Control of tuberisation in potato by gibberellins and phytochrome B

Phytochrome B-deficient plants exhibit increased gibberellin (GA) levels or responsiveness, which may contribute to their elongated growth and reduced chlorophyll levels. We have investigated the effects of applications of gibberellic acid and an inhibitor of gibberellin biosynthesis, ancymidol, on wild-type and phytochrome B-antisense potato (Solanum tuberosum ssp. andigena) plants. The results showed that some phenotypes of the phytochrome B-antisense plants, i.e. increased stem length and reduced chlorophyll, can be mimicked by treating wild-type plants with gibberellic acid. However, another phenotype, i.e. tuberisation response in long days, is mimicked by application of a GA biosynthesis inhibitor ancymidol, thus appearing to be the result of a reduction in the gibberellin levels. A simple increase in gibberellin levels or sensitivity is, therefore, not sufficient to explain the phenotype of the antisense plants.