## 3 Results and Discussion
This is due to the fact that the low storage temperature decreases the maturation processes of the fruits and as a result also reduces their accumulation of lycopene. However, for both storage conditions, the fruits of the plants with NaCl presented the lowest contents of lycopene. After 15 days of storage, the behavior of the fruits of the different treatments evaluated was completely different from the previous evaluation. Under conditions of room temperature, the fruits of the T0 plants presented the lowest content of lycopene, while the fruits of the plants with NaCl were the ones with the highest content. The fruits of the rest of the treatments were also superior to the T0 under this condition. On the other hand, under refrigeration, the fruits of the T0 plants showed the highest content of lycopene, while the fruits of the plants with application of Cu NPs had the lowest content. After 23 days of storage under refrigeration, the fruits of the T0 plants had the highest content of lycopene followed by the fruits of the plants with NaCl. In this case, the fruits of the plants with Cu NPs and NaCl presented the lowest lycopene content. Lycopene is the most abundant carotenoid in tomato fruits, in addition to being one of the main antioxidants [1; 3]. It has previously been shown that Cu NPs in Cs-PVA hydrogels when applied to the substrate increase the lycopene content in tomato [2]. Other studies have shown that foliar and in soil application of ZnO NPs and TiO\({}_{2}\) NPs increased lycopene content in tomato [36]. This was not consistently observed in the present study, possibly due to the high stress condition. Under conditions of high stress, an oxidative burst can be generated resulting in the opposite effect [9]. The \(\beta\)-carotene content in tomato fruits was different between treatments at all evaluation times (Table 4). At the time of harvest, the fruits of the plants with application of Cu NPs presented the highest content of \(\beta\)-carotene, while the fruits of the plants corresponding to the treatment with salinity had the lowest content. The fruits of the plants with application of Cu and NaCl NPs were also superior to the fruits of the plants with NaCl, indicating a beneficial effect of the application of Cu NPs mitigating the negative effect of salinity. At eight days of storage once more the fruits of the plants with application of Cu NPs were the ones with higher contents of \(\beta\)-carotene at room temperature along with the fruits of the plants with application of Cu NPs plus NaCl. It was also observed that the fruits of the plants with salinity had the lowest content of this \(\beta\)-carotene same as the previous evaluation. In refrigeration, the fruits of the T0 plants along with the fruits of the plants with application of Cu NPs presented the highest content of \(\beta\)-carotene. This indicates that the stress caused by the application of NaCl significantly decreases the \(\beta\)-carotene content in tomato fruits after eight days of storage regardless of the temperature condition. At 15 days of storage, regardless of temperature, all treatments showed an increase in \(\beta\)-carotene content. At room temperature, the fruits of the plants with application of Cu NPs presented the highest \(\beta\)-carotene content. The T0 under this condition had the lowest content. However, in refrigeration, the fruits of the plants of the two treatments that included the application of NaCl were those that had the highest \(\beta\)-carotene content. This indicates that the application of Cu NPs induces the formation and preservation of \(\beta\)-carotene when the fruits are stored at room temperature. This fact is very important, since \(\beta\)-carotene is the second most important carotenoid in the tomato and is an important antioxidant compound in human health [1]. As already mentioned, Cu NPs are believed to function as inducers of antioxidant compounds [11]. In addition, it has been demonstrated that the application of Cu NPs to the substrate induces the formation of lycopene in tomato [2].