Comparative uptake kinetics and transport of cadmium and phosphate inPhleum pratense‐Glomus deserticolumassociations

摘要

AbstractMycorrhizal plants (timothy grass,Phleum pratensewithGlomus deserticolum) were compared to nonmycorrhizal timothy grass to determine the effect of the mycorrhizal condition on the uptake and transport of cadmium. Companion experiments were conducted to ascertain phosphate uptake kinetics of mycorrhizal and nonmycorrhizal plants. Divalent cation competition experiments also were employed in this study. Comparisons of the high‐affinity uptake mechanisms between mycorrhizal and nonmycorrhizal plants identified higher levels of phosphate uptake were due to an increase in the number of uptake sites rather than to differences in affinity. The respective values forKmfor high‐affinity phosphate uptake were 2.5 ± 1.3 μM P (mycorrhizal) and 3.4 ± 1.3 μM P (non‐mycorrhizal), but these values were not statistically different at the α = 0.05 level. High‐affinity Cd2+uptake differed significantly between mycorrhizal (4.5 ± 2.8 μM) and nonmycorrhizal (2.8 ± 1.1 μM) plants. Presence of Ca2+at 1.0 mM concentration conferred considerable competitive protection in both the mycorrhizal and the nonmycorrhizal conditions. The effect of Ca2+was an approximate fourfold increase in the re