**4. Conclusions**

The previous survey carried out allows us to discern which were the main technical parameters of the artificial lighting systems used in horticultural nurseries in southern Spain as well as the degree of their implementation. The results obtained in this experiment reported that the most efficient systems with a high value of η and low value of VEEI were XTRASUNLED and TLD-18 lamps. Regarding the level of irradiance, the lamps with the lowest total irradiance were CF but the combination with LEDs increased the value of the total irradiance. The lamps with the highest values of total irradiance were TLD58-6 lamps and the stage of GG in XTRASUN LEDs. Nevertheless, while considering the use of lamps in seedling production, two parameters have been proposed (ELIplant and UIplant) relating the power light emission of the lamp with the light absorption by leaves. The effectiveness of light irradiance (ELIplant) was slightly higher in the case of cucumber than that of tomato for all essayed lamps. It can be found in our experiment that LEDs showed the lowest values, while TL5-6 lamps presented the highest values. Nevertheless, the use of irradiance was similar in both species and higher for blue, red, and violet (around 90%) LEDs, medium for FL and their combinations (around

80%) and lower for CF, LEDs-W and XTRASUN LEDs GG and infrared (IR). In this sense, novelty lamps (XTRASUN LEDs) supposed an improvement of the limit value of energy efficiency and the UI for plants as well as a high versatility related to MAR effects. The advantage of artificial lighting systems in nurseries is mainly related to the technological development of this industry that allows nursery growers to produce quality seedling plants in a shorter growing period. Nevertheless, the lack of knowledge among nursery growers concerning the accurate light requirements in horticultural nurseries involves a delay to the implantation of this technology. In this sense, this work shows the current extent of knowledge of artificial lighting systems, showing different alternatives of light sources that can be used in the growth of seedling plants, and the implementation of specific agronomic indexes such as ELIplant and UI to choose the light sources which are more suitable for use in nursery growing systems, ultimately allowing energy saving and the improvement of quality in seedling plants.

**Author Contributions:** The authors contributed equally to this work.

**Funding:** This research received no external funding.

**Acknowledgments:** The authors thank Dimitrios Tsokanos for his English style corrections.

**Conflicts of Interest:** The authors declare no conflict of interest.
