Differential responses of root and root hair traits of spring wheat genotypes to phosphorus deficiency in solution culture

Root plasticity is important for plants to adapt to heterogeneous nutrient environments. The differential responses of six spring wheat genotypes were investigated; the plants had been subjected to deficient (2 μmol) and abundant phosphorus (P) (200 μmol) concentration. Root (length, surface area and diameter) and root hair traits (length and density), soil acidification and uptake of macro- and micronutrients were determined. Under low P supply all genotypes exhibited symptoms of P stress, such as poor shoot and root growth, starch accumulation and a release of substantial quantities of proton and acid from roots. Larger genotypic differences in root hair length and density than root length, surface area and diameter were observed. In response to P stress genotype April Bearded responded strongly by increasing its root hair density, while A35-213 and Hankkijan Tapio substantially increased root hair length. Other genotypes showed less positive responses or even negative ones in root hair traits. Thus, density of root hairs appears to be a more P-regulated and P-responsive trait than root hair length. April Bearded acidified the most and Hindy62 released most organic acid in response to P deficiency.