Mottle-Leaf in Citrus Artificially Produced by Lithium

Abstract

Mottle-leaf of citrus has been produced artificially in sand and soil cultures as well as in the field by the use of lithium. Li is assumed to act as a poison to the growth processes going on within the leaves, so that they are unable to utilize fully the inorganic salts in the tracheal sap, and as a consequence of the effect of the poison on the growth processes the old mottled leaves have the composition of immature normal leaves. Analyses of the sap of comparable portions of mottled ana normal citrus trees in the field have shown that, although the leaves of mottled trees may show a deficiency of Ca, the tracheal sap may contain large concentrations, possibly because of the inability of the mottled leaves to utilize it. Although no Li is at present known to occur in citrus leaves, the success in the artificial production of mottle-leaf by the use of this toxic substance adds to our understanding of the mottle-leaf phenomenon.