Glu triggered Ca2+flux via GLRs. (Toyota et al., 2018; Forde et al.,2014). Glu rapidly induced a sharp spike of Ca2+within 20 s, whichquickly declined to the basal level after the spike (Ni et al., 2016). Also,Meyerhoff et al. found that the Arabidopsis mesophyll cells exhibitedglutamate-induced, desensitizing calcium and membrane-potential tran-sients. And the Glu responses were transient in nature, which weresubject to desensitization (Meyerhoff et al., 2005). In this research, Gluaddition induced sharp Ca2+efflux with high speed, which was similaras Glu&Cd addition (Fig. 4), and the Ca2+signals were subjected todesensitization after the passage of time, which was much higher thanthat with Cd addition, giving a very different net Ca2+influx comparedto Cd by itself (Fig. 1). These results suggest that the immediate activa-tion of Ca2+was caused by Glu, which might play a role as signal forCa2+eliciting. Interestingly, Glu content has been significantly improvedby 24 h Cd shock, but not Ca addition (Fig.3). These results suggestedthat Cd addition enhanced Glu content, which triggered Ca2+efflux. Weshowed here that the expressions of Glutamate receptor 2.7, Glutamatereceptor 2.8, Glutamate receptor 2.1, Glutamate receptor 2.6 and Glu-tamate receptor 2.9 have been significantly up-regulated by Cd treat-ment. These together indicated that function of GLR ion channels hasbeen improved both by up-regulation of gene expression and the acti-vation by Glu. Even until now it was not known whether Glu exerted itseffects through the regulation of amino acids metabolism or via an uni-dentified signaling pathway. The