Morphophysiological and biochemical traits of cucumber and black nightshade under allelopathic compounds of eucalyptus aqueous extract and mulch

The present study was performed to evaluate and compare the allelopathic effects of leaf aqueous extract and mulch of Eucalyptus (Eucalyptus globulus Labill.) on cucumber (Cucumis sativus var. beith alpha) and black nightshade (Solanum nigrum L.) seedlings in a completely randomized design. 21 days after treatment of seedlings with leaf aqueous extract (concentrations 5, 10, 15, 20 g L-1) and mulch (3% and 5% weight/volume), some morphological traits, membrane stability, proline and malondialdehyde content, total protein content and activity of polyphenol oxidase, and guaiacol peroxidase were analyzed. According to the results, although both aqueous extracts and mulch reduced the height and dry weight of aerial parts and the dry weight of roots in cucumber and black nightshade (compared to the control), the length of cucumber roots increased under the treatment of all the concentrations of aqueous extracts and mulch 3%. Evaluation of membrane stability index, proline and malondialdehyde content showed that the negative effect of mulch (3% and 5%) on black nightshade is significant. The treatment with aqueous extracts increased the activities of polyphenol oxidase and guaiacol peroxidase enzymes in cucumber (compared to the control), with the maximum ones in 20 g L-1 extract, while treatment with these extracts on black nightshade reduced the soluble protein content and enzymes studied. Overall, according to the results of this study, it can be stated that aqueous extracts showed a better ability to control black nightshade compared to leaf mulch, and it may be possible to use this type of treatment for herbicides in vegetable fields.