Genotypic variations in the adaptive response to low-phosphorus(P) stress and P-uptake efficiency have been widely reported in many crops.We conducted a pot experiment to evaluate the P-acquisition ability of two rapeseed(Brassica napus) genotypes supplied with two sparingly soluble sources of P,Al-P and Fe-P.Then,the root morphology,proton concentrations,and carboxylate content were investigated in a solution experiment to examine the genotypic difference in P-acquisition efficiency.Both genotypes produced greater biomass and accumulated more P when supplied with Al-P than when supplied with Fe-P.The P-efficient genotype 102 showed a significantly greater ability to deplete sparingly soluble P from the rhizosphere soil because of its greater biomass and higher P uptake compared with those of the P-inefficient genotype 105.In the solution experiment,the P-efficient genotype under low-P conditions developed dominant root morphological traits,and it showed more intensive rhizosphere acidification because of greater H+ efflux,higher H+-ATPase activity,and greater exudation of carboxylates than the P-inefficient genotype.Thus,a combination of morphological and physiological mechanisms contributed to the genotypic variation in the utilization of different sparingly soluble P sources in B.napus.
