Effects of selected trace elements on plant growth

Abstract

Truce elemerits in plurits Lire : tittrniunz, uaiiutlium, cobult, nickel, uluniiiiiutiz, silicoti, ursenic, seletiium, Juoritie und INTROD UCTlONIt is known that living organisms require only small amounts of some elements as nutrients. The effects they produce must be very important, since they appear to participate in key biocatalytic events. The essentiality of an element is established when specific and direct beneficial effects on aspects of growth or metabolism are found, normally by growing agronomic species in purified cultures in which this element was previously added; the omission of the element causes a directly In agricultural ecosystems plants play an important role in the cycling of trace elements, but the role of these trace elements in plant growth is mostly unknown (Aller and Bernal 1986). Although some processes can be activated by a certain number of these trace elements, new research is also necessary in order to determine their biochemical functions in higher plants and establish their general essentiality. Some of these elements (titanium, vanadium, cobalt, nickel, aluminium, silicon, arsenic, selenium, fluorine and iodine) are reviewed in this paper.The elements considered here are known to have beneficial effects on some groups or species but their general essentiality requires confirmation. Interest in these trace elements, which are usually present in plants in small quantities, arises for different reasons. They stimulate plant growth when they are present at small concentrations, although not necessarily under all conditions. Some of them are essential elements for animal nutrition and may be present in amounts large enough to limit the agricultural usefulness of some areas. The content of some elements, such as aluminium, titanium and silicon, in agricultural soils are usually sufficient Aller and Deban 1989); however, we refer to them in the text as trace elements since these elements are used by plants in small quantities for their nutrition.Ingestion of plant foodstuffs is the primary route of entry of trace elements into humans. In turn, the life of man largely depends on the quantity and quality of his food. However, the ability of plants to accumulate trace elements is certainly limited, being affected by several factors such as plant species, plant parts and age, soil and climatic conditions etc. Consequently, research in the field of micronutrients focuses usually on their uptake mechanisms, distribution pathway in the plant, biochemical functions, and deficiency and toxicity levels and states. These are therefore the items covered in this survey. TITANIUM Absorption, transport and accumulationThe aqueous solution chemistry of elements is very complex because of the number of different oxidation states and the formation of oxyions, hydroxyl and probably also organic complexes in different pH regions. Under certain conditions the dissolved species may be in equilibrium with solids. We therefore consider that a convenient way to summarise the chemistry of such a s...

Remedial investigation/feasibility study of the Clinch River/Poplar Creek Operable Unit. Volume 3. Risk assessment information. Appendixes E, F

“…In experiments with toxic levels of arsenic, rice and F1-6 legumes appear to be more sensitive than other plants. Symptoms include wilting of new-cycle leaves, followed by retardation of root and top growth, and leaf necrosis (Aller et al 1990). Arsenic is chemically similar to P, it is translocated in the plant in a similar manner and is able to replace P in many cell reactions.…”

“…Nickel is not generally considered to be an essential element for plants. However, it may be required by nodulated legumes for internal N transport as part of the urease enzyme (Aller et al 1990). It is generally adsorbed as the Ni(II) ion and translocated in xylem and phloem w i t h an organic chelate (Hutchinson 198 A limited number of studies have evaluated the effects of Ni on oak, rye grass, corn, cotton, and beans.…”

Toxicological Benchmarks for Screening Potential Contaminants of Concern for Effects on Terrestrial Plants

“…In experiments with toxic levels of As, rice and legumes appear to be more sensitive than other plants. Symptoms include wilting of new-cycle leaves, followed by retardation of root and top growth, and leaf necrosis (Aller et al 1990). Because As is chemically similar to P, it is translocated in the plant in a similar manner and is able to replace P in many cell reactions.…”

“…Toxicity symptoms due to excess Co are typical of Fe deficiency induced 3-15 chlorosis and necrosis, and root tip damage ). There appears to be inhibition of mitosis and chromosome damage (Aller et al 1990). …”

“…However, it may be required by nodulated legumes for internal N transport as part of the urease enzyme (Aller et al 1990). It is generally adsorbed as the Ni(II) ion and translocated in xylem and phloem with an organic chelate (Hutchinson 1981).…”