Composition, Properties and Localisation of Pectins in Young and Mature Cells of the Mung Bean Hypocotyl

Two pectic fractions were extracted along the growth gradientof the mung bean hypocotyl. The first one (PF₁) contained pectinssoluble in boiling water and characterized by low uronic acids/cationsratio, high esterification degree and high neutral sugars/acidicsugars ratio. The second one (PF₂) contained pectins insolublein boiling water characterized by high uronic acids/cationsratio, low esterification degree, very low neutral sugar contentand a high selectivity for calcium. Water soluble pectins werepresent in all the wall area whereas the other ones were detectedmainly in the middle lamella. The PF₁/PF₂ ratio was high infast growing tissues but low in mature, slowly growing tissues.The development of the cell wall exchange properties along thegrowth gradient was related to the changes observed in the PF₁/PF₂balance. (Received July 31, 1985; Accepted January 20, 1986)