La biosynthése des stérols dans les tissus de tabac cultivés in vitro

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Abstract
Tobacco tissues grown in vitro were fed with labelled acetic acid during 5, 30 and 150 min, respectively. 4, 4‐Dimethylsterols, 4‐methylsterols and sterols were extracted and purified and their specific activities were determined by acetylation of biosynthetically labelled alcohols with [3H]acetic anhydride of known specific activity.On the basis of the measured specific activities, a tentative scheme for plant sterol biosynthesis is proposed. In particular, cycloartenol appears to play a direct role in this biosynthesis. The conversion of cycloartenol into sterols appears to be a non‐specific process with several possible parallel routes. The linear scheme previously proposed, involving the following transformations : cycloartenol → methylene‐24 cycloartanol → cycloeucalenol → obtusifoliol →“lophenols”, etc., appears to be only one of the pathways followed in our material.