ROOT HAIR DEFORMATION ACTIVITY OF NODULATION FACTORS AND THEIR FATE ON VICIA-SATIVA

We used a semiquantitative root hair deformation assay for Vicia sativ a (vetch) to study the activity of Rhizobium leguminosarum bv viciae n odulation (Nod) factors. Five to 10 min of Nod factor-root interaction appears to be sufficient to induce root hair deformation. The first d eformation is visible within 1 h, and after 3 h about 80% of the root hairs in a small susceptible zone of the root are deformed. This zone encompasses root hairs that have almost reached their maximal size. Th e Nod factor accumulates preferentially to epidermal cells of the youn g part of the root, but is not restricted to the susceptible zone. In the interaction with roots, the glucosamine backbone of Nod factors is shortened, presumably by chitinases. NodRlv-IV(C18:4,Ac) is more stab le than NodRlv-V(C18:4,Ac). No correlation was found between Nod facto r degradation and susceptibility. Degradation occurs both in the susce ptible zone and in the mature zone. Moreover, degradation is not affec ted by NH4NO3 and is similar in vetch and in the nonhost alfalfa (Medi cago sativa).