**5. Conclusions**

We have experimentally investigated the effect of LED illumination spectra on the growth of sweet basil plants. Specifically, the plant fresh mass (g), plant dry mass (g), energy use efficiency (EUE), water use efficiency (WUE), and plant cultivation cycle were measured for sweet basil plants grown in three different grow tents illuminated with (i) white (W\*), (ii) blue (B) and red (R); and (iii) blue (B), red (R) and far-red (F) LED spectra. Post hoc analyses have revealed that the BRF\*- and BR\*-illuminated tents produced, respectively, 83% and 42% higher average fresh biomass than that produced in the W\*-illuminated tent. For the average dry mass, results have shown that the BRF\*- and BR\*-illuminated tents produced, respectively, 100% and 51% higher average dry biomass than that produced in the W\*-illuminated tent. Results have also shown that, after 6 weeks, the average biomass of the basil plants grown in the W\*-illuminated tent is 93% of the average biomass per

plant grown over a period of 4 weeks in the BRF\*-illuminated tent, and that, more than 60% of the basil plants grown in the W\*-illuminated tent bolted after 6 weeks, whereas the basil plants were bolting-free after 4 weeks. These results have demonstrated that the BRF\*-illumination treatment enables higher crop yield and quality (no bolting) in comparison with the W\*-illumination treatment.

In addition, experimental results have shown that the water usage efficiency with the BRF\* spectrum was 24 g FW L−<sup>1</sup> H2O, compared to 13 g FW L−<sup>1</sup> H2O, and 18 g FW L−<sup>1</sup> H2O for the W\*- and BR\*-spectra, respectively. Moreover, results have revealed that the electricity usage efficiency with the BRF\* spectrum was 80 <sup>±</sup> 4.8 g FW kW−<sup>1</sup> , compared to 46 ± 1.7 g FW kW−<sup>1</sup> and 65 <sup>±</sup> 8.6 g FW kW−<sup>1</sup> for the W\* and BR\* spectra, respectively. Therefore, the results of this study have demonstrated the commercial viability of both BRF\*-, and BR\*-illuminated grow tents compared to the commonly used W\*-illuminated counterparts.

The protected environment results presented in this work paves the way towards the development of glass greenhouses employing spectrally selective optical coatings that pass the optimum solar spectral components through, which significantly increase the yield of sweet basil.

**Author Contributions:** Conceptualization, M.M.R., M.V. and K.A.; data curation, M.M.R., M.V. and K.A.; formal analysis, M.M.R., M.V. and K.A.; funding acquisition, K.A.; investigation, M.M.R., M.V. and K.A.; methodology, M.M.R., M.V. and K.A.; project administration, M.M.R. and K.A.; resources, M.M.R., M.V. and K.A.; software, M.M.R. and M.V.; supervision, M.V. and K.A.; validation, M.M.R., M.V. and K.A.; visualization, M.M.R. and K.A.; writing—original draft, M.M.R., M.V. and K.A.; writing—review and editing, M.M.R., M.V. and K.A. All authors have read and agreed to the published version of the manuscript.

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

**Data Availability Statement:** The datasets generated and/or analysed during this study are available from the corresponding author on reasonable request.

**Acknowledgments:** The research was supported by Edith Cowan University (ECU), Australia. The authors wish to thank Jacqualine Anne Thomas, Mohammad Nur E Alam, Sretan Askraba, Paul Roach, our colleagues at Edith Cowan University for their suggestions on preparing the manuscript. We are also grateful for the insightful comments offered by the anonymous peer reviewers.

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