Mechanism of the inhibition of absorption and translocation of phosphorus by aluminum in crop plants

Research Project

Project/Area Number	60470122
Research Category	Grant-in-Aid for General Scientific Research (B)
Allocation Type	Single-year Grants
Research Field	土壌・肥料
Research Institution	Hokkaido University
Principal Investigator	TADANO Toshiaki Faculty of Agriculture, Hokkaido University; Assoc. Professor, 農学部, 助教授 (40001440)
Project Period (FY)	1985 – 1986
Project Status	Completed (Fiscal Year 1986)
Budget Amount *help	¥2,700,000 (Direct Cost: ¥2,700,000) Fiscal Year 1986: ¥600,000 (Direct Cost: ¥600,000) Fiscal Year 1985: ¥2,100,000 (Direct Cost: ¥2,100,000)
Keywords	Aluminum tolerance / Root elongation / Absorption and translocation of phosphorus / アルミニウムと燐の共沈
Research Abstract	1. In the case of barley which is weak in the aluminum tolerance, (1) the root elongation is retarded by aluminum remarkably regardless of phosphorus status of growth media, (2) the phosphorus absorption rate per unit root length is not decreased by 2 ppm Al when the phosphorus level in the growth medium is high, but (3) the rate is decreased by 2 ppm Al when the phosphorus level is low. 2. Co-precipitation of phosphorus and aluminum on the roots decreses the translocation of phosphorus to the shoot irrespective of aluminum tolerance of crop plants. But, degree of the decrease is small. 3. As a result, in the case of crop plants weak in the aluminum tolerance, phosphorus deficiency is promoted strongly by aluminum under conditions of which phosphorus level is lower than 0.05 ppm P, and both aluminum toxicity and phosphorus deficiency become growth limiting factors at the same time. 4. In the case of rice plant which is strong in the aluminum tolerance, co-precipitation of phosphorus and aluminum on the root surface becomes only factor to decrease absorption and translocation of phosphorus by aluminum. Thus, inhibiting effect of aluminum on the absorption and the translocation of phosphorus is very small. 5. Phosphorus contents in the shoot of wheat varieties weak in the aluminum tolerance are lower than those strong in the aluminum tolerance when aluminum level in the growth medium is 10 ppm Al. As factors to decrease phosphorus contents in the shoot, retardation of root elongation by aluminum ehich induce the decrease of phosphorus absorption rate per plant is the most important, followed by the decrease of phosphorus absorption per unit root length by aluminum and the co-precipitation of phosphorus and aluminum on the roots.