The Zn–P interaction was also studied in solution
culture with varied Zn and P supply. In the low-Zn
treatment, the plants appeared smaller at higher P levels
and showed more severe leaf symptoms including chlorosis
and necrosis (Fig. 3). The medium P level increased
the shoot dry weight of the low-Zn plants when
compared to the low P level, but a further increase in P supply tended to decrease the dry shoot biomass
(Table 4). In contrast, at the medium and high Zn levels,
the plants produced significantly more shoot biomass
with the medium or high P supply than with the low P
supply (Fig. 3; Table 4). In terms of root dry weight,
both lower Zn and lower P supplies were associated
with higher values. Consequently, the root-to-shoot ratio
increased dramatically with decreasing Zn and/or P
availability. The root-to-shoot ratio of the low-Zn-low-
P plants was over three times as high as that of the high-
Zn-high-P plants.