Mirko Sodini ¹ Silvia Traversari ^2* Sonia Cacini ³ Irene Gonfiotti ⁴ Anna Lenzi ⁴ Daniele Massa ³

• ¹ Department of Food, Environmental, and Animal Sciences, University Of Udine, Udine, Italy
• ² Research Institute on Terrestrial Ecosystem (IRET), National Research Council (CNR), Pisa, Italy
• ³ Research Centre for Vegetable and Ornamental Crops, Council for Agricultural and Economics Research (CREA), Pescia (PT), Italy
• ⁴ Department of Agriculture, Food, Environment and Forestry (DAGRI), University of Florence, Firenze, Italy

The non-thermal plasma (NTP) technique has been suggested as a sustainable horticultural practice to promote biomass accumulation, nutrient uptake, N metabolism, and disease prevention in plants. In particular, the potentiality of this technique to promote the natural accumulation of nutrients into plants deserve to be explored as input saving is strongly recommended in the horticultural sector. The aim of this work was to test the use of NTP to treat the nutrient solution supplied to a red coloured variety of rocket salad (Diplotaxis tenuifolia L. ‘Dragon’s Tongue’) in relation to the N fertilization level in hydroponic close loop system. Low, medium, and high levels of N (i.e., 1, 10, and 20 mM) were tested in control (no NTP) or NTP treated conditions in two consecutive growing cycles. Results highlighted a N-dependent effect of NTP treatment showing a biomass stimulation at 10 mM N while negative effects of this technique at 1 and 20 mM N. The biomass boosting of NTP found at 10 mM N coupled with an increase in K and Zn showing positive effects also on the nutraceutical aspects. Interestingly, different mechanisms seemed to be involved in the detrimental effects found at low and high N levels, i.e., a lower sensibility to N deficiency at 1 mM and a synergic negative effect of N and NTP in promoting oxidative stress at 20 mM.