Abstract
The effects of manganese and nitrogen levels on the occrrence of so-called“Abnormal defoliation”of Satsuma orange were studied, using young trees in sand culture.
The high levels of manganese in nutrient solution induced the increase of manganese content in fibrous fine roots and in leaves. In this case, the manganese content in leaves increased up to the same level in the trees showing the symptom of“Abnormal defoliation”in orchard, and the brown spots which are characteristic of“Abnormal defoliation”were observed on some leaves of the experimental trees, without accompanying any other injurious effects such as retardation of growth, decay of roots, and as defoliation.
Manganese content in the fibrous roots was increased along with the increase of nitrogen concentration in nutrient solution, whereas the change of manganese content in leaves was not observed.
From the results mentioned above, it was concluded that the excessive absorption of manganese may be due to the excess of available manganese in the culture media, and also that the brown spots appearing in leaves will be taken to be the primary or essential symptom of this disorder.
