Manganese toxicity as indicated by visible foliar symptoms of Japanese white Tbirch (Betula platyphylla var. japonica)

For the purpose of a field diagnosis of Mn toxicity, we showed the possibility of using isible foliar symptoms of Japanese white birch (Betula platyphylla var. japonica Hara) s indicator. To examine the relationship between the expression of visible symptoms nd leaf Mn concentrations, white birch seedlings were grown under four different Mn evels: 1 mg Mn l-1 as control, 10, 50 and 100 mg Mn l-1. Foliar symptoms of Mn oxicity for white birch were: (1) chlorosis at entire young leaves in the 50 and 100 mg n l-1 treatments; and (2) brown speckles at the leaf marginal and interveinal area for old eaves in the treatments greater than 1 mg Mn l-1. Mn preferably accumulated into the eaf marginal and interveinal area, where the brown speckles were observed. The echanism determining the expression of symptoms seems to be associated with the hysiological state related to leaf age as well as Mn distribution and concentration within leaf.