PHYSIOLOGICAL TRANSFORMATION OF GROWTH PO TATO TRANSFORMANTS

The incorporation of bacterial genes into the potato genome induces th e formation of phenotypically different transformants that show expres sive growth and metabolic changes. The transformants cv. Zvikov 1361 a re noted for their excessive root formation which is stimuled by the p resence of the plasmid Ri. It is necessary to limit the rhizogenesis i n order to induce transformant tuberization. 2,3,5-triiodobenzoic acid and cumarin in the concentration 2 and 4 mg.1-1 TIBA or 25 and 50 mg. 1-1 cumarin limit the root growth and induce axillary microtubers. Ano ther type has been derived by the transformation of the cv. Oreb with plasmid LDA 1334. This type also brings gene 4 into potatoes and induc es higher synthesis of cytokinins. The transformants were noted for th e formation of multiple shoots which were not able to produce roots an d tubers on media modified by auxin substances. Only transformant graf ting on a tomato has caused elongation and stem rooting in the soil an d also the formation of tubers in flower-pots. The tubers were smaller and had a prolonged shape and contained few starch grains. During the analysis of amino acids it was remarkable to observe two to three tim es lower proline content. The shortage of proline in transformants cou ld result in the lower resistance of transformants under less positive conditions. In the next vegetation period we verified the influence o f exogenously applied proline on transgenic cv. Oreb in leaves that we re growing in an experimental field and in a hotbed. As a result of th e bioassays on coleoptile oat segments, it is evident that proline in leaves lowers the content of auxin substances in most cases and evokes inhibitions. The changes suggest the possible presence of abscisic ac id which could contribute to the regulation of leaf stomata.