Gibberellic acid and the inhibition of aerial tuberisation in Solanum tuberosum L.

The sensitivity of aerial and subterranean tuberisation to photoperiod was studied in potato (Solanum tuberosum cv. Aracy). Although photoperiodic sensitivity varied with the position along the stem, all buds could be induced to develop tubers under SD. Gibberellic acid (GA₃) applied to induced (30 short days) cuttings inhibited the photoperiodic effect. No tubers were formed and orthotropic shoots developed instead. The GA₃ caused a reduction in starch content in induced buds, lowering it to the same level as found in long-day treated plants. However, -amylase activity of buds of induced plants was not affected by GA₃, suggesting that GA₃ does not inhibit tuberisation by promotion of starch hydrolysis.