*3.3. Fruit Set and Survival Are Enhanced in Illuminated Western-Facing Plants*

Following the data we obtained in the earlier experiment for winter fruit set and survival in E- and W-facing plants (Figure S3), we also assessed the data shown in Figure 4D separately for E and W. Figure 5 shows the fruit set and survival in the three treatments of the study (CR, LED-D, LED-N) in E- and W-facing plants. For each treatment, E is shown by the lighter-colored lines and W by the darker-colored lines of the same shade. In illuminated sections of either LED-D or LED-N, the fruit set was higher in W-facing plants as compared to E-facing ones of the same treatment (Figure 5A). Nonetheless, in CR sections, the fruit set was nearly identical in E- and W-facing plants. The highest number of fruitlets was observed in LED-N-W plants (Figure 5A, orange line), 76% higher than CR-W. From the light treatments, LED-D-E had the lowest, but still considerably high, number of fruitlets, 48% higher than CR-E. The number of surviving fruit (Figure 5B) reflects that of the fruit set. Only W-facing plants, of both LED-D and LED-N, exhibited a significantly higher number of surviving fruit as compared to the CR. These were 78% and 62% higher for LED-N-W and LED-D-W, respectively. The trend for a higher number of fruit in LED-N vs. LED-D was observed in both fruit set and fruit survival, although the differences between the two were not statistically significant.

**Figure 4. Supplemental intra-canopy illumination increases fruit set and survival in the winter.** Fruitlets were labelled along the season in (**A**) control non-illuminated (CR) sections, (**B**) sections illuminated during daytime (LED-D), and (**C**) sections illuminated at the edge of day (LED-N). Whole bars denote the average number ± SD of fruitlets from four sections. In each section, the number of fruitlets was summed for ten plants: five in the eastern-facing row and five in the western-facing row of the same bed. Each section was from a different replicate in the experimental plot, see Figure 2) labelled on the noted dates. Colored portion of the bar shows the fraction of surviving fruits from the total. At the end of the experiment (07.05.20 bar), fruitlets remaining on the plants were counted without follow-up for survival. Black brackets denote the winter time period between the two big fruit set waves of control non-illuminated plants (**A**). (**D**) Cumulative number of fruitlets (dashed lines) and surviving fruit (solid lines) during the winter, corresponding to the period marked by the brackets in (**A**–**C**). Distinct upper- and lower-case letters denote statistically significant differences (*p* < 0.05) for the total number of labelled fruitlets and for surviving fruit, respectively. **Figure 4. Supplemental intra-canopy illumination increases fruit set and survival in the winter.** Fruitlets were labelled along the season in (**A**) control non-illuminated (CR) sections, (**B**) sections illuminated during daytime (LED-D), and (**C**) sections illuminated at the edge of day (LED-N). Whole bars denote the average number ± SD of fruitlets from four sections. In each section, the number of fruitlets was summed for ten plants: five in the eastern-facing row and five in the western-facing row of the same bed. Each section was from a different replicate in the experimental plot, see Figure 2) labelled on the noted dates. Colored portion of the bar shows the fraction of surviving fruits from the total. At the end of the experiment (07.05.20 bar), fruitlets remaining on the plants were counted without follow-up for survival. Black brackets denote the winter time period between the two big fruit set waves of control non-illuminated plants (**A**). (**D**) Cumulative number of fruitlets (dashed lines) and surviving fruit (solid lines) during the winter, corresponding to the period marked by the brackets in (**A**–**C**). Distinct upper- and lower-case letters denote statistically significant differences (*p* < 0.05) for the total number of labelled fruitlets and for surviving fruit, respectively.

#### *3.3. Fruit Set and Survival Are Enhanced in Illuminated Western-Facing Plants 3.4. Daily Light Integral and Photosynthetic Activity of the Eastern- and Western-Facing Canopy*

Following the data we obtained in the earlier experiment for winter fruit set and survival in E- and W-facing plants (Figure S3), we also assessed the data shown in Figure 4D separately for E and W. Figure 5 shows the fruit set and survival in the three treatments of the study (CR, LED-D, LED-N) in E- and W-facing plants. For each treatment, E is shown by the lighter-colored lines and W by the darker-colored lines of the same shade. In illuminated sections of either LED-D or LED-N, the fruit set was higher in W-facing plants as compared to E-facing ones of the same treatment (Figure 5A). Nonetheless, in CR sections, the fruit set was nearly identical in E- and W-facing plants. The highest number of fruitlets was observed in LED-N-W plants (Figure 5A, orange line), 76% higher than CR-W. From the light treatments, LED-D-E had the lowest, but still considerably high, number of fruitlets, 48% higher than CR-E. The number of surviving fruit (Figure 5B) reflects that of the fruit set. Only W-facing plants, of both LED-D and LED-N, exhibited a significantly higher number of surviving fruit as compared to the CR. These were 78% and 62% higher for LED-N-W and LED-D-W, respectively. The trend for a higher number To better understand the differential effect of the intra-canopy illumination on E- and W-facing plants, we also probed the natural light conditions and photosynthetic activity at the outer parts of the canopy in these plants. PAR was recorded at the E- and W-facing outer canopy and the daily light integral (DLI) was calculated from the recorded values. Note the positioning of the experimental tunnel, with 'eastern' plants inclined (~25◦ ) toward the north and 'western' plants toward the south (Figure 2). Figure 6 depicts PAR recordings and the derived DLI at the E- and W-facing canopy and above the canopy on two representative sunny days during the winter. On these days, the DLI inside the tunnel, covered by the polyethylene sheet, was 21 and 24 mol photons m−<sup>2</sup> d −1 . PAR sensors at the E- and W-facing canopy were positioned such that they mimic light capture by the canopy. The recordings made at the E- and W-facing canopies show that the DLI at the latter was 2.5-fold (January) and 2-fold (February) higher (Figure 6). Higher DLI values, at both sides of the canopy, were recorded in February as compared to January, as expected when days become longer toward the spring. For E-facing plants, the peak in light intensity

was around 9:00–9:30, while for W-facing plants, the peak was between 14:00 and 15:00. Furthermore, the light intensity during peak times was much higher for W-facing plants. of fruit in LED-N vs. LED-D was observed in both fruit set and fruit survival, although the differences between the two were not statistically significant.

**Figure 5. Fruit set and survival in eastern- and western-facing plants.** (**A**) Cumulative number of fruitlets labelled during the winter in the eastern (E)- and western (W)-facing plants of control nonilluminated (CR) sections, and in the E- and W-facing sections illuminated during daytime (LED-D) or edge of day (LED-N). Values shown represent the average number ± SD of fruitlets from four E or W sections, each from a different replicate in the experimental plot, see Figure 2). For each E or W section, fruitlets were summed for five plants. (**B**) Cumulative surviving fruit from the E- and Wfacing plants of the different treatments, corresponding to the fruitlets that were labelled (**A**). Distinct letters denote statistically significant differences (*p* < 0.05) between the six groups. Data shown in this figure are the same data shown in Figure 4D, separated to E and W. **Figure 5. Fruit set and survival in eastern- and western-facing plants.** (**A**) Cumulative number of fruitlets labelled during the winter in the eastern (E)- and western (W)-facing plants of control non-illuminated (CR) sections, and in the E- and W-facing sections illuminated during daytime (LED-D) or edge of day (LED-N). Values shown represent the average number ± SD of fruitlets from four E or W sections, each from a different replicate in the experimental plot, see Figure 2). For each E or W section, fruitlets were summed for five plants. (**B**) Cumulative surviving fruit from the Eand W-facing plants of the different treatments, corresponding to the fruitlets that were labelled (**A**). Distinct letters denote statistically significant differences (*p* < 0.05) between the six groups. Data shown in this figure are the same data shown in Figure 4D, separated to E and W.

*3.4. Daily Light Integral and Photosynthetic Activity of the Eastern- and Western-Facing Canopy*  To better understand the differential effect of the intra-canopy illumination on E- and W-facing plants, we also probed the natural light conditions and photosynthetic activity at the outer parts of the canopy in these plants. PAR was recorded at the E- and W-facing outer canopy and the daily light integral (DLI) was calculated from the recorded values. Note the positioning of the experimental tunnel, with 'eastern' plants inclined (~25°) toward the north and 'western' plants toward the south (Figure 2). Figure 6 depicts PAR recordings and the derived DLI at the E- and W-facing canopy and above the canopy on two representative sunny days during the winter. On these days, the DLI inside the tunnel, covered by the polyethylene sheet, was 21 and 24 mol photons m−2 d−1. PAR sensors at the E- and W-facing canopy were positioned such that they mimic light capture by the The photosynthetic activity of plants on the two sides was probed during light peak morning and afternoon hours, using gas exchange measurements of attached outer-canopy leaves (Figure 7). CO<sup>2</sup> assimilation rates were similar (~6 µmol m−<sup>2</sup> s −1 ) for the outer canopy side not subjected to direct sunlight: in the morning for W-facing plants and in the afternoon for E-facing plants (Figure 7A). However, the assimilation rates of the Wfacing canopy in the afternoon were ~25% higher than those of the E-facing canopy in the morning (Figure 7A). This is due to both the higher light intensity (Figure 7F) and higher leaf temperature (Figure 6E) on the W in the afternoon as compared with E in the morning. Cooling of the canopy via evapotranspiration is prominent for W-facing plants in the afternoon (Figure 7C). The resultant enhanced gas exchange (Figure 7B) contributes toward CO<sup>2</sup> assimilation in these plants. Lower intercellular CO<sup>2</sup> is supportive of the higher assimilation in W-facing plants during the afternoon (Figure 7D).

canopy. The recordings made at the E- and W-facing canopies show that the DLI at the latter was 2.5-fold (January) and 2-fold (February) higher (Figure 6). Higher DLI values, at both sides of the canopy, were recorded in February as compared to January, as expected when days become longer toward the spring. For E-facing plants, the peak in light intensity was around 9:00–9:30, while for W-facing plants, the peak was between 14:00 and 15:00. Furthermore, the light intensity during peak times was much higher for W-

facing plants.

**Figure 6. Photosynthetically-active radiation of sunlight at the outer canopy of eastern- and western-facing plants.** Photosynthetically-active radiation (PAR; 400–700 nm) shown for two sunny days: (**A**) 6 January 2020 and (**B**) 17 February 2020, was recorded above the canopy (at a height of ~3 m), and at the outer canopy of eastern- and western-facing rows at a height of 1 m. Derived values of the daily light integral (DLI, in mol photons m<sup>−</sup>2 d−1) at the different positions are denoted by arrows. **Figure 6. Photosynthetically-active radiation of sunlight at the outer canopy of eastern- and western-facing plants.** Photosynthetically-active radiation (PAR; 400–700 nm) shown for two sunny days: (**A**) 6 January 2020 and (**B**) 17 February 2020, was recorded above the canopy (at a height of ~3 m), and at the outer canopy of eastern- and western-facing rows at a height of 1 m. Derived values of the daily light integral (DLI, in mol photons m−<sup>2</sup> d −1 ) at the different positions are denoted by arrows. *Plants* **2022**, *11*, 424 12 of 17

**Figure 7.** Gas-exchange parameters of the outer canopy of eastern- and western-facing plants in the morning vs. afternoon. (**A**) CO2 assimilation rate, (**B**) stomatal conductance, (**C**) transpiration rate, and (**D**) intercellular CO2 of leaves of the outer canopy in eastern (E)- and western (W)-facing plants assayed in the morning (am, 8:50–9:30) and afternoon (pm, 13:50–14:30). (**E**) Leaf temperature and (**F**) light intensity (PAR) were recorded during the gas-exchange measurements. Values shown represent means ± SD of 14 leaves (am) and 10 leaves (pm) measured non-destructively. **Figure 7.** Gas-exchange parameters of the outer canopy of eastern- and western-facing plants in the morning vs. afternoon. (**A**) CO<sup>2</sup> assimilation rate, (**B**) stomatal conductance, (**C**) transpiration rate, and (**D**) intercellular CO<sup>2</sup> of leaves of the outer canopy in eastern (E)- and western (W)-facing plants assayed in the morning (am, 8:50–9:30) and afternoon (pm, 13:50–14:30). (**E**) Leaf temperature and (**F**) light intensity (PAR) were recorded during the gas-exchange measurements. Values shown represent means ± SD of 14 leaves (am) and 10 leaves (pm) measured non-destructively.

The yield in spring from the experimental sections was summed for six harvests (9

present in each side. For E-facing plants, the yield in LED-D was 30% (kg/plant) and 27% (#/plant) higher as compared to the CR, although these did not pass the significance test. In contrast, the differences of yield in LED-N vs. CR sections for E-facing plants were quite small (~12%). The W-facing spring yield for LED-D was 26% (kg/plant) and 17% (#/plant) higher than CR (not significant). Notably, for LED-N, the W-facing spring yield was 43% higher than the CR both by weight and number of fruits. These results are in agreement with those obtained from the fruit survival quantification (Figure 5B), which show that a

significantly higher number of fruits were obtained on the W-facing side.

*3.5. Spring Yield and Plant Biomass* 
