Chemical Composition of Alfalfa as Related to Degree of Tolerance to Manganese and Aluminium

Abstract

In an attemDt to studv the nature of plant tolerance to soil acidity and related factors,'a series of investigations was conducted with sand cultures to determine the chemical composition of alfalfa as related to its response to various concentrations of manganese, aluminium and calcium' All clones studied were affected, but to a variable degree, by an excess of manganese and aluminium, They absorbed approximately the same amounts of these elements but considerable differences rvere noted in their rate of translocation from the roots to the aerial orsans. As a result, plants *'hich were the least affeeted hv manqanese and aluminium conrained smaller amounts of those trvo eleme-nts iniheir stems and leaves and larger amounts in their roots.Moreover, for a given content of manganese and aluminium in aerial organsi the degree of irrj-ury was approximatcl-y the same lor all clones. More tolal and witer-solubie ialcium'ii'as found in so-called tolerant than non-tolerant olants. Also. an increase in the calcium concentration of the nutrient culture uas effective'in reducine manqanese toxicity. These results suggest the theory that the rate of u"ptal<e of calcium by the plant is one o[ the factors determining it-s degree of tolerance to manganese and alumtnlum.Can. J. Plant Sci. Downloaded from pubs.aic.ca by YALE UNIV on 07/26/15For personal use only.

Toxicity and Tolerance in the Responses of Plants to Metals

“…The best-known accumulator species is undoubtedly tea, in which mature leaves may contain in excess of 20,000 ppm Al (SIVASUBRAMANIAM and TALIBUDEEN 1972), concentrated particularly in thickened epidermal cells (MATSUMOTO et al 1976). (2) Species in which tolerant forms accumulate Al in the roots but do not transport it to the shoot; a response of this type is reported for Azalea (LUNT and KOFRANEK 1970), cranberry (MEDAPPA and DANA 1970), some genotypes of Medicago sativa (OUELLETTE and DESSUREAUX 1958) and triticale and rye (MUGWIRA et al 1976). (3) Species in which Al tolerance is associated with exclusion of the metal; examples include cultivars of wheat and barley (Foy 1974).…”

Trigo: efeito de magnésio combinado com forças iônicas em solução nutritiva na tolerância ao alumínio

“…Os resultados obtidos mostram que, aumentando-se as concentrações de Mg nas soluções, houve uma diminuição nos efeitos tóxicos do alumínio, confirmando OUELLETTE & DESSUREAUX (1958), LUND (1970), CLARKSON & SANDERSON (1971) e ALI (1973. A diminuição da toxicidade de Al 3+ também foi demonstrada pelo aumento, nas soluções, dos níveis de Ca (ALI, 1973, e CA-MARGO, 1985b), de K (AIMI & MURAKAMI, 1964, e ALI, 1973, e de Na (ALI, 1973).…”

“…Segundo vários autores (CLARKSON & SANDERSON, 1971;OUELLETTE & DESSUREAUX, 1958;CAMARGO, 1985b), maior quantidade de cálcio era necessária para manter um crescimento normal das plantas em presença de alumínio. DIOS & BROYER (1962) demonstraram em experimentos com soluções nutritivas contendo 4 a 17 ppm de Al, que, com a adição de níveis elevados de magnésio, houve um pequeno aumento na produção de matéria seca total das plantas de milho em relação às soluções sem alumínio.…”

Efeitos de níveis de cálcio combinados com diferentes concentrações de sais na tolerância de trigo à toxicidade de alumínio, em solução nutritiva

“…Foi ainda tolerante ao Al 3+ quando se acrescentaram 160 e 320 mg/litro de Ca nas soluções de tratamento, independente da concentração salina e do tempo de crescimento. Estes resultados confirmaram que seria necessária maior quantidade de cálcio na presença de Al 3+ para manter o crescimento radicular (OUELLETTE & DESSUREAUX, 1958).…”