ダイズ根圏におけるAlの挙動に対する養分吸収の影響

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The effects of nutrient uptake by plant roots on the solubility of Al in volcanic ash soil were studied. The soil used was classified as Alic Meranudand, which contains a large amount of active Al. Soybean plants were grown in a greenhouse for 84 d. The concentrations of K, Ca, Mg, Na and Al in plants and in soil solutions at different growth periods were measured. The mass flow of the elements from soil solution to the root surface was calculated from the concentrations in the soil solution and the daily transpiration of soybean. The concentrations of nutrient cations (Ca^<2+>, K^+ and Mg^<2+>) in the soil solution decreased as the soybean plants grew. On the other hand, the concentrations of Al^<3+> increased; the value of 10μmol(+) L^<-1> in the vegetative growth stage increased to 25μmol(+) L^<-1> in the podding stage. The concentrations of Al^<3+> negatively correlated with the concentrations of nutrient cations (i.e. Ca^<2+> and K^+). For soil solutions collected from unplanted pots, no correlations between the concentrations of Al and the concentrations of nutrient cations were observed. It was assumed that soybean roots released H^+ with the uptake of nutrient cations, and the H^+ caused the pH decrease near the roots, thus, the Al was desorbed from the soil solid phase. Although the pH values of the bulk soil were 6.0-6.2 during the soybean growth, exchangeable Al content increased after cultivation. Although the ratio of mass flow to actual uptake of Al was 1.1 at the vegetative growth stage, it increased to 2.1 at the podding stage. This shows that the mass flow of Al was in excess of what is absorbed by the plants, thus the Al accumulated near the roots at the podding stage. These results provide useful information on the mechanisms of Al toxicity and tolerance in plants.
社団法人日本土壌肥料学会の論文
2005-02-05

ダイズ根圏におけるAlの挙動に対する養分吸収の影響

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