POLYAMINE CHANGES DURING THE DEVELOPMENT OF ZYGOTIC EMBRYOS IN PRUNUS-AVIUM - EFFECTS OF A 2,4-D AND KINETIN TREATMENT ON GROWTH AND POLYAMINE LEVELS IN COTYLEDONS CULTIVATED IN-VITRO

A study of the polyamine profile was carried out during zygotic embryo development in Prunus avium. Zygotic embryos were collected from 2 do nor trees and sorted into 3 size classes: C1 [2.5 to 3.5 mm]; C2 [3.6 to 4.5 mm] and C3 [5.5 to 7 mm]. Evolution of the various polyamines w as similar for the two donor trees. Changes in the relative amount of the various free polyamines were observed during zygotic embryo develo pment. Agmatine and spermine levels increased from C1 to C3. Spermidin e, the predominant polyamine, showed a two-fold decrease in C3 compare d with C1 and C2; the evolution of putrescine was opposed, showing an increase in the last developmental stage. The putrescine/spermidine ra tio could be a marker for these 3 developmental stages with a higher r atio in C3 compared with C1 and C2. Polyamine changes in cotyledons fr om class C1 were investigated during in vitro culture. A 10-day induct ion on a medium containing 2,4-dichlorophenoxyacetic acid (2,4-D) and kinetin caused a strong decline in free spermidine levels and a dramat ic increase in free putrescine. The formation of conjugated putrescine occurred simultaneously, and twenty days after removal of growth regu lators, the various polyamine contents were still at the same level.