Interactive effects of low phosphorus and elevated CO2 on root exudation and nutrient uptake in wheat is modified under sulphur nutrition

Abstract

We investigated the influence of elevated CO2 concentration (e[CO2]) on the interaction of phosphorus (P) and sulphur (S) on nutrient uptake efficiency of wheat. Experiments were conducted on wheat varieties PDW-233 (Triticum durum) and PBW-396 (T. aestivum) under different levels of [CO2] (400 and 700 ppm) with low P (5 µM), low S (10 µM) or low P/S and control (P 500 µM and S 2000 µM). Results revealed an increased biomass accumulation under e[CO2] with low P or S as compared to ambient CO2 concentration (a[CO2]). The root biomass was doubled with higher belowground dry matter partitioning under low nutrient and e[CO2]. Low P and S restricted plant growth directly by reduction in biomass accumulation and limited exudation of total carboxylates from root, however e[CO2] helped to overcome these deficiencies. Interactive effects of e[CO2] and low P or low P/S resulted in increased root length, surface area, volume and number of lateral roots. Under limited P and e[CO2], S provided stability to enzymes involved in root exudation and accelerated mobilization of P and its uptake efficiency. The activity of enzymes viz., phosphoenolpyruvate carboxylase, citrate synthase, malate dehydrogenase and pyruvate kinase, involved in carboxylate synthesis showed significant increase under e[CO2]. Further, the concentration of P and S increased under e[CO2] in shoot and root tissues of both varieties. Under limited P and S supply, e[CO2] helped in modification of root morphology and higher root exudation, which improved nutrient uptake in both varieties.