Response of lupin cultivars to concentration of calcium and activity of aluminum in dilute nutrient solutions

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Abstract
Although lupins (Lupinus angustifolius L.) are usually grown in slightly acidic soils covering the pH range 6.0 to 6.5, the response of lupin cultivars to a range of acid soil infertility factors has not been investigated. Effects of external Ca concentrations of 150 or 1000 μM and S activities of monomeric Al species (Al reactive with aluminon in 30 min, without acidification and heating; SaA1 mono) up to 80 μM on early growth and mineral composition in tops of three lupin cultivars (Unicrop, Uniharvest, and Uniwhite) were investigated in continuously flowing nutrient solution at pH 4.3 ± 0.1. The dry weight of tops of the three cultivars was generally similar in Uniwhite and Unicrop, and considerably lover in Uniharvest. The weight of tops increased by 24 to 39% while that of roots increased by 11 to 14% with an increase in Ca concentration from 150 to 1000 μM in Al‐free solutions. At each Ca concentration, an increase in activity of monomeric Al resulted in a linear decrease in dry weight of tops (r2 = 0.516 to 0.961). The effect of Al on root weight vas significant only in Uniwhite at both Ca concentrations and in Uniharvest at 150 μM Ca. The SaAl mono associated with a 10% decrease in dry weight of tops were 19, 22, and 24 μM at 150 μM Ca and 19, 18, and 20 μH at 1000 μM Ca for Uniwhite, Unicrop, and Uniharvest, respectively. The Al concentration in tops increased with an increase in SaAl mono in solution at both 150 and 1000 μM Ca and vas higher in plants grown at 150 μM Ca than at 1000 μM Ca. Significant negative correlations were found between the SaA1 mono in solution or concentration of Al in tops and the concentrations of N, P, Ca, Mg, Mn, Cu, and Zn in the tops of the three cultivars.