‘Red Prince Delicious’ apples/‘M7’ rootstocks, growing in sand culture and receiving ½, 5 or 50 ppm Mn, developed internal bark necrosis (IBN), and an Fe-deficiency chlorosis in its severest expression, at the highest level of Mn supply. Fe was as high in leaves of chlorotic as in those of non-chlorotic plants, but the chlorosis was cleared up by increasing the Fe supply.
Ground twigs showed a brownish coloration which had a max reflectance at 700 mμ. Differences in coloration were correlated with the Mn supply, the severity of IBN symptoms and the Mn/Fe ratio in the leaves and bark, but not with the Mn/Fe ratio in the ground twigs.
Received for publication June 2, 1972. Contribution from the Departments of Horticultural Science and Soil Science. Published with the approval of the Director of Research as Paper No. 3774 of the Journal Series.
Associate Professor of Horticultural Science and Assistant Professor of Soil Science, respectively, Mountain Horticulture Crops Research Station, Fletcher, N. C.