Apical and Distal Pieces of Aged Potato Tubers Respond Differently to Paclobutrazol

Abstract

The influence of paclobutrazol, an inhibitor of GA synthesis, on kindertuber formation was studied using 13.5-month-old `Russet Burbank' potato (Solanum tuberosum) tubers. Suberized apical and distal tuber pieces of equal weight were sprayed daily with distilled water (control), 0.001 and 0.01 mg paclobutrazol/liter with or without 2.5 mg kinetin/liter, and 2.5 mg kinetin/liter alone. The tuber pieces were held in the dark (20C) and harvested 8, 16, and 22 days after the first treatment. Only sprouts developed from control apical piece eyes after 22 days. There was an average of 3.6 sprouts/eye, which, in total, weighed 735 mg. Sprouts (2.4/eye) from treated apical piece eyes averaged 46 mg. By 22 days, 0.001 mg paclobutrazol/liter plus kinetin applied to apical pieces resulted in the most kindertubers, 1.9/eye. The largest kindertubers (1.2 g) were produced from apical pieces treated with 0.001 mg paclobutrazol/liter. At each harvest and regardless of treatment, distal tuber pieces produced larger sprouts and more sprouts per eye than apical pieces. Kindertubers developed from distal piece eyes only with the paclobutrazol plus kinetin treatments. Distal eyes produced half as many kindertubers as apical eyes treated similarly. Apical pieces treated with kinetin alone produced fewer sprouts than control pieces, and fewer tubers than paclobutrazol-treated pieces. Sprout weight per eye of kinetin-treated apical pieces was one-third that produced by control pieces and 5.1-fold greater than that of paclobutrazol-treated pieces. A similar trend was observed with sprout weight from distal eyes. Results suggest lowered GA levels are involved in kindertuber formation on aged potato tubers, and GA content or metabolism of distal pieces is unlike that of apical pieces. Distal tuber pieces do not form kindertubers as readily as apical pieces.