Polymorphisms of Phosphate Acquisition Parameters in Barley (Hordeum vulgare) Landraces: Secreted Acid Phosphatase and Milieu Acidification of Roots after GerminationIn Vitro

Abstract

Significant differences are shown both for acid phosphatase activities and acidification of phosphorus-deficient germination media, in which 39 genotypes of barley, comprising 34 Finnish landrace and five ‘global’ lines, were grown axenically for 7 days. The differences between barleys had statistical significances varying from p = 0.072 to 3 × 10⁻⁴. Mean acid phosphatase activities varied from 548 to 4525 nMol p-nitrophenol phosphate mg protein⁻¹ h⁻¹. Mean increases in H⁺ concentration during the 7 days varied from 0.7 to 71.6 μMol ml⁻¹ of medium. Acid phosphatase activity highly significantly correlated with the protein amount secreted in the medium (r_s varying in different items between 0.326 and 0.944). Grain mass did not correlate with either acidification (r_s = −0.041) or acid phosphatase activity in the medium (r_s = −0.086). Correlations between acidification and acid phosphatase activity varied, being significant in the total landrace sample (r_s = 0.392), but non-significant in the sample of 27 lines from a landrace population (r_s = 0.068) and in the sample of the global lines (r_s =—0,315). The Finnish landraces were genotype mixtures. Different genotypes could also interact by their roots. Genetic variation was adaptive due to the highly heterogeneous soil microsites and other selective factors that also varied temporally and seasonally, especially during the past field management practices. Complementation in phosphate acquisition between different genotypes in soil was apparent in the genotype mixtures: some landrace genotypes acidified the root environment, while some secreted a high phosphatase activity as shown here, hence also being wide genetic resources of these characteristics. In low-input or organic farming, cultivation of a suitable mixtures of genotypes or cultivars, some with high secreted acid phosphatase activity, the others efficiently acidifying the root environment, might benefit plant nutrition from the sparingly soluble phosphate.