J. C. Brown

Iron Chlorosis in Plants

Publisher Summary A continuing supply of iron is essential to the welfare of the green plant. Any factor that interferes with absorption or utilization of iron may cause the plant to become iron deficient and chlorosis to develop. Iron chlorosis refers to the yellowing of plants, which can be alleviated by suitable iron compounds. Any factor that decreases the availability of iron in a soil or competes in the absorption process contributes to iron chlorosis. Thus, phosphate, bicarbonate, and calcium salts in growth media have often been mentioned as contributing to some type of chlorosis. The iron compounds in soils of humid regions come from the weathering of many iron-containing minerals of the parent material. Two extremes are represented by podzolic and lateritic soils.

Manganese and iron toxicities dependent on soybean variety

Abstract Tolerances to Fe and Mn were determined with Bragg and Forrest (Mn‐intolerant) and T203 and Lee (Mn‐tolerant) soybean (Glycine max. (L.). Bragg was Fe efficient; Forrest and T203 were equally Fe‐inefficient plants. The soybeans were grown in nutrient solutions with 1.0 and 2.0 mg Fe/liter, and with 0.33 and 5.1 mg Mn/liter as variables, respectively. Bragg soybeans developed Fe toxicity symptoms with 2.0, but not with 1.0 mg Fe/liter. Forrest, Lee, and T203 did not develop Fe toxicity symptoms on either treatment. Bragg and Forrest soybean developed more severe Mn‐toxicity symptoms than Lee or T203 soybean when grown on nutrient solutions with 5.1 mg Mn/liter. Approach grafts showed that Mn tolerance appears to be controlled in the plant tops. Both Mn‐intolerant and tolerant soybean tops contained about the same concentration of Mn, but Mn‐tolerant tops contained more K and roots contained less Fe than Mn‐intolerant tops and roots. When Fe and Mn toxicities are not economically correctable, toler...

Differential mineral uptake by Maize Inbreds

Abstract Maize (Zea mays L.) inbreds were grown on soils known to produce Fe, Zn, Mg, Ca, and Cu deficiency and Al and Mn toxicity. The inbreds were assessed for their differential responses to the elemental problem induced by each soil. Marked differences in susceptibility and/or tolerance to limited or excess amounts of mineral nutrients were noted among the inbreds. Information on differential responses of plants to the various mineral elements should be beneficial for overcoming particular element problems and for developing plants which utilize mineral elements more efficiently.

Heavy‐metal toxicity in plants 1. A crisis in embryo

Abstract Heavy metals are often added indiscriminantly to soils in pesticides, fertilizers, manures, sewage sludges, and mine wastes, causing an imbalance in nutrient elements in soils. Heavy‐metal toxicity causes plant stress in various degrees dependent on the tolerance of the plant to a specific heavy metal. The objectives of this study were (i) to show that plant species and soils respond differently to heavy metals and (ii) to show the necessity for proper quantity and balance of heavy metals in soils for plant growth. Three Fe‐inefficient and three Fe‐efficient selections of soybean, corn, and tomato were grown on two alkaline soils with Cu and Zn ranging from 14 to 340 and Mn from 20 to 480 kg/ha. Heavy‐metal toxicity caused Fe deficiency to develop in these plants. The Fe‐inefficient T3238fer tomato and ys1/ys1 corn developed Fe deficiency on all treatments and both soils. T3238FER tomato (Fe‐efficient) did not develop heavy metal toxicity symptoms on any treatment or soil. The soybean varieties a...

Iron Chelates in Soybean Exudate

Soybean exudates contain iron compounds which can be separated electrophoretically into anodic bands and eluted with water. Chromatography of the water extracts separated iron from chelating agents which were identified as malic acid and malonic acid. Hence organic acids seem to function in the translocation of iron in plants.

Factors related to iron uptake by dicotyledonous and monocotyledonous plants. III. Competition between root and external factors for Fe.

Abstract In comparison studies (11, 12), monocotyledonous corn (Zea mays L.) and oats (Avena byzantina C. Koch) did not respond to Fe stress as effectively nor to the same degree as the dicotyledonous soybeans (Glycine max (L.) Merr.) or tomatoes (Lycopersicon esculentum Mill.). Both the Fe‐inefficient and Fe‐efficient corn and oats developed Fe chlorosis; the Fe‐efficient dicotyledonous plants were green. In the present study, the method of inducing Fe stress was changed to make it less severe. Instead of using only NO3‐N and no Fe to induce Fe stress (11, 12), both NH4‐N and NO3‐N were used along with varied concentrations of Fe. Iron stress was induced with BPDS (4,7‐diphenyl‐l, 10‐phenan‐throline disulfonic acid) and phosphate; both competed with the plant for Fe. Phosphate also inhibits reduction of Fe3+ to Fe2+ (12). This method of inducing Fe stress in the plants was less severe than using only NO3‐N and no Fe in the nutrient solutions and we were able to measure a difference in Fe‐stress response ...

Photochemical reduction of iron. II. Plant related factors

Abstract Photochemical reduction of ferric iron induced by ultraviolet (UV) and blue radiation is enhanced by certain di‐ and tri‐carboxylic acids. Iron photoreduction proceeds according to the following relative rates in Fe3+‐organic acid solutions containing the major plant acids listed: tartaric >oxalic>citric> malic>aconitic > fumaric ≥succinic≥FeCl3 (control). Any sensitized ferric to ferrous photoreduction occurring in plant foliage exposed to sunlight or artificial light would make iron more available to the tissues for metabolism. Iron is translocated within plants primarily complexed with citric acid (Tiffin, 1972). Citric acid is decarboxylated during Fe‐citrate photoreduction‐oxidation. Ferric iron photoreduction is thus accompanied by citrate degradation. In plant foliage, the fate of ferric citrate taken up the stem depends upon many plant‐related factors. Chelated iron is translocated predominately to actively growing regions where enzymatic reactions largely determine the immediate fate. In...

Differential iron chlorosis of oat cultivars ‐ a review

Abstract Markedly different iron chlorosis symptoms were observed among “winter” oat genotypes in field trials at Beevllle, Texas, during the 1975 and 1976 production seasons. An oat cultivar showing the most severe field chlorosis symptoms and one having no apparent chlorosis subsequently were grown in several iron‐deficient soils in the greenhouse and in controlled‐environment nutrient‐solution cultures to more critically study these Fe‐stress responses. TAM 0–312, the susceptible cultivar, exhibited severe Fe chlorosis symptoms in iron‐deficient soils in Texas greenhouse experiments and had a very dramatic response to soil treatment with either chelated or powdered metallic iron. In contrast, the “chlorosis resistant” cultivar, Coker 227, exhibited no chlorosis symptoms in the greenhouse experiments, and showed little response to soil treatment with Fe compounds. In controlled environment studies at the U.S.D.A. Plant Stress Laboratory, Beltsville, Maryland, Coker 227 was found to be much more efficien...

Absorption of Iron from Iron Chelate by Sunflower Roots

Roots of decapitated sunflower plants absorbed iron from the ferric chelate of ethylenediamine di(o-hydroxyphenylacetic acid), leaving most of the acid in the nutrient solution. The chelating capacity of the nutrient solution increased as iron was absorbed by the plants. Most of the absorbed iron was found in the plant exudate.

Role of calcium in micronutrient stresses of plants

Abstract When calcium carbonate was added to an acid soil, it induced or alleviated a micronutrient stress, depending on the genotype and the soil. Calcium carbonate added to Richland soil (pH 5.2) corrected Mn‐toxicity symptoms in Bragg soybean (Glycine max L.) Merr.) but induced B‐deficiency symptoms in Coker 71–5089 cotton (Gossypium hirsutum L.). The latter did not develop Mn‐toxicity symptoms. Absorption and transport of Ca may enhance P uptake and induce Fe‐deficiency symptoms on Fe‐inefficient genotypes. Cereals differ in their response to Cu stress and the degree to which Cu deficiency depresses the transport of Ca to top leaves affects the expression of the Cu‐deficiency symptoms (withertip). Manganese‐efficient oat genotypes took up more Ca than Mn‐inefficient oats. In contrast, Fe‐efficient oat genotypes took up less Ca than Fe‐inefficient oats. Calcium is universally important as a competing metal ion in chelation and transport of elements in plants and the differential uptake of Ca may affect...