Differences in invertase activity in embryogenic and non-embryogenic callifrom Medicago arborea

The different invertase activities in embryogenic and non-embryogenic calli induced from explants (cotyledons, petioles, hypocotyls and leaves) obtain ed from Medicago arborea L. subsp. arborea seedlings were evaluated. Total invertase activity was lower in the calli with the greatest embryogenic cap acity. The greatest fraction of this activity corresponded to soluble inver tase. Wall-bound invertase showed maximum activity during the first two mon ths of culture and the highest activities of this type were found in non-em bryogenic calli. Extracellular invertase formed the smallest fraction of th e total invertase activity evaluated. Acid and alkaline invertase activitie s were found in all calli but differences were detected between the embryog enic and non-embryogenic calli. In the former, the activity of both types o f invertase exhibited a similar type of behaviour but different from that o bserved in the non-embryogenic calli. The calli with the greatest embryogen ic capacity had very low levels of acid invertase and very high levels of t he alkaline form. Soluble invertase - both acid and alkaline - accounted fo r the highest fraction after the first two months of culture and was presen t in lower amounts in the embryogenic than in the non-embryogenic calli. Re garding bound invertase, the highest production was seen to correspond to a cid invertase. The extracellular invertase evaluated corresponded to the ac id form since the alkaline extracellular invertase did not show any physiol ogically significant activity.