TUBER INDUCTION IN ONE NODAL EXPLANTS SUB MITTED IN-VITRO TO SHORT DAYS ENZYMATIC-ACTIVITY VARIATION EVALUATED WITH 2 MARKERS - SOLUBLE SACCHAROSE AND PEROXYDASE

This work is an attempt to precise the events preceding tuber inductio n of potato plants in vitro submitted to short days, SD. Enzymatic mar kers (saccharose activity, I, and peroxydase activity, Per), measuring metabolic sequences taking place during the process, were used for. F rom the synthesis of our own results and of different authors ones on the subject, it appears that the ''SD effect'' leads, as a metabolic s tress, to a rapid senility state and to the stem growth stopping. The prime causal effect is a photosynthetic production shortage, mainly in saccharose, a high rate of which (beyond the specific or varietal bre ak-even point) being necessary to make firm both the fixation of AlA o n the cell membrane and the ATP reduction. The stress consequence is a n adaptative response of potato plants conducting in three successive stages to the tuber induction. The two first stages of the process are discussed on in this paper.