Leaf Tissue Mn Research Articles

Variable Manganese Rates Influence the Performance of Huanglongbing-affected Citrus Trees in Florida

Improving nutrient uptake and tree health play an important role in managing Huanglongbing (HLB)-affected citrus trees in Florida. A greenhouse experiment was conducted to evaluate the effect of increasing rates of manganese (Mn) on growth and development of sweet orange [Citrus sinensis (L.) Osbeck] trees at the University of Florida’s Institute of Food and Agricultural Sciences (UF/IFAS) Citrus Research and Education Center in Lake Alfred, FL. Half the trees were graft-inoculated with the HLB pathogen and the remainder were used as the HLB-free (non HLB) control trees. Four rates of Mn (0.0 kg·ha−1 Mn (Control), 5.6 kg·ha−1 Mn (1x—standard rate), 11.2 kg·ha−1 Mn (2x—standard rate), and 22.4 kg·ha−1 Mn (4x—standard rate) were split applied quarterly to both sets of the trees in a completely randomized design. There were seven single tree replicates for each treatment. Response variables measured were trunk diameter, tree height, leaf Mn concentration, plus above- and belowground biomass. The accumulated Mn in leaf tissues significantly increased trunk diameter but did not affect tree height for both HLB-affected and non-HLB trees, the 2x rate had the maximum value for trunk diameter relative to the 4x rate. This study established a positive correlation between soil available Mn with Fe and Cu, but negative correlation with B and Zn. A strong correlation of −0.76, −0.69, and 0.65 was observed between soil Mn and B, Zn, and Cu, respectively, as compared with 0.49 with Mn and Fe. Among HLB-affected trees, the 2x rate gave the most belowground dry matter, which was 3% greater than the control and 5% greater than 4x. Aboveground dry matter had at least 30% more biomass than belowground matter among all treatments within HLB-affected trees. For small and medium roots, Mn accumulation increased with Mn application until 2x rate and decreased thereafter for HLB-affected trees. The results from our study showed an Mn rate of 8.9–11.5 kg·ha−1 Mn, as the optimum Mn level for young ‘Valencia’ HLB-affected trees in Florida.

The Efficacy of Grafting on Alkali Stressed Watermelon Cultivars Under Hydroponic Conditions

The goal of the present study was to determine whether grafting of watermelon on gourd rootstocks could improve alkalinity tolerance and to investigate the physiological and morphological response mechanisms of the grafted plants under different pH levels. The experiment was carried out in a climate chamber to investigate growth, leaf chlorophyll content (SPAD), leaf area, stem length, shoot and root dry weight, root length, electrolyte leakage, leaf mineral composition, total chlorophyll and carotenoid contents. Two watermelon cultivars (Crimson tide, CT, and Crisby) were grafted onto three commercial Cucurbita maxima × C. moschata hybrid rootstocks under climate-chamber conditions (Strong tosa, ST, Ercole and Nun 9075). The grafted seedlings were transplanted onto 8 L continuously aerated pots containing nutrient solution with two different pH levels (8.5 and 6.5) and replicated three times. The results showed that in both grafted and non-grafted plants, there was a substantial reduction in shoot and root biomass production at high pH levels. At high pH level, the significantly highest leaf area, stem length, SPAD, concentration of P, Ca, S and Mn in leaf tissues were recorded in graft combination ‘Crisby/Ercole’, whereas the significantly highest concentration of Fe in leaf tissues, shoot dry weight were recorded in graft combination ‘Crisby/Nun 9075’. Moreover, at high pH, the significantly highest concentration of Mg and Cu in shoot under high pH levels was significantly found in graft combination of ‘CT/ST’. These results suggest that the use of interspecific Cucurbita maxima × C. moschata hybrid rootstocks can improve crop performance in watermelon plants under alkaline conditions.

Optimal Manganese Nutrition Increases Photosynthesis of Immature Pecan Trees

Southwestern U.S. pecan [Carya illinoinensis (Wangenh.) K. Koch] orchard soils are typically alkaline and calcareous, making micronutrients such as manganese (Mn) poorly available for root uptake. Manganese is essential to the light reactions of photosynthesis (Pn), but the level of leaf Mn for optimum Pn in pecan is unknown. Our objective was to characterize the relationships of foliar Mn fertilizer applications and leaf Mn nutrition with Pn over a broad range of leaf Mn concentrations. Two experiments were conducted from 2011 to 2012 (Expt. 1) and in 2013 (Expt. 2) in immature, nonbearing ‘Pawnee’ and ‘Western’ pecan orchards near Las Cruces, NM. To create differential leaf tissue Mn concentrations, four Mn spray concentrations were applied foliarly: 0.00, 0.34, 0.68, and 1.3 g Mn/L (Control, Low, Medium, and High, respectively). In Expt. 2, we added a higher Mn concentration (2.7 g Mn/L). Repeated measurements of leaf Pn were made beginning 1 week following a Mn application using a portable Pn system. Across treatments in both studies, final leaf Mn concentrations ranged from 21 to 1488 µg·g−1. Leaves treated with 0.68 g Mn/L had higher Pn than the other treatments in each experiment. In 2013, Pn rates of the leaves treated with 0.68 g Mn/L increased 7.1% and 10.4% over the Control for ‘Pawnee’ and ‘Western’, respectively. Our data confirm an association between leaf tissue Mn and Pn; the leaf tissue Mn concentration at which Pn rates are optimized in immature pecan trees was estimated to be 151.64 (±17.3 se) µg·g−1 Mn.

Manganese requirement for optimum photosynthesis and growth in NAD-malic enzyme C-4 species

Despite the evidence for a critical role of Mn in malate decarboxylation and CO2 release for carbon fixation reactions in C-4 plants, there is a lack of information on their Mn requirement. The objective of this study was to establish Mn levels needed for optimum growth and photosynthesis of four agriculturally important C-4 species, NAD-ME C-4 pearl millet and purple amaranth, and NADP-ME C-4 corn and sorghum, as compared to two C-3 species, wheat and squash. Plants were grown hydroponically in a complete nutrient solution with Mn concentrations ranging from 0 to 100 μM. We report that under these conditions, C-3 and NADP-ME C-4 plants reached their maximum biomass production with 2–5 μM Mn, the concentration commonly used in plant nutrient media. In contrast, Mn concentrations supporting maximum performance of NAD-ME C-4 plants were up to 20-fold higher and ranged between 50 and 100 μM. Although leaf tissue Mn concentrations increased in parallel with Mn nutrition in all plants, the higher leaf Mn had no effect on NADP-ME C-4 or C-3 plants, but it caused a large, up to 100%, increase in net photosynthetic rate in NAD-ME C-4 species. The highest photosynthetic rates across the spectrum of photon flux density were recorded for C-3 and NADP-ME C-4 plants receiving 2–5 μM Mn, and for NAD-ME C-4 species millet and amaranth supplied with 50 or 100 μM Mn, respectively. Squash (C-3) plants were the most sensitive to Mn and their photosynthetic rate was severely depressed with more than 10 μM Mn. The increase in photosynthetic rates of NAD-ME C-4 species occurred without an increase in stomatal conductance, eliminating CO2 uptake as the main cause. We propose that the higher photosynthetic rates in NAD-ME C-4 species supplied with higher Mn were a result of increased activation of the Mn-dependent NAD-ME in bundle sheath cells, producing greater CO2 supply for Calvin cycle reactions. This is, to our knowledge, the first report on a significantly higher Mn requirement for optimum photosynthesis and biomass production of NAD-ME C-4 species.

Use of XAS to Determine the Chemical Speciation of Bioaccumulated Manganese in Potamogeton pectinatus

AbstractManganese (Mn) accumulation was measured in Potamogeton pectinatus L. (sago pondweed) over a growing season. Leaf tissue Mn content increased from 120 mg kg−1 in June to 4990 mg kg−1 by October. Our objective was to chemically speciate bioaccumulated Mn in P. pectinatus with x‐ray absorption spectroscopy (XAS). Differences were found in Mn valence in leaf tissue between June, October, and January when compared to model inorganic Mn compounds. Manganese in June leaf tissue was most like [Mn2+ (H2O)6]. By October, average valence of Mn in leaf and root tissues was similar to Mn3O4. However, there was little agreement in the chemical structure of Mn in these tissues and Mn3O4. Senescent leaf tissue in January differed from October because the valence had shifted back toward Mn2+. The Mn3+ fraction had leached from leaf tissue between October and January. This coincided with a decrease in total Mn concentration during this same period. Manganese bioaccumulation in this aquatic species occurs in two phases: (i) Mn2+ is bound in finite sites and coordinated by water, (ii) once filled, Mn2+ is oxidized and stored as a Mn3+ oxide within the plant that can be leached upon senescence.

The effects of excess manganese on photosynthetic rate and concentration of chlorophyll in Triticum aestivum grown in solution culture

Manganese toxicity, which involves a broad array of physiological responses, has been identified as an important factor limiting plant growth on acid soils. In the experiments reported here, we examined the toxic effects of Mn on chlorophyll content, photosynthesis and respiration in two cultivars (Norquay and Columbus) of Triticum aestivum (wheat) which differ in tolerance of Mn. When grown over a range of concentrations of Mn (0–1 000 μM), the Mn‐tolerant cultivar maintained higher rates of photosynthesis and respiration, and higher concentrations of chlorophyll a and chlorophyll b, than did the Mn‐sensitive cultivar, despite greater accumulations of Mn in leaf tissues. After 5 days growth with 1 000 μM Mn in solution, the photosynthetic rate fell to 25% of control in the sensitive cultivar and to only 75% of control in the tolerant cultivar. The concentration of chlorophyll a fell to 50% of control in the sensitive cultivar, but did not differ from control in the tolerant cultivar. Greater effects were seen on concentrations of chlorophyll b. which fell to 35% and 55% of control in the sensitive and tolerant cultivars, respectively. Rates of photosynthesis decreased in both cultivars as concentrations of chlorophyll decreased; however, the photosynthetic rate per unit chlorophyll remained constant or increased in the tolerant cultivar and decreased in the sensitive cultivar as concentrations of Mn in solution increased. Thus, in the sensitive cv. Columbus, Mn seemed to have a toxic effect on both chlorophyll content and photosynthesis per unit chlorophyll. In the tolerant cv. Norquay, the only clear effect of Mn was a reduction in chlorophyll content, although direct inhibition of photosynthesis could not be discounted.

Manganese Oxidation Capacity of Homogenates of Cowpea [ Vigna unguiculata (L.) Walp.] Leaves Differing in Manganese Tolerance

Summary Dark-brown speckles on old leaves are manganese (Mn) toxicity symptoms in cowpea [Vigna unguiculata (L.) Walp)]. These speckles are deposits of brown substances found primarily in cell walls containing sensitivity Mn in an oxidized form, and their appearance is indicative of high Mn sensitivity of plant issue. In the present paper the hypothesis is tested that differences in leaf-tissue Mn tolerance owing to genotype, silicon (Si) concentration and leaf age are attributed to differences in Mn oxidation capacity of the leaf tissue. A Mn-sensitive and a Mn-tolerant cowpea genotype were precultured in complcomplete nutrient solution without and with Si (1400 μM) at optimum Mn supply (0.25 μM) for 17 days under controlled environmental conditions. Within 3 days of treatment with 10 μM Mn, Mn toxicity symptoms only appeared on older leaves of the Mn-sensitive genotype without Si supply. Homogenerates prepared from old and young leaves were incubated at 30 °C for 60 min either in the light or in the dark. Such homogenates had an extremely high potential to oxidize added and internal leaf Mn(II) in the light but not in the dark. Manganese oxidation could be described by enzyme kinetics with an apparent Km of approximately 0.5 mM Mn. Manganese oxidation capacity was higher in Mn-sensitive older leaves compared with Mn-tolerant younger leaves. However, no differences could be found between leaf tissues differing in Mn tolerance owing to genotype and Si status, which is not in aggrement with the working hypothesis. Therefore the results do not unequivocally support the hypothesis that high Mn leaf-tissue sensitivity is realted to high Mn(II) oxidation.

Effect of Soil Acidity and Magnesium on Muskmelon Leaf Composition and Fruit Yield

Abstract The response of muskmelons (Cucumis melo L.) to Mg fertilization and soil pH was studied on a Princeton loamy sand that contained 34 kg·ha−1 available Mg at pH 4.8. Calcitic limestone was used to adjust the soil to pH 5.4 in 1984 and 5.8 in 1985. Magnesium was added for 2 years at 0, 56, 112, and 168 kg·ha−1. Lime application increased exchangeable soil Ca and decreased exchangeable Mn. Liming had no effect on exchangeable Mg, but Mg application increased exchangeable Mg linearly. Plants developed Mg deficiency in plots receiving no Mg treatment regardless of soil pH and Mn toxicity in unlimed plots at pH 4.8. Leaves developed Mg deficiency symptoms when the Mg concentration in leaf tissue was 0.30%. Magnesium application increased leaf tissue Mg and reduced leaf tissue Mn concentrations. Application of calcitic limestone increased leaf tissue Ca and reduced leaf tissue Mg and Mn concentrations. Muskmelon fruit yields were increased both by liming and Mg applications. Yield increases due to liming were attributed to reduced Mn levels in plant tissue.

Residual Mn and associated soybean yield response from MnSO4 application on a sandy loam soil

A field experiment was initiated in 1977 to evaluate soybean (Glycine max (L.) Merr.) response to rates of broadcast Mn and was continued in 1978 to determine the residual effects of applied Mn. This study was conducted on a Dragston fine sandy loam soil with an initial pH of 6.0 and 2.5% organic matter. In 1977 the 40kg Mn/ha rate increased seed yields by 900 kg/ha and raised leaf tissue Mn concentration from 10.3 to 16.1 μg Mn/g. Residual Mn increased seed yield and leaf Mn concentration. Reapplied Mn produced higher yields and tissue Mn levels than the residual Mn. The Mitscherlich plant growth model r=0.67**, fit the relationship between yield and leaf Mn concentration. Double acid extractable Mn in soil sampled in 1978 was linearly related to broadcast Mn and soybean yields. Applied Mn increased Mn concentrations of soybean seed parts by 97%, 182% and 109% in the cotyledon, embryo and seedcoat, respectively.

Distribution of manganese in leaf tissues of manganese accumulator:Acanthopanax sciadophylloidesas revealed by Electronprobe X‐Ray Microanalyzer

Abstract The distribution of Mn in leaf tissues of a Mn accumulator: Acanthopanax sciadophlloides was investigated by means of electron‐probe X‐ray microanalysis using a scanning electron microscope in conduction with a cryostage. Unfixed and frozen plant specimens were used in this experiment. The results show that Mn is densely accumulated in the peripheral cells either of leaf, petiolule and petiole tissues. In the leaf tissues, Mn was highly concentrated in epidermis, palisade and spongy parenchyma cells. Considerable low Mn concentration was observed in vascular bundle cells. Distribution pattern of Mn in petiolule and petiole was similar and characteristic. In petiolule and petiole, most of the Mn was accumulated in the cell wall of epidermis, collenchyma and bundle sheath cells and least was in vascular bundle cells.

Effect of Mn on growth, modulation, and nitrogen fixation by soybeans grown in the greenhouse

Abstract Soybean (Glycine max (L.) Merr. cv Bragg) plants were grown in the greenhouse using a low‐Mn Leefield sand amended with 0, 2.5, 5, 20 and 50 yg Mn/g. The plants were inoculated and were primarily dependent on symbiotically fixed N. Measurements of DTPA‐extractable soil Mn, soil pH, leaf tissue Mn, top weight, top N content, and nodule weight, volume and number were made at 27, 42, 56, 63 and 69 days after planting. The DTPA extrac‐tant was a good predictor of leaf tissue Mn giving a highly significant (P = 0.01) overall correlation coefficient of 0.704 for this comparison. Because of an unexpected decline in soil pH from 6.8 to 6.0 and an associated increase in DTPA‐extractable Mn from 0.14 to 0.24 yg/g during preparation and handling prior to the first harvest time, Mn in the leaf tissue of the controls was never less than 21 yg/g. Since this concentration of Mn is above the deficient level, no significant responses in top growth, nitrogen fixation or nodule measurements were obtained from the a...

Influence of iron and pH on the yield and iron, manganese, zinc, and sulfur concentrations of carrots grown on sphagnum peat soil

In two greenhouse experiments, sphagnum peat, adjusted to various pH levels, was used to study the effect of various levels of Fe on the growth of carrots (Daucus carota L., var. sativa D.C.). The Fe was added to the medium as sequesterine 330 chelate. Maximum carrot root and top tissue yields were obtained at soil pH 6.6 and 7.1. At soil pH 5.2 and 7.8 the yields were in the intermediate range. The yields were low at pH 4.3, 4.5 and 8.1 and at pH 8.4 the carrots did not grow. The chlorotic symptoms on carrot leaves, accom-panied by reduced yields, were associated with 39 to 82 ppm Fe and > 332 ppm Mn in the leaf and were likely due to Mn toxicity. Toxic levels of Mn in tissue were found even at soil pH 8.1 and were associated with reduced carrot yields. The leaf tissue concentrations of Fe and Mn decreased as the pH of soil increased; however, at pH 5.2, 7.8, and 8.1 the tissue Mn concentration increased. The added Fe had no effect on the Fe concentration but decreased the Mn and Zn concentration of leaf tissue and increased carrot root yields. There was a significant interaction between added lime and Fe, whereby the decrease in leaf tissue Mn concentration and increases in root yields with added Fe were much greater at pH 4.5 and 5.2 than at pH values of 6.6 and 7.8. The S concentration in the leaf tissue decreased with added Fe and lime. The leaf tissue Zn concentrations of 184 to 490 ppm and S concentrations of 0.32 to 0.63%, as found here, are considered to be high but not in the toxic range.