Phosphate transport in potato cuttings: Effect of gibberellic acid and abscisic acid

Apical cuttings of Solanum tuberosum L. cv. Sirtema were used al different stages of development to study long-distance transport of phosphate. The effects of two hormones, gibberellic acid (GA₃) and abscisic acid (ABA), on this process were also investigated. Before tuberization, phosphate (³²P) supplied to a single leaf was transported preferentially in the young and growing parts of the plant: apical bud, young leaves and roots. After tuberization, the tuber became the principal site of phosphate accumulation. GA³ treatment (10⁻⁴ M) of the tuber as well as of the leaves led to reduced transport of ³²P into the tuber. By contrast, treatment of the tuber with ABA (10⁻⁴M) did not change the ³²P distribution within the plant, while foliar spray with ABA greatly increased the transport into the tuber. The opposite effects of the two hormones on phosphate accumulation by tubers are discussed with regard to their opposite effects on the tuberization process.