Variation in root hairs of barley cultivars doubled soil phosphorus uptake

Length and density (number mm-1 root) of root hairs of two barley (Hordeum vulgare L.) cultivars Salka and Zita and their capability to absorb phosphorus (P) from nutrient solution as well as from rhizosphere soil were studied. The cultivars were chosen because they differed most among 30 cultivars in ability to absorb P from low P soil in two field conditions. In nutrient solution culture, Salka had 32±4 root hairs mm-1 root, 1.02±0.22 mm long. Zita had 21±3 hairs mm-1 root, 0.54±0.14 mm long. In soil, the root hairs of both the cultivars were slightly longer (Salka 1.10 ±0.16 mm; Zita 0.63±0.18 mm) than in solution culture but the difference was non-significant (p<0.05). The root hairs increased the effective root surface area of Salka by 206% and that of Zita by 81%. In solution culture, Salka produced 163±9 m g-1 and Zita 153±11 m g-1 dry roots in 21 days. Salka produced 1.65±0.22 g and Zita 1.51±0.31 g of green dry matter (DM). The cultivars did not differ in uptake of P from nutrient solution culture. The P content of DM was 0.42±0.1% in Salka and 0.41±0.08% in Zita. In soil, Salka depleted two times more P from rhizosphere than Zita. The longer root hairs of Salka increased the extension of the depletion zone for NaHCO3-Pi (inorganic P extracted with 0.5 M NaHCO3) in the rhizosphere. The cultivars also depleted NaOH-Pi (inorganic P extracted with 0.1 M NaOH) from the rhizosphere soil, but the difference between the cultivars was non-significant (p<0.05). The results suggested that the ability of Salka to absorb more inorganic soil P was due to its longer and denser root hairs.