Differences in pectic polysaccharides between carrot embryogenic and non-embryogenic calli.

Cell walls and media were obtained from three kinds of carrot cell culture, namely, embryogenic callus (EC), non-embryogenic callus (NC) and somatic embryos (SE), and analyzed for their sugar content and sugar composition by electrophoresis and gas chromatography. EC formed large cell clusters while NC formed small clusters. Observations under the light microscope revealed that the intercellular contacts in NC were much more limited than those in EC. The analysis of pectic polysaccharides revealed that the level of neutral sugars was higher than that of acidic sugars in EC, while the opposite was true in NC. Gaschromatographic analysis of neutral sugars in pectic fractions revealed that EC and SE were rich in arabinose, while NC was rich in galactose. On the basis of these results, we discuss the possible involvement of neutral sugars, and of arabinose and galactose in particular, in pectic polysaccharides in intercellular contacts.