Morphological, Histological and Lipid Changes during Adventitious Budding inPinus pinaster Cultured Cotyledons

Tranvan, H., Troton, D. and Calvayrac, R. 1988. Morphological,histological and lipid changes during adventitious budding inPinus pinaster cultured cotyledons.—J. exp. Bot. 39: 907–915. Isolated cotyledons of Pinus pinaster were cultured under bud-formingconditions. The morphology, histology, lipid content and thechlorophyll pools of the cotyledons were followed during buddevelopment. Comparison with cotyledons cultured continuouslyon hormone-free or hormone-supplemented medium was performed.Three periods were distinguished during bud formation: (i) theinitiation period, characterized by a drastic decrease of triacylglycerols,enhanced by the presence of the hormones; (ii) the differentiationperiod, during which the intense cell divisions and the increaseof the polar lipid and chlorophyll contents appeared stronglycorrelated and (iii) bud development, characterized by stablelevels of both chlorophylls and neutral lipids. Moreover, itappeared that the continuous presence of hormones in the culturemedium inhibited the synthesis of molecular components, in particularchlorophylls and membrane lipids, required for normal cell differentiationand physiology. Key words: Adventitious bud formation, chlorophyll, neutral lipids, Pinus pinaster, cotyledons.