The wild type Arabidopsis thaliana and its mutants in which heterotrimeric G protein α subunit gene GPA1 was null (gpα1-1,gpα1-2) or over-expressed (wGα,cGα) were used as main materials.Some morphological parameters in plants were measured.Results showed that the null mutants had longer plants,wider leaves and longer legumen stems,compared with the wild type.While some parameters in over-expression mutants,such as leaf shape,were also different from that in wild type.The results show that the α subunit of heterotrimeric G protein participated in modulating growth and development of some organs in Arabidopsis,mainly act as a negative regulator for elongation.