Root excretion of carboxylic acids and protons in phosphorus-deficient plants |
| |
Authors: | Neumann G Römheld V |
| |
Institution: | 1.Institut für Pflanzenern?hrung (330), Universit?t Hohenheim, D-70593, Stuttgart, Germany ; |
| |
Abstract: | Phosphorus deficiency-induced metabolic changes related to exudation of carboxylic acids and protons were compared in roots
of wheat (Triticum aestivum L. cv Haro), tomato (Lycopersicon esculentum L., cv. Moneymaker), chickpea (Cicer arietinum) and
white lupin (Lupinus albus L. cv. Amiga), grown in a hydroponic culture system. P deficiency strongly increased the net release
of protons from roots of tomato, chickpea and white lupin, but only small effects were observed in wheat. Release of protons
coincided with increased exudation of carboxylic acids in roots of chickpea and white lupin, but not in those of tomato and
wheat. P deficiency-induced exudation of carboxylic acids in chickpea and white lupin was associated with a larger increase
of carboxylic acid concentrations in the roots and lower accumulation of carboxylates in the shoot tissue compared to that
in wheat and tomato. - Citric acid was one of the major organic acids accumulated in the roots of all investigated species
in response to P deficiency, and this was associated with increased activity and enzyme protein levels of PEP carboxylase,
which is required for biosynthesis of citrate. Accumulation of citric acid was most pronounced in the roots of P-deficient
white lupin, chickpea and tomato. Increased PEP carboxylase activity in the roots of these plants coincided with decreased
activity of aconitase, which is involved in the breakdown of citric acid in the TCA cycle. In the roots of P-deficient wheat
plants, however, the activities of both PEP carboxylase and aconitase were enhanced, which was associated with little accumulation
of citric acid. The results suggest that P deficiency-induced exudation of carboxylic acids depends on the ability to accumulate
carboxylic acids in the root tissue, which in turn is determined by biosynthesis, degradation and partitioning of carboxylic
acids or related precursors between roots and shoot. In some plant species such as white lupin, there are indications for
a specific transport mechanism (anion channel), involved in root exudation of extraordinary high amounts of citric acid.
This revised version was published online in June 2006 with corrections to the Cover Date. |
| |
Keywords: | Aconitase organic acids phosphoenolpyruvate carboxylase phosphorus deficiency rhizosphere acidification root exudates |
本文献已被 SpringerLink 等数据库收录! |
|