EXPLANATION FOR THE LACK OF DIVISION OF PROTOPLASTS FROM STEMS OF RUBBER-TREE (HEVEA-BRASILIENSIS)

Application of in vitro culture techniques to Hevea brasiliensis has encountered serious difficulties. In particular, protoplasts have been found to be recalcitrant to division. The aim of the present work was to compare biochemically non-mitotic protoplasts isolated from young Hevea stems with mitotic protoplasts from Citrus, tobacco and rice cells. Hevea tissue maceration did not promote ethylene production contrary to the mitotic systems, rather aminocyclopropanecarboxylic acid (ACC) synthesis occurred. Large increases in superoxide dismutase (SOD) and peroxidase (PER) activities during maceration indicated the occurrence of a peroxidative phenomenon. During Hevea protoplast culture, a rapid decrease in viability was associated with an increase in ethylene production, reactions common to stress conditions. Activities of enzymes involved in the production and elimination of toxic oxygen forms were not related to protoplast reactivity. Differences in polyamine content and especially the high putresceine/spermididine + spermine ratio could be used, together with ethylene rise during culture, as markers of Hevea protoplast recalcitrance in culture. Thus, a number of physiological phenomena are associated with lack of mitotic division of stem protoplasts of rubber.