## 3 Results and Discussion
### Daughter Plants and Stolons
Furthermore, the cost of electricity per daughter plant was estimated to be $0.029 to $0.036 for the 01 to 12 week cycle and $0.005 to $0.008 for the 12 to 21 week cycle. The cost for lighting often represents the largest production cost in PIP systems [38; 39]; however, the cost estimated, in the present study, is relatively low on a per plant basis. It is important to understand the main assumptions made for the calculation, since they can significantly impact the results. For example, a plant density of 5.4 plants m\({}^{-2}\) was used for the calculation (density used in this experiment). However, typical strawberry plant density in controlled environments can be up to 10 plants m\({}^{-2}\) (using higher plant density could further decrease cost). It was also assumed that all daughter plants produced are able to root and become a usable transplant. However, daughter plants, in this experiment, range in size and also range in their capability to root (see result Section 3.2). The lamp electrical efficacy used for the calculation was based on high efficiency LEDs with a spectrum different than the one in this experiment. A different spectrum can change (increase or decrease) the propagation efficacy to PPFD  
Figure 5: Propagation efficacy to photosynthetic photon flux density (PPFD) (daughter plants mol\({}^{-1}\)). Arrows represent the removal of all daughter plants after 12 weeks. Triangles, squares, and circles represent 250-PPF, 350-PPF, and 450-PPF light treatments, respectively. Open markers represent data collected for the 01 to 12 week cycle and filled markers represent data collected for the 12 to 21 week cycle. Solid line represents significant linear regression with \(p\leq 0.05\). (daughter plants mol\({}^{-1}\)). Nevertheless, more research is needed to further optimize and validate the use of PIP systems for the profitable production of strawberry daughter plants. These results offer the first available information on the potential cost of lighting for the propagation of strawberry plants in PIP systems. The cumulative number of daughter plants over time during weeks 01 to 12 and 12 to 21 increased linearly per week for both cycles and all light intensities (Figure 6). In the 01 to 12 week cycle, plants grown in 450-PPF had a greater rate of 7.3 daughter plants per week per stock plant (plants wk\({}^{-1}\) stock\({}^{-1}\)) than plants in the 250-PPF and 350-PPF treatments which had a production rate of 5.1 to 5.9 plants wk\({}^{-1}\) stock\({}^{-1}\). In the 12 to 21 week cycle, all treatments had a similar rate of daughter plant production of 6.7 to 7.9 plants wk\({}^{-1}\) stock\({}^{-1}\) (Figure 6). On the basis of this experiment, the PIP propagation system produces an average rate of 6.7 plants wk\({}^{-1}\) stock\({}^{-1}\) (average of all rates from Figure 6) which translates to 36.2 plants wk\({}^{-1}\) m\({}^{-2}\) (at 5.4 stock plant m\({}^{-2}\) density). This number could be used to estimate the size of a facility to meet a particular demand on a specific season, for example, one-meter square would be able to produce 1881 daughter plants yr\({}^{-1}\). For the 01 to 12 week cycle, the total number of stolons per stock plant (3.2-3.7) was similar between light treatments (Figure 7). For the 12 to 21 week cycle, the stolon number per stock plant in 350-PPF (8.4) and 450-PPF (8.5) treatments was 38% greater than in 250-PPF (6.1) (Figure 7). The total number of stolons per plant was 2.3 times greater in the 12 to 21 week cycle than that of the 01 to 12 week cycle. For both growing cycles, stock plants allocated more dry mass to the daughter plants than the stolons. However, the percent dry mass allocation to the stolon was greater in the 12 to 21 week cycle (Table 3). For both growing cycles, the number of daughter plants per stock plant was the same, but it was evident, for the 12 to 21 week cycle, that the plants increased stolon formation (branching) after the removal of all stolons during Week 12.