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Effects of Phosphorus/Aluminum Molar Ratio and Calcium Concentration on Plant Response to Aluminum Toxicity
Author(s) -
Alva A. K.,
Edwards D. G.,
Asher C. J.,
Blamey F. P. C.
Publication year - 1986
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1986.03615995005000010026x
Subject(s) - elongation , chemistry , monomer , calcium , molar concentration , sunflower , phosphorus , nuclear chemistry , helianthus annuus , horticulture , polymer , materials science , biology , ultimate tensile strength , organic chemistry , metallurgy
Abstract Total aluminum (Al) in solution often comprises both monomeric and polymeric Al species. Concentrations of total and monomeric Al and Σ activities of monomeric Al species (Σ a Al mono ) were determined in nutrient solutions at 40 µ M Al with varying P/Al molar ratios (0, 0.02, 0.2, 2.0 and 4.0) and calcium (Ca) concentrations (0.5, 1.5, 5.0, 15 m M ). Effects of these treatments on root elongation of soybean [ Glycine max (L.) Merr.], sunflower ( Helianthus annuus L.), subterranean clover ( Trifolium subterraneum L.), and alfalfa ( Medicago sativa L.) were determined. Concentrations of total and monomeric Al in solution decreased with increasing P/Al molar ratio. Ca concentration had no significant effect on concentration of total or monomeric Al, but significantly affected the Σ a Al mono in solution. Root elongation of the plant species increased with increasing P/Al molar ratio and Ca concentration. The increase in root elongation with increase in P/Al molar ratio was associated with a decrease in monomeric Al in solution. The beneficial effect of Ca on root elongation was evident even when Al in the root environment was expressed as Σ a Al mono , which effectively removes the ionic strength effect of Ca. However, at Σ a Al mono ≥ 18 µ M , increasing Ca concentration failed to improve root elongation. The range of critical Al values for a 50% reduction in root elongation with varying Ca concentration was much narrower if based on Σ a Al mono than on the concentration of monomeric Al in solution. The critical Σ a Al mono , with increasing Ca concentration from 0.5 to 15 m M , varied from 12 to 17 µ M for soybean, <8 to 16 µ M for sunflower, <7 to 15 µ M for subterranean clover, and <5 to 10 µ M for alfalfa.