Root-released organic acids and phosphorus uptake of two barley cultivars in laboratory and field experiments

• Published in: European journal of agronomy 2000-06, Vol.12 (3), p.281-289
• Main Authors: Gahoonia, Tara S, Asmar, Farouq, Giese, Henriette, Gissel-Nielsen, Gunnar, Erik Nielsen, Niels
• Format: Article
• Language: English
• Subjects: Adaptation to environment and cultivation conditions; Agronomy. Soil science and plant productions; Barley genotypes; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Genetics and breeding of economic plants; Nitrogen, phosphorus, potassium fertilizations; Organic acids; Phosphorus efficiency; Phosphorus fertilization; Rhizosphere; Root exudation; Root hairs; Soil-plant relationships. Soil fertility. Fertilization. Amendments; Varietal selection. Specialized plant breeding, plant breeding aims
• ISSN: 1161-0301; 1873-7331
• DOI: 10.1016/S1161-0301(00)00052-6

A major portion of phosphorus (P) applied as fertilizers is bound in soils as P compounds of variable adsorption strength, reducing the effectiveness of P fertilization. Plant genotypes equipped with mechanisms for utilizing the adsorbed P more efficiently can, therefore, enhance the effectiveness of P fertilization. Such genotypes will also enrich plant gene pools for further analysis and upgrading of P efficiency by selection and breeding. We studied the variation and the mechanisms of P uptake of two winter barley ( Hordeum vulgare L.) cultivars Marinka and Sonate (parents of existing 200 haploid progeny lines), by laboratory and field experiments. After cultivation in nutrient solution for 21 days, Marinka produced more roots than Sonate, but similar amounts of dry shoots of lower P content (Marinka 3.4±0.4 mg g −1, Sonate 4.9±0.6 mg g −1). The total P uptake per plant did not differ between the cultivars. Marinka retained more P in roots as indicated by the higher concentration of P in the roots (Marinka 3.9±0.3 mg g −1 and Sonate 3.0±0.4 mg g −1). In sterile nutrient solution culture, the cultivars differed mainly in release of organic acids from the roots, with Marinka releasing three times more citric acid and nearly two times more acetic acid than Sonate. The cultivars had similar root hair lengths and they did not differ ( P>0.05) in depletion of available soil P fraction (extracted with 0.5 M NaHCO 3) in the rhizosphere. Marinka absorbed nearly twice as much P from the strongly adsorbed soil P fraction (extracted with 0.1M NaOH). Also under field conditions, Marinka absorbed more P and produced more shoot dry matter. The higher P uptake by Marinka than Sonate can be attributed to its ability to acquire P from strongly adsorbed soil P by releasing more organic acids, especially citric acid, from its roots.