NOD FACTORS AND TRI-IODOBENZOIC ACID STIMULATE MYCORRHIZAL COLONIZATION AND AFFECT CARBOHYDRATE PARTITIONING IN MYCORRHIZAL ROOTS OF LABLABPURPUREUS

Roots of Lablab purpureusus (L.) Sweet were treated with tri-iodobenzo ic acid (TIBA), kinetin or with nodulation factors (Nod factors) purif ied from Rhizobium sp. NGR234 and grown in the presence of a mycorrhiz al inoculum (Glomus mosseae (Nicol. & Gerd.) Gerdemann & Trappe. Colon ization by the mycorrhizal fungus was increased from < 30% to c. 65%, of root length when roots were treated with these growth regulators, M oreover, treatment of mycorrhizal L. purpureus roots with Nod factors or TIBA strongly induced sporocarp formation of Glomus mosseae. In par allel, the pool size of the fungal disaccharide trehalose was signific antly affected in roots treated with TIBA and Nod factors alone, and w ith TIBA combined with all effecters, and increased from 0.06 mg g(-1) d. wt in control roots to up to 1.7 mg g(-1) d. wt (TIBA+kinetin). Co nversely, the sucrose pool decreased from 5%, d. wt to less than a hal f in roots treated with Nod factors. Activities of trehalase were sign ificantly enhanced in mycorrhizal roots by the treatment with Nod fact ors or TIBA. When Nod factors and TIBA were added in combination, thes e activities were strongly enhanced suggesting synergism between these growth regulators.