44 research outputs found
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Effect of plant age on the form and amount of nitrogen uptake by greenhouse plants /
Strategies in a metallophyte species to cope with manganese excess
The effect of exposure to high Mn concentration
was studied in a metallophyte species, Erica
andevalensis, using hydroponic cultures with a range
of Mn concentrations (0.06, 100, 300, 500, and
700 mg L-1). At harvest, biomass production, element
uptake, and biochemical indicators of metal
stress (leaf pigments, organic acids, amino acids,
phenols, and activities of catalase, peroxidase, superoxide
dismutase) were determined in leaves and roots.
Increasing Mn concentrations led to a decrease in
biomass accumulation, and tip leaves chlorosis was
the only toxicity symptom detected. In a similar way,
photosynthetic pigments (chlorophylls a and b, and
carotenoids) were affected by high Mn levels. Among
organic acids, malate and oxalate contents in roots
showed a significant increase at the highest Mn
concentration, while in leaves, Mn led to an increasing
trend in citrate and malate contents. An increase of Mn also induced an increase in superoxide dismutase
activity in roots and catalase activity in leaves. As
well, significant changes in free amino acids were
induced by Mn concentrations higher than
300 mg L-1, especially in roots. No significant
changes in phenolic compounds were observed in
the leaves, but root phenolics were significantly
increased by increasing Mn concentrations in treatments.
When Fe supply was increased 10 and 20 times
(7–14 mg Fe L-1 as Fe-EDDHA) in the nutrient
solutions at the highest Mn concentration
(700 mg Mn L-1), it led to significant increases in
photosynthetic pigments and biomass accumulation.
Manganese was mostly accumulated in the roots, and
the species was essentially a Mn excluder. However,
considering the high leaf Mn concentration recorded
without toxicity symptoms, E. andevalensis might be
rated as a Mn-tolerant speciesinfo:eu-repo/semantics/publishedVersio
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Notes on Plant Nutrition
Plant nutrition is the study of absorption, translocation, and function of essential elements or nutrients in plants. Essential elements are chemical elements that meet criteria that determine that the elements are required for plant growth and development and therefore are called plant nutrients. Soil fertility is the study of delivery of essential elements from the soil to the plant. Soil fertility involves chemical, physical, and biological properties of soils. Some chemical properties of soil fertility are supply of plant nutrients and soil acidity. Some physical properties that affect soil fertility are texture, structure, depth, drainage, aeration, water, and temperature. Biological properties refer effects of organisms on soil fertility and may include harmful organisms such as diseases, insect pests, and weeds or beneficial organisms such as bacteria that conduct processes of mineralization and nitrification. It is difficult to sort properties of soil fertility into chemical, physical, and biological factors because of the interrelations and similarities of these factors
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Manganese toxicity in marigold as affected by calcium and magnesium
Iron/manganese toxicity disorder in marigold (Tagetes erecta L.) has been related to high concentrations of Mn and low concentrations of Ca and Mg in the affected leaves. Preplant addition of micronutrients in the media combined with constant feed program and low medium pH create favorable conditions for the development of Mn toxicity in greenhouse crops. Deficiency of Ca or Mg is due in part to low medium pH and to a lack of Mg and Ca in many of the fertilizers used in greenhouse production. The objectives of this research were to determine the relationship of Mn toxicity to the incidence of Fe/Mn toxicity disorder in marigold, and to evaluate the effect of low Mg supply and/or low Ca supply on the occurrence of the toxicity. Six experiments were conducted. Plants of Tagetes erecta L. ‘First Lady’ were started from seeds and then grown in solution culture supplying different concentrations of Mn, Ca and Mg depending on the objectives of each experiment. Symptoms were described for each experiment. When the plants were harvested, their dry weights were taken and their tissues were analyzed for Mn, Fe, Ca, and Mg concentrations. The symptoms of Mg deficiency included stunting, chlorotic and necrotic areas on the leaves. The symptoms of Ca deficiency included chlorosis and curling, especially of the new leaves. The symptoms of Mn toxicity included curled leaves, bleached patches and brown spots on the leaves. These symptoms of Mn toxicity are similar to those related to Fe/Mn toxicity disorder. The incipient deficiency solution concentration of Mg was 10 mg/l (internal incipient deficiency concentration was 1.5%). The incipient deficiency solution concentration of Ca was 20 mg/l (internal incipient deficiency concentration was 0.54%). The critical toxicity concentration of Mn was 4.5 mg/l (internal critical toxicity concentration was 270 mg/kg DW). Low Ca in solution (20 mg/liter) increased the sensitivity of marigold to high levels of Mn in solution by reducing the critical toxicity concentration of Mn from 4.5 to 0.5 mg/liter. Similar results were found when both Ca and Mg were low. Iron/manganese toxicity disorder can be attributed to Mn toxicity. Low Ca supply or low Ca and Mg supplies are factors favoring the occurrence of the disorder. Low Mg supply, alone does not seem to affect Mn toxicity in marigold. Based on this research, high Ca supply could alleviate the harmful effects of Mn toxicity in marigold. Low Mn supply could prevent the toxicity problems. Agricultural practices and nutritional regimes that reduce the availability of Mn and increase the availability of Ca could reduce the occurrence of Fe/Mn toxicity disorder in marigold and similar physiological disorders in other bedding plants grown in soilless media. Monitoring Mn supply and fertilizing with Ca could prevent or reduce Mn toxicity to floriculture plants