Excess manganese accumulates in the vacuoles of potato leaves.

Hydrogen-1 nuclear magnetic resonance was used to study potato leaves (Solanum tuberosum L. cv. Norland) grown at low, medium, and toxic levels of manganese. Spin-lattice relaxation data were used to estimate the fraction of total leaf water in the vacuole and the concentration of Mn in the vacuole. The highest vacuolar water fractions (87% of total leaf water) were found in the oldest leaves. In the youngest leaves sampled, the vacuoles contained 30% of total leaf water. Results indicated that excess manganese accumulated primarily in the vacuole and that little or none of it precipitated. The concentration of dissolved Mn outside the vacuole remained low and relatively constant as the Mn content of the vacuoles increased. Vacuolar manganese concentrations as high as 0.02 M were measured.