Publisher Summary Zinc deficiency has been observed most extensively in the United States and Australia, but it occurs under field conditions in at least 20 different countries. Zinc deficiencies of plants are dramatic because of combinations of chlorosis, rosetting, dieback, and depressed or abnormal vegetative growth. It occurs on a variety of soils. Because zinc deficiency of plants is highly dramatic, it seems that it would have been identified long ago, but the rapid onset of the disease and the marked deterioration of affected plants were taken as evidence that the cause was not nutritional. Affected soils are usually of pH 6.0 or higher. Often they are sandy, although deficiencies have been found on fine-textured soils and on mucks and peats. Treatments with lime and phosphate fertilizers have been reported to induce zinc deficiencies in crops under some conditions. Old corral and barnyard sites often show zinc deficiencies.

The micronutrient cations iron, manganese, zinc, and copper: their uptake by plants from the adsorbed state

Zinc Deficiency and its Control

Publisher Summary The forms of Ni in soil are diverse and range from those of high activity (water-soluble and exchangeable forms) to ones that have no reactivity in the short term (the life of a plant). The reactions of Ni are dominated by sorption reactions on soil colloids whose nature, relative proportions, and concentrations are important. Soil pH plays a major role in these reactions and thus influences the availability of Ni to plants quite markedly; few other factors appear to be as significant as pH. Deficiency of Ni in plants is unlikely to be a practical problem, but toxicity is more likely. Interest in the occurrence of Ni toxicity is dominated by research on serpentine soils (ancient Ni) and soils to which large quantities of Ni have been added in wastes (modern Ni), particularly in the forms of sewage and sewage sludge. Much of the understanding of the forms and reactions of Ni in soils comes from experiments dealing with the chemistry and biology of these two extreme situations. Needless to say, caution is essential when attempting to determine what is normal. Future research on Ni in soil could fruitfully pursue, for example, the role of microbes in influencing the behavior of Ni, the fractionation of Ni in studies of weathering and reversion of active forms of Ni to less active ones, and the speciation of Ni in the soil solution and the extent and cause of temporal changes.

Forms, Reactions, and Availability of Nickel in Soils

Publisher Summary It is found that when manganese is supplied to plants in excessive amounts, it causes toxic symptoms. This chapter discusses manganese toxicity and the function of manganese in plants. The reactions of fundamental importance in higher and lower plant are described, while discussing the enzymatic reaction in which manganese may function as a cofactor. In addition, an attempt is made to connect the results of these enzymatic studies with those of plant physiological and bacteriological investigations. It has also been shown that manganese catalyzes not only various reactions of carbohydrate breakdown and organic acid metabolism, but also a number of important conversions involved in nitrogen metabolism and phosphorus metabolism. From the results of several investigations involving manganese toxicity, it has appeared that manganese toxicity is one of the main causes of soil acidity injury to plants. Aluminum toxicity and lack of available calcium, magnesium, or molybdenum may also affect plant growth in certain acid soils.

Soil Manganese in Relation to Plant Growth

The Ionic Composition of some Bog and Fen Waters in the English Lake District

Among the essential elements taken up by the roots none offers as troublesome a problem as iron with respect to its solubility in aqueous solutions. From the equilibrium constants for the reactions of iron ions with hydroxyl ions (11) it is apparent that the ferric iron concentration drops below one part per billion between the pH values of 4 and 5, and that it decreases by a factor of 1,000 for each unit increase of pH value. Ferrous iron is not very susceptible to precipitation as the hydroxide. However, in aqueous solutions in the presence of oxygen ferrous iron is thermodynamically unstable. Under atmospheric oxygen pressure the ferric ion is more stable in acid solutions, while at a basic pH the equilibrium favors ferrous iron (13). In order that ionic iron supply sufficient iron to the plants it is necessary that the minimum concentration required for adequate growth be no higher than the saturation concentration given by the solubility product. At a pH of 9 the saturation concentration of both cationic forms of iron drops below 10-20 M/liter in a solution in equilibrium with atmospheric oxygen. Since on many occasions plants do not suffer from iron deficiencies when growing in soils having such high pH values, it may be possible that iron is taken up by plants through exchange phenomena or complex formation. Evidence for the importance of some contact effects between roots and iron compounds has been demonstrated by Eaton (3) and subsequently confirmed by others (2, 5, 17). The present paper deals with a comparison between the thermodynamically possible saturation concentration and the minimum required concentration of iron ions in nutrient solutions. In this study inorganic compounds of iron and iron ethylenediaminetetraacetate (FeEDTA) have been used.

The micronutrient cations iron, manganese, zinc, and copper: their uptake by plants from the adsorbed state

Citations

Zinc Deficiency and its Control

Forms, Reactions, and Availability of Nickel in Soils

Soil Manganese in Relation to Plant Growth

The Ionic Composition of some Bog and Fen Waters in the English Lake District

Some quantitative considerations in iron nutrition of higher plants.

Related Papers (5)

The iron-manganese relation in plant metabolism.

Influence of Phosphorus on Zinc, Iron, Manganese, and Copper Uptake by Plants

Plant Uptake of ZINC65 from Soils and Fertilizers in the Greenhouse

Zinc as a Nutrient in Plant Growth

Testing soils for copper, iron, manganese, and zinc.