XVI International Botanical Congess

Recently, the roles of cAMP and cGMP as plant signaling molecules have been indicated. In the present study, the levels of cAMP and cGMP in phloem and xylem saps from castor bean (Ricinus communis L.) and xylem sap from nodule-forming lines and non-nodulating mutants of Glycine max L. were examined by enzyme immunoassays. The phloem sap from 2-month-old castor bean had significant levels of cAMP (0.16 $B!^ (J0.04 pmol ml-1) and cGMP (0.21 $B!^ (J0.004 pmol ml-1) and the xylem sap contained detectable levels of cAMP (0.02 $B!^ (J0.007 pmol ml-1) and cGMP (0.026 $B!^ (J0.004 pmol ml-1). cAMP and cGMP contents in xylem sap from nodulated lines were higher than those from castor bean. On the contrary, the cAMP and cGMP contents in xylem sap from non-nodulating mutants were lower than from nodulated soybean plants. Previously, we detected high levels of cAMP and significant levels of cGMP in symbiotic nodules. The contents of these nucleotides in phloem and xylem saps were generally lower than in the plant organs on fresh weight basis.