In roots of 66-day-old wheat plants grown in nonautoclaved
soil, the extent of mycorrhizal colonization depended only on the P supply (Fig. 2). With each
increase in P rate, a dramatic decrease was observed in
the mycorrhizal colonization score under both the low-
Zn and high-Zn conditions. In plants grown in
autoclaved soil, mycorrhizal colonization was not detectable
at booting (data not shown). The shoot Zn
concentration at anthesis was significantly affected by
the triple interaction of the soil sterilization, Zn and P
treatments (Table 2). In non-autoclaved soil, the low-P
plants had markedly higher shoot Zn concentrations
than the medium-P and high-P plants at both Zn supply
levels. This effect of P supply on the shoot Zn concentration
disappeared completely in autoclaved soil where
the shoot Zn concentrations of the high-Zn plants were
4–5 times as high as those of the low-Zn plants irrespective of the P level. In terms of the shoot P
concentration, the interaction of soil sterilization and P
application appeared to have the most important effect.
Higher soil P applications resulted in remarkably higher
shoot P concentrations in any case. Autoclaving the soil
reduced the shoot P concentration by 35 % at the low P
level, but did not have any significant effect on it at the
medium and high P levels.