The effect of allelochemicals from Casuarina cunninghamiana branchlets was assessed on the growth and metabolomic content of three recipient plants: (cucumber), Lycopersicon esculentum Mill.(tomato) and Brassica nigra L. (black mustard). The aqueous extract delayed the germination rates of the three species with pronounced effect on B nigra and L. esculentum.The aqueous extract significantly reduced the seeds germination percentage of B. nigra. The shoot and root lengths were reduced significantly under these concentrations and the germination index (GI) registered lower value due to the effect of the extract on root length. Under these concentrations (1-4 %) the seeds germination percentage of L. esculentum was not significantly affected but the root length was dramatically decreased. No significant change either in seeds germination percentage or in the root length up to the concentration of 4 % was recognized in .Application of allelochemicals from germination and growth criteria but also affected the biochemical and metabolomic content in C. sativus. Application of allelochemicals from C. cunninghamiana branchlets not only affected the germination and growth criteria but also affected the biochemical and metabolomic content in the recipient crop species. A significant increase in carbohydrates, proteins and was also observed in L. esculentum and proline content was observed in both plants. Stress on germinated crop seeds resulted in a significant decrease in photosynthetic pigmen cunninghamiana branchets aqueous extract in both plants but the content was increased significantly under the highest concentration in tomato. Sensitivity of the weed allelochemicals from the donner plant may open the door to exploit overcome the growth of weeds species associated to crop plants through using this plant as natural herbicides
