Allelopathic Effects of Cucumber Organs' Extract on Growth Indices of Cucumber (Cucumis Sativus L.), Eggplant (Solanum melongena L.), Pepper (Capsicum annum L.), and Tomato (Lycopersicum esculanum M.) Seedlings

Some crops have been observed to posses effects of allelopathic type. It would be interesting and useful as well to study these plants' allelopathic effects on other crop plants, particularly in rotation and intercropping. So, in this study, the allelopathic potential of cucumber organs' extract on seedling growth of cucumber, eggplant, pepper, and tomato was evaluated using a randomized factorial experiment, in a hydroponic system under greenhouse conditions. In this research, the first variable was plant type (cucumber, eggplant, pepper, and tomato) while the second one cucumber organ type (leaf, root, or stem) extract. Alcoholic extracts (5% w/v) of leaf, root, and stem of cucumber were prepared. The extracts' effects on plant growth indices namely: number of leaves and flowers, root and shoot length, root and shoot fresh weight, as well as root and shoot dry weight were investigated. Results showed that all cucumber organ extracts exert significant inhibiting effect on growth indices of all tested plants. Under the allelopathic effect of cucumber organ extracts, eggplant and cucumber faced the most respective reduction in growth, in comparison with other plants tested. Therefore, it becomes evident that cucumber exerts the most allelopathic effect on eggplant. Also, a considerable reduction of cucumber growth could be attributed to self-toxicity in cucumber. In comparison with other cucumber organ extracts, root extract has the most retarding effect on plant growth. So, can be said that it has the most allelopathic effect. This phenomenon could be attributed to an initial production of allelopath chemicals in roots.