ABSTRACT
This chapter discusses some possible, ecological roles of saponins, and, in particular, will focus on saponin glycosides of alfalfa. Birk reported that alfalfa saponins could be isolated from the dry and sieved soil where alfalfa had been grown, but the origin of these saponins was not explained. Most studies evaluated alfalfa saponins and their activity against alfalfa pests, but some in vitro and field experiments were performed on other insects. Zentmyer and Thompson demonstrated that efficacy of alfalfa saponins against Phytophthora cinnamomi in vitro differed significantly from that determined in soil. The general consensus has been that the major effect of saponins on microorganisms was interaction with membrane sterols. Zanhic acid tridesmoside was detected 12 days after germination began. Most of the saponins can be found in root epidermal tissues, while tissues toward the root axis were void of saponins.
