In Arabidopsis,IQM family has six members and IQM1 is a Ca²⁺-independent calmodulin-binding protein.We previously found that the loss-of-function mutant iqm1 displayed a smaller stomatal aperture and a shorter primary root,and did not obviously change its stomatal aperture when treated with light,darkness or ABA.Here,we constructed a binary expression vector harboring the IQM1 gene,and introduced it into wild-type Arabidopsis,and obtained 10 IQM1 overexpression lines through PCR identification and semiquantitative RT-PCR assay.The IQM1 overexpression lines exhibited significantly bigger and smaller stomatal aperture than wild-type and iqm1-1 when treated with light and darkness,respectively.These lines also showed longer primary root and more lateral root than wild-type and iqm1-1.Besides these IQM1 overexpression lines did not display phenotype in plant growth,bolting,flowering and fruiting.These results further suggest that IQM1 plays an important role in stomatal movement and root growth.