Effect of Lanthanum on Ion Absorption in Corn Roots 1
AUTOR(ES)
Leonard, Robert T.
RESUMO
Short term (10 min) influx of 86Rb-labeled potassium into corn (Zea mays L. WF9 × M14) root segments was inhibited by La (NO3)3 or LaCl3. Half maximal inhibition of K+ influx from 0.25 mm KCl was obtained with 0.025 mm La3+. Kinetic analysis indicated the inhibition to be of a competitive nature. With absorption periods exceeding one hour, La3+ no longer inhibited, but rather stimulated K+ influx rates. La3+ was not an inhibitor of 36Cl or 32P absorption. Separated cortex and stele absorbed labeled potassium (and phosphate) at comparable rates, and La3+ inhibited potassium influx in both tissues. The effects of La3+ on ion absorption were similar to those of Ca2+, suggesting that the two polyvalent cations act at the same site. Based on this and the observation that La3+ does not seem to penetrate the plasma membrane, it was concluded that La3+ and Ca2+ affect changes in ion transport without entering cells.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=541654Documentos Relacionados
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