Gradients in Mn accumulation and changes in plant form for potato plants affected by Mn toxicity.

The time-dependence of Mn accumulation was confirmed in potato foliage (Solanum tuberosum. L.cv. Norland) grown in solution culture. Older leaves grown at 0.61 mM Mn had substantially higher Mn concentrations than younger leaves and stem samples. Levels of Mn in older leaves increased steadily from 4000 µg g−1 at one week to 8–10,000 µg g−1 at 6 weeks, but were relatively constant in the emerging leaves. Even foliage grown at low Mn levels (0.01 mM Mn) had 4 fold gradients in Mn concentration from younger (40 µg g−1) to older leaves (180 µg g−1).