Reducing nitrogen fertilization application in Cucumber by mycorrhiza colonization of the plant

The effect of different nitrogen levels on plant growth, phenol content, antioxidant and Nitrate reductase )NR) activity of cucumber (Cucumis sativus cv. Super) inoculated with mycorrhiza­ was studied. A factorial experiment based on a completely randomized design (CRD) with 6 replicates was designed. Treatments were three levels of nitrogen (NO3-50, NO3-75 and NO3-100) and two mycorrhiza inocula (1000 spore (AM1), 2000 spore (AM2) and no mycorrhiza treatment (AM0) as the control. Results showed that the root fresh weight increased by mycorrhiza inoculation at all nitrogen levels, while it was unaffected by nitrogen levels and mycorrhiza inoculation. FV/FM was higher in NO3-75 mycorrhizal inoculated plants compared to that of AM0 ones. Antioxidant activity of plants increased due to mycorrhiza symbiosis in nitrogen deficiency treatments, so that AM1 and AM2 increased antioxidant activity in NO3-50 and NO3-75 treatments, respectively, as compared to the AM0 plants. The highest NR activity was observed in the NO3-50 treatment. However, mycorrhiza inoculation decreased NR activity of the plants at all nitrogen levels. Therefore, it can be concluded that mycorrhiza inoculation, especially the 1000 spores treatment (AM1), and a moderate level of NO3 (NO3-75) can be used and these application levels can be very effective for greenhouse cucumber production.