In mung bean (Vigna radiata), 1-aminocyclopropane-1-carboxylate synthase (ACS) is encoded by a multigene family that comprises at least seven members. Their expression is induced by hormones, developmental signals, inhibition of protein synthesis, or stress. We peformed an RT-PCR assay to understand the differential accumulation of transcripts for ACC synthase homologs as a response to Li$^{+}$ in etiolated mung bean hypocotyls. Treating the seedlings with LiCl caused inductions of the ACS1, ACS4, ACS5, ACS6, and ACS7 genes. The induction level of ACS7 was particularly high. This effect on ACS7 expression was specific, lasting more than 8 h after the treatment. To understand the relationship of this Li$^{+}$ action with the phosphoinositide (PI) second messenger system, we examined the effect of $Ca^{2+}$ treatment on Li$^{+}$-induction of the ACS7 gene. Because $Ca^{2+}$ did not reverse the Li$^{+}$ effect, we suggest that regulation of the ACS7 gene by Li$^{+}$ the mung bean may not involve the PI system.the PI system.