH₄⁺-N处理的玉米新叶中铁的含量明显高于NO₃^--N处理;而新叶、老叶、茎中锰、锌、铜含量以及根中锰、锌含量都明显低于NO₃^--N处理。但使用NH₄⁺-N时,根中铜的含量较高。在供铁条件下,NH₄⁺-N处理的玉米植株四个不同器官中锰和锌的含量显著低于NO₃^--N处理的植株,而铜的含量正好相反。在缺铁条件下,玉米新叶中活性锰、活性锌的含量显著高于供铁处理;与NO₃^--N相比,NH₄⁺-N的供应也显著降低了玉米新叶中活性锰以及活性锌的含量。     

Effect of manganese on concentrations of Zn,K, Ca and Mg in two bush bean cultivars grown in solution culture

Two bush bean cultivars [Phaseolus vulgaris L. cv. ‘Wonder Crop 2’ (WC‐2) and ‘Green Lord’ (GL)], differing in Mn toxicity, were grown in a growth chamber for 12 days in Hoagland No. 2 nutrient solution containing 0.05 to 1 ppm Mn as MnCl₂4H₂O with 1 ppm Fe as Fe‐EDTA, at an initial pH 5.00. Concentrations of Zn, K, Ca and Mg in the tissues of two bush bean cultivars were examined in relation to Mn toxicity.

The concentration of Zn in the leaves of Mn‐sensitive WC‐2 increased significantly with increasing Mn concentration in the solution, but such levels were not toxic to the plants.

The percent distribution of Zn and K in Mn‐sensitive WC‐2 plants (% of total uptake) significantly increased in the tops and decreased in the roots with increasing Mn concentration in the nutrient solution; however, Mn treatment had no effect on distribution of either Ca or Mg in WC‐2. External Mn concentration had little or no effect on the K, Ca, or Mg concentration in the tops of Mn‐tolerant GL.     

Response of bean micronutrient nutrition to arsenic and salinity

The effects of different levels of arsenic (As) and salinity on bean plant (Phaseolus vulgaris L., cv. Buenos Aires) nutrition were investigated. We studied the processes of absorption and accumulation of chloride (Cl) and micronutrient elements: boron (B), copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn). The experiment was performed in soilless culture at two levels of As: 2 and 5 mg As L^‐1 [added as sodium arsenite (NaAsO₂)], and three saline levels [only sodium chloride (NaCl) was added]: 1, 2, and 4 dSm^‐1. Sodium arsenite and NaCl significantly affected micronutrients allocation within the bean plant at levels used in this study. Arsenite depressed Mn and Cl concentrations in the root, whereas root B, Cu, and Zn levels were increased. Boron, Cu, Fe, and Cl concentrations were significantly higher in As‐stressed plants compared with controls. The addition of NaCl increased the Cl and Mn concentrations in roots and Cl, Fe, and Mn in leaves.     

Nitrate/ammonium ratio effects on mineral element uptake by sorghum 1

Abstract

Experiments were conducted using different NO₃ ^–/NH₄ ⁺ ratios to determine the effects of these sources of N on mineral element uptake by sorghum [Sorghum bicolor (L.) Moench] plants grown in nutrient solution. The NO₃ ^–/NH₄ ⁺ ratios in nutrient solution were 200/0, 195/5, 190/10, and 160/40 mg N L^–1. Nutrient solutions were sampled daily and plants harvested every other day during the 12‐day treatment period.

Moderately severe Fe deficiencies were observed on leaves of plants grown with 200/0 NO₃ ^–/NH₄ ⁺ solutions, but not on the leaves of plants grown with the other NO₃ ^–/NH₄ ⁺ ratios. As plants aged, less Fe, Mn, and Cu were translocated from the roots to leaves and leaf/root ratios of these elements decreased dramatically in plants grown with 200/0 NO₃ ^–/NH₄ ⁺ solutions. Extensive amounts of Fe, Mn, and Cu accumulated in or on the roots of plants grown with 200/0 NO₃ ^–/NH₄ ⁺ solutions. Manganese and Cu may have interacted strongly with Fe to inhibit Fe translocation to leaves and to induce Fe deficiency. As the proportion of NH₄ ⁺ in solution increased, K, Ca, Mg, Mn, and Zn concentrations decreased in the leaves, and Ca, Mg, Mn, and Cu concentrations decreased in roots. Potassium and Zn tended to increase in roots as NH₄ ⁺ in solution increased.     

Manganese toxicity in bush bean as affected by concentration of manganese and iron in the nutrient solution

An experiment was conducted to clarify the relationship between Mn toxicity and Fe deficiency in bush snap bean (Phaseolus vulgaris L. cv. ‘Wonder Crop No. 2'). Seedlings were grown in full strength Hoagland No. 2 solution at pH 6.0 for ten days. Six concentrations of Mn as MnCl₂.4H₂O were used in combination with three concentrations of Fe as FeEDTA.

Toxicity symptoms, induced by low levels of Mn (0.1 ppm and above), included: small brown necrotic spots and veinal necrosis on primary leaves; necrosis on primary leaf petioles; interveinal chlorosis, with or without brown necrotic spots, on trifoliate leaves; and brown necrotic spots on stipules. Manganese toxicity symptoms were alleviated or prevented by increasing Fe concentration in the nutrient solution.

Manganese concentration in the leaves increased with increasing Mn and decreased with increasing Fe concentration in the nutrient solution, Iron concentration in the roots increased with increasing Fe concentration in the nutrient solution; however, Fe concentration in the leaves was not significantly affected by increasing Mn concentration in the solution culture. Manganese toxicity symptoms developed when Mn concentration in the leaves reached about 120 ppm.

A decrease in the Fe/Mn ratio in the nutrient solution resulted in a proportionate decrease in that of the leaves. Manganese toxicity symptoms occurred when the Fe/Mn ratio in the solution was 10.0 and below, or when the ratio in the leaves was less than 1.5. The ratio of Fe/Mn in the solution required for optimum growth of ‘Wonder Crop No. 2’ bean, without Mn toxicity symptoms, was in the range of 20.0 to 25.0.

Results indicate that the chlorosis on bush bean leaves induced by excessive Mn in the nutrient solution was due to excessive accumulation of Mn and not to Fe deficiency.     

IS CHLOROPHYLL FLUORESCENCE TECHNIQUE A USEFUL TOOL TO ASSESS MANGANESE DEFICIENCY AND TOXICITY STRESS IN OLIVE PLANTS?

A 130-day hydroponic experiment was carried out in a glasshouse to examine whether manganese (Mn) concentration in the nutrient solution affects the nutritional status of olive plants and to find out whether the chlorophyll fluorescence technique is suitable to assess Mn toxicity and/or deficiency stress in olive plants prior to the appearance of these two nutritional disorders. For this purpose, chlorophyll fluorescence parameters (F_v/F_m and F_v/F₀ ratios) were recorded every 40 days in the leaves of ‘Kothreiki’ and ‘FS-17’ olive cultivars, which were irrigated with Hoagland's nutrient solutions containing various Mn concentrations. In parallel the elongation of the main shoot of all experimental plants, as well as the concentrations of Mn, iron (Fe), zinc (Zn), boron (B), phosphorus (P), calcium (Ca), magnesium (Mg), and potassium (K) in their leaves were recorded. The following Mn treatments were applied: 0 μM Mn (to induce Mn deficiency), 40 μM Mn (to promote normal growth), and 640 μM Mn (to induce Mn toxicity). Our results indicated that not only the rate of shoot elongation but also the fluctuation with time of the leaf concentrations of all determined mineral elements (except for Mn) was not significantly affected by the Mn concentration in the nutrient solution, irrespectively of the cultivar. This was not observed with regard to the time variation of the F_v/F_m and F_v/F₀ ratios, where the values of these parameters were significantly reduced in the 640 μM Mn treatment at the 80th and 130th day of the experiment in both olive cultivars, compared to the relevant previous ones (those of the days 0 and 40th), something which did not happen in the other two Mn treatments (0 and 40 μM). However, in none of the two cultivars tested and in any of the three Mn treatments (0, 40 and 640μM) the F_v/F_m and F_v/F₀ ratios did not drop below the critical values of 0.8 and 4, respectively, even at the end of the experiment, where high Mn concentrations were found in the leaves of both cultivars treated with 640 μM Mn (616 μg g^?1 d.w. in ‘FS-17’ and 734 μg g^?1 d.w. in ‘Kothreiki’). Symptoms of Mn toxicity (curling and brown speckles) were observed in the top leaves of both cultivars, after the 90th day of the experiment. At the same time, the final leaf Mn concentrations (those of the 130th day of the experiment) in plants grown under 0 μM Mn were 23 μg g^?1 d.w. in ‘FS-17’ and 20 μg g^?1 d.w. in ‘Kothreiki’, i.e., a little above of the deficiency range (<20 μg g^?1 d.w.). At the 130th day, Mn concentration in nutrient solution, as well as Mn concentration in the leaves of both olive cultivars was negatively correlated with the leaf concentration of Fe and the values of the F_v/F_m and F_v/F₀ ratios, and positively with the concentrations of Zn and P in the leaves. Finally, the periodical measurement of the F_v/F_m and F_v/F₀ ratios was proved to be a non-reliable means to predict the appearance of the visible symptoms of Mn toxicity in olive leaves (although their values declined significantly at the 80th and 130th day of the experiment in both olive cultivars).     

Zinc toxicity‐induced variation of mineral element composition in hydroponically grown bush bean plants

Bush bean plants (Phaseolus vulgaris L. cv Contender) were grown for twenty days in nutrient solution (pH=5), containing 0.13, 0.3, 0.5 or 0.75 mg 1^‐1 Zn as ZnSO₄‐7H₂O. The plant yield decreased linearly with the increase of the Zn concentration supplied. The phytotoxic threshold content (for 10% growth reduction) was about 486, 242, 95 and 134^‐ μg Zn g^‐1 for roots, steins, mature primary and trifoliate leaves, and developing leaves, respectively. High inverse correlation coefficients with the Zh concentration supplied were found for the Mn content of all organs, for the P content of roots, and for the Cu and Ca contents of developing leaves. Significant positive relations were found for the Fe, Zn and Cu contents in roots and for the Zn con‐ tents in stems and fully expanded leaves. The ratios of the mineral contents between organs suggest inhibition of uptake of Mn and P, and inhibition of translocation of Fe, Cu and Ca. The relation between dry weight decrease and Zn‐induced nutrient content disorders were discussed.     

GUIDE VALUES FOR ANTHURIUM (ANTHURIUM CULTORUM BIRDSEY) GROWN IN EXPANDED CLAY

Coefficients of variation and guide values of nutrients were determined for Anthurium cultorum Birdsey cvs. ‘Baron’, ‘Choco’, ‘Pistache’, ‘President’, ‘Midori’, and ‘Tropical’ grown in expanded clay (inert medium) using drip fertigation. Fully developed leaves after freshly-cut flowers were collected as index parts for chemical analyses at two-month intervals over the period of three years (2002–2004). Investigations were conducted at two specialized commercial farms, recording optimal yielding in terms of quantity and quality. A standard nutrient solution for anthurium hydroponics was used in fertigation. Mean guide values for six analyzed cultivars of Anthurium cultorum Birdsey are (in d.m. leaves): 1.40–1.70% nitrogen (N), 0.30–0.40% phosphorus (P), 3.60–4.50% potassium (K), 1.40–1.80% calcium (Ca), 0.20–0.30% magnesium (Mg), 0.30–0.40% sulfur (S), 46.0–60.0 ppm iron (Fe), 35.0–47.0 ppm manganese (Mn), 54.0– 72.0 ppm zinc (Zn), 5.10–6.50 ppm copper (Cu), and 64.0–83.0 ppm boron (B). Guide values for cvs. ‘Baron’, ‘Choco’, ‘Pistache’, ‘President’, ‘Midori’ and ‘Tropical’ are given in the text of this paper. A diversification was shown in guide values for analyzed cultivars in relation to certain macro- and microelements. Coefficients of variation were determined for nutrient contents in index parts of plants. A very high variation (%) was found for Mn 47.5 and Zn 41.8, high for Mg 38.5, P 32.6, S 30.6, medium for Fe 29.2, Ca 28.0, Cu 23.3 and B 20.3, while low for K 11.4 and N 9.9.     

Aluminum toxicity in tomato. Part 1. growth and mineral nutrition

Aluminum (Al) toxicity was studied in two tomato cultivars (Lycopersicon esculentum Mill. ‘Mountain Pride’ and Floramerica') grown in diluted nutrient solution (pH 4.0) at 0, 10, 25, and 50 μM Al levels. In the presence of 25 and 50 μM Al, significant reduction was found in leaf area, dry weight, stem length, and longest root length of both cultivars. Growth of ‘Floramerica’ was less sensitive to Al toxicity than growth of ‘Mountain Pride’. Elemental composition of the nutrient solutions were compared immediately after the first Al addition and four days later. The uptake of micronutrients copper (Cu), manganese (Mn), molybdenum (Mo), zinc (Zn), boron (B), and iron (Fe) from the nutrient solution was reduced in both cultivars with increasing Al levels. Nutrient solution Al gradually decreased in time for every treatment; less in cultures of ‘Floramerica’ than in ‘Mountain Pride’. Aluminum treatments decreased the calcium (Ca), potassium (K), magnesium (Mg), Mn, Fe, and Zn content in the roots, stems, and leaves. Aluminum treatment promoted the accumulation of P, Mo, and Cu in the roots, and inhibited the transport of these nutrients into stems and leaves. At 25 and 50 μM levels of Al, lower Al content was found in the roots of cv. “Floramerica’ than in the roots of cv. ‘Mountain Pride’.     

Effects of excess manganese on mineral uptake in mycorrhizal sorghum

Associations between vesicular‐arbuscular mycorrhizal (VAM) fungi and manganese (Mn) nutrition/toxicity are not clear. This study was conducted to determine the effects of excess levels of Mn on mineral nutrient uptake in shoots and roots of mycorrhizal (+VAM) and non‐mycorrhizal (‐VAM) sorghum [Sorghum bicolor (L) Moench, cv. NB9040]. Plants colonized with and without two VAM isolates [Glomus intraradices UT143–2 (UT1 43) and Gl. etunicatum UT316A‐2 (UT316)] were grown in sand irrigated with nutrient solution at pH 4.8 containing 0, 270, 540, and 1080 μM of added Mn (as manganese chloride) above the basal solution (18 μM). Shoot and root dry matter followed the sequence of UT316 > UT143 > ‐VAM, and shoots had greater differences than roots. Shoot and root concentrations and contents of Mn, phosphorus (P), sulfur (S), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), zinc (Zn), and copper (Cu were determined. The +VAM plants generally had higher mineral nutrient concentrations and contents than ‐VAM plants, although ‐VAM plants had higher concentrations and contents of some minerals than +VAM plants at some Mn levels. Plants colonized with UT143 had higher concentrations of shoot P, Ca, Zn, and Cu and higher root Mg, Zn, and Cu than UT316 colonized plants, while UT316 colonized plants had higher shoot and root K concentrations than UT143 colonized plants. These results showed that VAM isolates differ in enhancement of mineral nutrient uptake by sorghum.     

Elemental toxicity effects on germination and growth of pearl millet seedlings 1

Variability in millet stands in West Africa is clearly visible as early as three weeks after planting. The objectives of this study were to determine the influence of pH and chemical toxicities on millet germination and seedling growth and to compare varietal tolerance of toxic conditions. A nutrient solution study was carried out with a series of Hoagland‐based nutrient solutions. Germination percentage was calculated, and root and shoot lengths were measured for one week. Critical values were determined for toxic elements. The only treatment which reduced germination percentage significantly was copper (Cu) concentrations >0.05M. Solution pH values between 5 and 7 resulted in the best root growth, though shoot growth was unaffected by pH. The roots were more sensitive than the shoots to several [aluminum (Al), boron (B), zinc (Zn)] of the elemental toxicities studied. Soil Al and manganese (Mn) levels may be high enough to have toxic effects on millet roots. However, natural soil iron (Fe), Cu, and Zn levels were much lower than the critical levels determined in the nutrient solution study. The improved varieties were more tolerant of Fe and Zn toxicity than the LOCAL variety, but the LOCAL variety was more tolerant of high B concentrations.     

Alfalfa Responses to Combined Use of Lime and Limiting Nutrients on an Acidic Soil

An on-farm field experiment was conducted on an acidic soil to investigate the effects of combined use of lime and deficient nutrients on herbage yield of alfalfa (Medicago sativa L.). Omitting lime and limiting nutrients led to elevated concentrations of aluminium (Al), iron (Fe), and manganese (Mn) in alfalfa leaves and stems and caused severe reductions in herbage yield of alfalfa. Combined use of lime (2 t ha^?1) and nutrients [phosphorus (P): 20 kg ha^?1, sulfur (S): 20 kg ha^?1, zinc (Zn): 4 kg ha^?1, and boron (B): 2 kg ha^?1] had the maximum increase in groundcover, root biomass, nodulation, leaf retention, leaf-to-stem ratio, herbage yield, crude protein, and nutrient composition of alfalfa. These beneficial effects were due to raised soil pH; improved calcium (Ca), P, S, Zn, and B nutrition; and reduced Al, Mn, and Fe toxicity. Aluminium and all the nutrients except copper (Cu) were more concentrated in alfalfa leaves than stems.

Aluminum concentration was about three times greater in the lower leaves than in upper leaves. Lower leaves also had much greater concentrations of Ca, Mg, K, S, Fe, Mn, Cu, and B compared with upper leaves. In contrast, P and Zn concentrations were greater in the upper leaves than in lower leaves. Results suggest that the combined use of lime and all the limiting nutrients may realize potential beneficial effects of alfalfa on acidic soils where more than one essential nutrient is deficient. This may increase growth potential, nitrogen contributions, and groundcover by alfalfa and reduce soil erosion and runoff.     

Critical nutrient concentrations and antagonistic and synergistic relationships among the nutrients of NFT‐grown young tomato plants

Critical concentrations of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), zinc (Zn), and manganese (Mn) with respect to dry matter yield end antagonistic and synergistic relationships among these nutrients were studied in which tomato (Lycopersicon esculentum L.) was grown in recirculating nutrient solution (NFT). Increments of nutrient elements in the nutrient solution increased the proportional rate of the corresponding nutrient elements. Increasing levels of N negatively correlated with plant P and positively correlated with Ca, Fe, and Zn. Iron and Mn contents of the plants were increased and N, K, Ca, and Mg were decreased as a function of P applied. Increases in K in the nutrient solution caused increases in the concentrations of K, N, P, and Zn, and decreases in the concentration of Ca and Fe. Applied Ca increased the concentrations of Ca and N, and decreased the concentrations of P, Mg, Fe, Zn, and Mn. Potassium, Ca, and Fe contents of the plants were decreased and Zn increased, while N, P, and Mn were not affected by the increasing levels of external Mg. Iron suppressed the plant Mg, Zn, and Mn contents. Synergism between Zn and Fe was seen, while P, K, Ca, Mg, and Mn contents were not affected by Zn levels. Potassium, Ca, Mg, and Fe were not responsive to applied Mn, however, N and P contents of the plants were decreased at the highest levels of Mn.     

The response of okra to molybdenum in sandculture

Abstract

The role of molybdenum in plant growth was examined by growing ‘Emerald’ okra (Abelmoschus esculentus L. Moench) to fruiting in sand‐culture.

Molybdenum treatment lower than 1 ppm, resulted in leaves that were generally pale yellow and curled upwards. At 1 ppm and 4 ppm Mo, plants were generally healthy with deep green leaves, while Mo application at 6 and 16 ppm resulted in stunted plant growth, deep green leaves, and dark brownish coating on the roots. Shoot/root ratio decreased with increasing rates of Mo. Total chlorophyll was unaffected by Mo application, whereas plant dry matter production and fruit yield were depressed at the 16 ppm Mo treatment.

Leaves of plants receiving less than 1 ppm Mo had higher concentrations of NO₃‐N, P, K, Ca and Mg than plants receiving above 1 ppm Mo treatments. The reverse was the case with the micronutrient levels. Specifically, Mo treatments higher than 1 ppm increased leaf‐Mo, ‐Fe, Mn and Zn and root‐Mo and Mn. The highest percentage of Fe and Mn, accumulated in the leaves, followed by the root and least in the wood, whereas the roots had the highest percentage of accumulated Mo, Cu and Zn. Leaf‐Mo was positively correlated with leaf‐Fe and Mn and root‐Mo and Mn. Molybdenum deficiency symptoms appeared in plants with leaf‐Mo of 5 ppm and treated with less than 1 ppm Mo. The 2 ppm Mo treatment with leaf‐Mo of 18 ppm produced normal and healthy plants, whereas. Mo application from 8 to 16 ppm with corresponding leaf‐Mo of 42 and 90 ppm Ho respectively produced plants that were severely stunted and had generally poor growth. The relatively high Ho concentration observed suggests that the okra plant is a Mo accumulator.     

Iron nutrition of sunflower(Helianthus annuus L.) as affected by various levels of p and ZN

The effects of various P and Zn levels on iron nutrition of sunflower (Helianthus annuus L.c.v. Record) were studied in two separate experiments in nutrient solution under greenhouse conditions.

In the first experiment, sunflower was grown in nutrient solutions containing four levels of P(1.5, 2.5, 3.5 and 4.5 mM/l) and three levels of Fe(0.25, 0.75, and 1.5 ppm) as FeCl₃ or FeEDDHA. In the second experiment (following the first experiment), the treatments were three P levels (0.75, 1.50 and 3.00 mM/l), three Fe levels (0.25, 0.75 and 1.5 ppm) as FeEDDHA and three Zn levels (0.1, 0.2 and 0.4 ppm).

The plants receiving Fe‐chelate, except for 0.25 ppm Fe, showed no symptoms of iron chlorosis. With inorganic Fe treatments, iron chlorosis appeared after 7–10 days depending on P level, but except for 0.25 ppm Fe which remained chlorotic, plants recovered completely within 3–4 days thereafter due to pH regulating mechanism of sunflower under iron stress condition. With both sources of Fe, chlorosis was associated with high P:Fe ratio.

Increased P and Fe levels in nutrient solution resulted in general increases in the dry weights of roots and shoots. The Fe concentration of shoots, except in few instances, was not affected by P levels, indicating that the sunflower cultivar used in this experiment could utilize inorganic Fe as well as Fe‐chelate under our experimental conditions.

Increasing P levels caused significant increases in Mn content of the shoots as 0.25 and 0.75 ppm inorganic Fe³⁺. Increased Fe levels increased shoot Mn content with inorganic Fe and decreased it with Fe‐chelate. The effects of P, Fe and Zn on sunflower indicated an antagonistic effect of Zn on 1.5 ppm Fe for all P levels. Increased Zn levels in nutrient solution generally increased Zn content of the shoots without having any marked effect on their Mn content.