Carbohydrate Levels and Photoassimilate Export from Leaves of Phaseolus vulgaris Exposed to Excess Cobalt, Nickel, and Zinc

Exposure of white bean seedlings to phytotoxic burdens of Co, Ni, or Zn reduced the export of ¹⁴C-photoassimilates from the nearly fully expanded unifoliate leaves. Little ¹⁴C reached the major sink areas, the young trifoliate leaves and the root tips, of seedlings exposed to metal. The unifoliate leaves accumulated sucrose, reducing sugars, and starch. These effects were evident within 1 or 2 days.