|Allan, Deborah - UNIVERSITY OF MINNESOTA|
|Johnson, Jane - UNIVERSITY OF MINNESOTA|
|Knight, Diane - UNIVERSITY OF MINNESOTA|
Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: July 15, 1996
Publication Date: N/A
Technical Abstract: Under low P conditions, white lupin responds with a suite of developmental and biochemical changes that result in the exudation of copious amounts of citrate and malate, thereby increasing plant available P. When P is withheld, clustered tertiary meristems on young secondary roots are visible by 6 days after shoot emergence (DAE) and these meristems emerge through the cortex by 9 DAE into proteoid root zones. Within one day of proteoid roots becoming visible, phosphoenolpyruvate carboxylase (PEPC) mRNA expression is enhanced in proteoid roots compared to normal roots. Soon after, amounts of PEPC enzyme and specific activity of PEPC are higher in proteoid compared to normal roots. Carbon fixation by root PEPC contributes approximately 33% of the carbon required for enhanced citrate and malate exudation from the proteoid root zone. Coincident with increases in PEPC activity, extracellular acid phosphatase activity is also oenhanced in proteoid compared to normal roots.