Fig. 4.

Low root-exudate concentration has a dual effect on nematode activity. (A) The number of oscillations per minute was significantly increased when the EPN Heterorhabditis bacteriophora was exposed to 1.5×-diluted exudates (grey bar) as compared to those in water (white bar). The original (1×) concentration of exudate induced almost complete quiescence in the exposed EPN. (B) The plant-parasitic nematode Heterodera glycine oscillation counts were higher in diluted exudate as compared to the original concentration. Whereas quiescence induction was incomplete at low concentration, the plant-parasitic nematode oscillation activity was still almost 3-fold lower than observed in water alone. (C) A similar pattern was observed for the plant-parasitic nematode Meloidogyne incognita. Letters indicate statistical differences. Bars indicate SEM.