*4.4. Experimental Design and Statistical Analysis*

The experiment design was a randomized complete block with a split-plot with one metal shelving rack as a block, 3 blocks, six PPFD levels as the main treatment, and the two crops as the split plot. The experimental unit was a group of nine plants. Regression analyses (linear, quadratic, sigmoidal, and exponential rise to maximum) were conducted with time or average PPFD of each treatment as the independent variable (SigmaPlot 11.0, Systat software, Inc., San Jose, CA, USA). Finally, multiple regression analysis (α < 0.05) was performed using SAS (SAS University edition; SAS Institute, Cary, NC, USA) with PPFD as a continuous and species as a class variable to test for PPFD and species effects on PCS, incident light over the growing period, CCI, ACI, ΦPSII, CO<sup>2</sup> assimilation, leaf area, canopy overlap ratio, dry weight, SLA, and LUE. When there was no significant interaction between species and PPFD, the interaction term was removed from the model and the main effects of species and PPFD were used to describe the treatment effects.

**Supplementary Materials:** The following supplementary figures are available online at https: //www.mdpi.com/article/10.3390/plants10040704/s1, Figure S1. The projected canopy images captured during the growing period of mizuna (*Brassica rapa* var. *japonica*) (A–D) and lettuce (*Lactuca sativa* 'Green Salad Bowl') (E–H) grown at 425 µmol m−<sup>2</sup> s −1 . The first three images of mizuna (A–C) and lettuce (E–G) were captured at 5 (A,E), 15 (B,F), and 19 days (C,G) after seeding. The last images of mizuna (D) and lettuce (H) were captured during the harvest (27 and 28 days, respectively); Figure S2. Correlation between early projected canopy size (lettuce at 10 days and mizuna at 8 days, after seeding) and final shoot dry weight of lettuce (*Lactuca sativa* 'Green Salad Bowl') and mizuna (*Brassica rapa* var. *japonica*); Figure S3. Correlation between specific leaf area (leaf area/shoot dry weight) and chlorophyll content index (CCI) of lettuce (*Lactuca sativa* 'Green Salad Bowl') and mizuna (*Brassica rapa* var. *japonica*); Figure S4. The appearance of lettuce (*Lactuca sativa* 'Green Salad Bowl', top) and mizuna (*Brassica rapa* var. *japonica*, bottom) at the end of the growing

cycle for plants grown at six different photosynthetic photon flux densities (upper left corner of each picture).

**Author Contributions:** Conceptualization, T.C.J., and M.W.v.I.; methodology, T.C.J. and M.W.v.I.; formal analysis, T.C.J. and M.W.v.I.; investigation, T.C.J. and M.W.v.I.; data curation, T.C.J.; writing original draft preparation, T.C.J.; writing—review and editing, T.C.J. and M.W.v.I.; visualization, T.C.J.; supervision, M.W.v.I.; funding acquisition, M.W.v.I. Both authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the U.S. Department of Agriculture–National Institute of Food and Agriculture–Specialty Crop Research Initiative Award No. 2018-51181-28365 (Project "Lighting Approaches to Maximize Profits". www.hortlamp.org).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Data used in this study is available at https://drive.google.com/ drive/folders/1BgP771XRRsbZHCttrHB-SueqV4nU0JMf.

**Acknowledgments:** We thank Eleanor Jane Rager for her assistance with data collection and Fluence Bioengineering for donating the light fixtures.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
