Elicitation of H2 O2 production in cucumber hypocotyl segments by oligo-1,4-α-D-galacturonides and an oligo-β-glucan preparation from cell walls of Phythophthora megasperma f. sp. glycinea.

Abstract

The production of H2 O2 by cucumber hypocotyl segments (Cucumis sativus L. cv. Wisconsin SMR 58) in response to α-1,4-linked oligomers of galacturonic acid and oligo-β-glucans from the cell walls of Phytophthora megasperma f. sp. glycinea was studied. Oligogalacturonides with degrees of polymerization of 9 to 13 elicited H2 O2 production, the most effective being the deca-, undeca- and dodecamers. A similar relationship between size and effect was previously obtained when oligogalacturonides were tested for their ability to elicit lignification in cucumber hypocotyls. The oligogalacturonide-induced increase in H2 O2 concentration was detected after 4 h, reaching a maximum after 10 h of incubation. The glucan elicitor induced lignification at a 100-fold lower concentration than the oligogalacturonides, but yielded only 10% of the maximum H2 O2 accumulation seen with oligogalacturonides. The glucan elicitor-induced H2 O2 production was detectable after 2 h, and reached a maximum after 4 to 6 h. Catalase abolished the elicitation of both phenol red oxidation and lignification in cucumber hypocotyls. At least part of the oligogalacturonide-induced H2 O2 production appeared to be dependent upon de novo protein synthesis.