Effect of Concentration of the Aluminum Ion on Root Development and Establishment of Legume Seedlings

Abstract

Alfalfa, red clover, ladino clover, alsike clover, and birdsfoot trefoil were germinated in soil (pH 6.5) or in inert silica (8 mesh) and allowed to root in a [Formula: see text] Hoagland and Snyder's nutrient solution (pH 4.5) with 0, 0.5, 1, 2, 4, and 10 p.p.m. of added aluminum. Each species, germinated in silica, was also rooted in an unlimed acid soil (pH 4.6) and the same soil limed to a pH of 6.5.Concentration of aluminum ion remaining in solution was 0, 0.1, 0.2, 0.5, 1.0, and 2.0 p.p.m. Saturation extracts of the unlimed and limed soil contained 0.45 and 0.0 p.p.m respectively of aluminum ion in solution. The pH of the nutrient solutions with 0.5, 1, and 2 p.p.m. of added aluminum increased to 5.0 or higher in 24 hours while that with 4 and 10 p.p.m. of added aluminum remained relatively constant.Seedling weight and chemical composition of the tops and root portions varied significantly between species. Alfalfa and red clover showed the most vigorous rate of establishment, and yields were higher with 0.1 and 0.2 p.p.m. concentration of aluminum ion than with the zero treatment. Significant restriction of top and root growth of all species occurred with less than 1.0 p.p.m. of aluminum ion while 2.0 p.p.m. was toxic to root growth. Growth restrictions were more severe at 21 days after seeding than at the 28- or 32-day stages. Yield of tops and roots growing into unlimed acid soil were 73 and 71% respectively of those growing into limed soil. Aluminum taken up by the plant was concentrated in the roots and only with the concentration of aluminum at 2.0 p.p.m. was the content in the tops increased significantly. Phosphorus in the roots, which increased significantly with aluminum ion concentration, was apparently immobilized by aluminum. Percent Ca in the roots increased and in the tops decreased with increasing concentrations of aluminum. Content of K and Mg also varied with aluminum concentration.

Response to soil aluminium of two white clover (Trifolium repens L.) genotypes

“…The increase in aluminium concentration in roots compared to shoots, observed in the experiment, is normal in forage legumes (Haynes and Ludecke, 1981;Macleod and Jackson, 1965;Munns, 1965). The ability of genotype 77 to maintain low aluminium in its roots rather better than genotype 129 did, is a novel result for white clover.…”

Effect of different aluminium and phosphorus levels on aluminium-tolerant and aluminium-susceptible genotypes of white clover (Trifolium repensL.)

“…In the current experiment Al concentrations were again lower in shoots than in roots, which is normal for forage legumes (Macleod & Jackson 1965;Haynes & Ludecke 1981). However, shoot Al concentration was significantly lower, and root Al concentration significantly higher in the tolerant T77 genotype.…”

“…In grasses, root growth may be stimulated more than shoot growth (Hackett 1962). The response offorage legumes to Al has been less researched under strictly controlled conditions, but positive responses to low Al levels occur in data for lucerne and red clover (Macleod & Jackson 1965), lucerne roots (Munns 1965), and white clover (Jarvis & Hatch 1987). The results from solution culture experiments support a possible role for Al as an essential trace elementa view strongly held by Bertrand & Wolf (1966, 1968)-although Bollard (1983) in a review of the evidence considered further research was required.…”

Studies onRhizobiumstrains

“…From the work of Anderson (1956) and Davies (1956) it can be assumed that deficiency of molybdenum could have operated in the above described soil experiment notwithstanding the fact of this element having been applied in fertiliser form as a basal dressing. Toxicity of aluminium (Munns 1965b(Munns , 1965cMacLeod and Jackson 1965) and toxicity of manganese (Vose and Jones 1963) could also have been interacting factors in this kind of study. It is proposed to discuss these and other aspects of the manner in which rhizobia may behave at low levels of pH in a second paper of this series which will deal with the work that is being conducted on Rhizobillm trifolii.…”