Iron nutrition of Nicotiana tabacum L. in relation to multiplication of tobacco mosaic virus

Tobacco grown in water culture solutions containing various levels of iron responded with a gradient of growth and characteristic deficiency symptoms. Infection with tobacco mosaic virus resulted in decreased growth at all levels of iron. Mosaic symptoms were reduced in intensity by decreased levels of iron. Virus infection of deficient plants reduced the deficiency chlorosis of apical leaves. This reduction of deficiency chlorosis in apical leaves is believed due to translocation of chloroplast components from the basal leaves, released as a result of chloroplast disintegration by virus infection. Moderate iron deficiency did not influence the concentration of virus obtained from leaf samples or leaf discs. Extreme iron deficiency did, however, reduce virus concentration. Only at a low critical level did deficiency of iron exert a greater limitation on virus multiplication than on host growth. At this level, host metabolism was so unbalanced that roots excreted large amounts of a yellow pigment which had properties of riboflavin.