Root, Shoot and Nutrient Acquisition Responses of Mycorrhizal and Nonmycorrhizal Wheat to Phosphorus Application to Highly Calcareous Soils

摘要

Greenhouse pot experiment was conducted to evaluate the response of wheat grown in calcareous soil to arbuscular mycorrhizal fungi (AMF) and P application. The treatments consisted of two factors, five rates of P application (0, 50, 100, 200, 400 kg P ha^-1) and two levels of AMF inoculation (inoculated and non inoculated). Wheat was grown for 7 weeks and at harvest wheat dry matter (DM), P and micronutrients uptake were determined. Roots were extracted and root length and surface area were measured. Roots also were stained in trypan blue and mycorrhizal colonization was determined. AMF inoculation increased mycorrhizal colonization which decreased at higher rates of P levels. Maintaining the maximum DM while the AMF colonization was depressed at higher P rate indicates that the increase in DM was solely due to P. AMF inoculation decreased root length and surface area at higher rates of P. Phosphorus uptake was higher for mycorrhizal plants at 50 and 100 kg ha^-1 P rates only. Linear and quadratic relationship between P uptake and the root surface area were observed for nonmycorrhizal and mycorrhizal wheat, respectively. Higher specific P uptake and higher physiological and agronomical use efficiencies at lower P rates by mycorrhizal wheat suggests that they are more efficient in P absorption and utilization of soil P that is unavailable to nonmycorrhizal wheat. AMF enhanced Fe, Zn and Cu uptake except at high P rates where both mycorrhizal and nonmycorrhizal wheat had similar values of copper uptake.