Abstract: To figure out the allelopathy effects of aquatic extracts from Mirabilis himalaica roots，we used wheat and mung bean as target plants for this study. Results showed that the cell and tissue morphologies of the two target plants were in significantly allelopathy and inhibitory effects after the treatment by the aquatic extracts from M. himalaica roots for 8 d. We observed and analyzed the root morphology and cell structure of the two crops treated with the aquatic extracts using transmission electron microscopy and scanning electron microscopy. The root tip structure in wheat and mung bean were incomplete，part of the epidermis cell felled off，the space between the cells turned larger，interstitial faulting and cavity appeared，and tightly structure between cells were disrupted. In the cell of wheat and mung bean root，membrane shrank，plasmolysis appeared，vacuoles in the cytoplasm turned bigger，nucleus ablated，and the structure of main organelles such as endoplasmic reticulum，mitochondria and Golgi apparatus varied or collapsed and depleted in numbers；i.e.，plant life severely restrained. These results imply that the aquatic extracts from M. himalaica roots presented the strong allelopathic inhibition on two common crops.

Key words: Mirabilis himalaica, allelopathy effect, plant morphology, cell structure