Root Organic Acid Exudation As A Physiological Cause For Soil Phosphorus Deficiency Tolerance In Vigna Unguiculata (L.) Walp (Cowpea) Lines

Abstract

Phosphorus (P) fertilizers are not readily available in underdeveloped countries, and excessive P application can lead to problems such as eutrophication. The nonrenewable nature of P mined for use in fertilizers raises concerns that P fertilizers may become more expensive and less accessible. The objective of this study was to measure root organic exudation in Vigna unguiculata (L.) Walp. (cowpea) in response to soil P deficiency. Eight cowpea lines were planted in coarse silica sand and given three treatments: a nutrient solution with P, a nutrient solution without P, and a nutrient solution without P but with rock phosphate included in the sand. It is suspected that organic acid exudation will increase in plants treated with solutions without P. Six organic acids were identified in the root exudates samples, but no difference was observed in the type of organic acids exuded among different cowpea lines. Succinic acid and maleic acid were identified as the two most likely candidates for exudation as a physiological response to low soil P conditions. Lines that have been found to exhibit increased soil P deficiency tolerance could be exuding larger quantities of these organic acids than lines that exhibit low or moderate soil P deficiency tolerance.