Somatic embryogenesis in saffron (Crocus sativus L.). Histological differentiation and implication of some components of the antioxidant enzymatic system

Abstract

The ontogenetic developmental stages of saffron somatic embryogenesis have been studied and characterized using light microscopy and the biochemical determination of the antioxidant enzymatic system. The embryogenic callus underwent internal segmented divisions with the formation of globular embryos that were attached to the callus surface by a broad multicellular structure. Further development of the embryoids was characterized by the emergence of a shoot apical meristem and cotyledon (monopolar stage) with the subsequent differentiation of a minicorm at the basal part of the somatic embryo (dipolar stage). During the morphological differentiation of the somatic embryos changes in the antioxidant enzymatic system with increased superoxide dismutase (SOD) and catalase (CAT) activities were detected at the initial stages of somatic embryogenesis. The isoforms of SOD, including two Mn-SODs and four Cu, Zn-SODs, were also detected. Although all the isoforms were expressed during the successive stages of somatic embryogenesis, an increase in Mn-SODs and a decrease in Cu, Zn-SODs during the last two stages was observed. Significant changes were also detected in the antioxidant activities ascorbate peroxidase, dehydroascorbic acid reductase and glutathione reductase.