But viruses and viroids can stimulate the plant to produce these compounds. Enzymes -large protein molecules that catalyze all the interrelated chemical reactions in a living cell. Fungi and parasitic higher plants apparently penetrate wax layers by means of mechanical force alone. Example-wax layer on apples and other fruit. Cutin - an insoluble polyester of mostly branched derivatives of C 16 and C 18 hydroxy fatty acids.
Fungi produce small amts.
When this small amt. Pectic substances - constitute the main component of the middle lamella. They are polysaccharides consisting mostly of galacturonan molecules interspersed with rhamnose molecules and side chans of galacturonan and other sugars. Pectin methyl esterases-removes small branches of pectin chain that does not effect the pectin chain length, but this does affect the solubility and open it up to attack by other enzymes. Polygalacturonase-chain splitting pectinase.