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Article

Yield, Quality, and Resources Use Efficiency of Wild Rocket Baby Leaves Grown under Different Controlled Environment Systems and Various Growing Seasons

by
Dimitrios Mainos
1,
Filippos Bantis
2,
Georgios K. Ntinas
3 and
Athanasios Koukounaras
1,*
1
Department of Horticulture, Aristotle University, 54124 Thessaloniki, Greece
2
Department of Agriculture, University of Patras, 30200 Messolonghi, Greece
3
Institute of Plant Breeding and Genetic Resources, Greek Agricultural Organization-Dimitra, Thermi, 57006 Thessaloniki, Greece
*
Author to whom correspondence should be addressed.
Horticulturae 2023, 9(6), 661; https://doi.org/10.3390/horticulturae9060661
Submission received: 17 May 2023 / Revised: 24 May 2023 / Accepted: 31 May 2023 / Published: 2 June 2023
(This article belongs to the Collection Advances in Greenhouse Horticulture)
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Abstract

:
Wild rocket is a leafy vegetable with economic interest as a consequence of baby leaf ready-to-eat salads. The climate crisis is expected to influence wild rocket production, but these effects could be confronted with cultivation in greenhouses and plant factories with artificial lighting (PFALs). Climate responses are related to growing seasons. Our objective was to test the impact of two growing seasons, winter and summer, on the growth and physiology of wild rocket baby leaves in different controlled environment systems (greenhouse and PFAL). The growth cycle was reduced by 27% in the PFAL compared to the greenhouse during winter. Summer yield was greater in the greenhouse, but leaf number and area were greater in the PFAL. The lowest water use efficiency was recorded in the greenhouse during summer. Energy use efficiency was lower in PFAL compared to the greenhouse. Land use efficiency was not affected by the growing system, but in PFALs it is able to increase it by growing in vertical layers. Relative chlorophyll content and total soluble solids were enhanced in the greenhouse. The photosynthetic efficiency evaluation showed considerable stress in summer-grown plants in the greenhouse, as shown by PIABS and φP0. In general, the production was similar in the PFAL regardless of seasons.

1. Introduction

Wild rocket is a cool-season leafy vegetable that belongs to the Brassicaceae family and is characterized by the spicy taste and aroma of its leaves [1]. Like many species belonging to this family, wild rocket contains various bioactive components such as glucosinolates, phenols, and ascorbic acid, which promote human health, as they exhibit antioxidant and anticancer properties and contribute to the prevention of heart disease [2,3]. The colour is also an important parameter for successful marketing and satisfactory consumer preference, an observation that applies to all green leafy vegetables [4]. In recent years, wild rocket has shown increased interest as a consequence of the global spread of baby leaf ready-to-eat salads and the stronger aroma and flavor of the leaves, compared to Eruca sativa Mill. [5]. Baby leaves are increasingly used in ready-to-eat salads due to their longer shelf life and higher content of nutrients compared to leafy vegetables [6].
The climate crisis is expected to significantly affect global food production [7]. The environmental factors that will affect vegetable crops to a greater extent are the rise of global temperature and greenhouse gas concentration (CO2 and O3) as well as the more frequent occurrence of extreme weather events [8]. Rising temperatures can enhance or act as a limiting factor in crop yield and quality. This depends on the crop and the latitude in which it is cultivated. Mediterranean regions are expected to face the greatest challenge [9]. To overcome these challenges, plants can be grown in controlled environment conditions [10].
Cultivation in a controlled environment has been carried out for several decades around the world, with the main objective of off-season production. This is achieved by modifying environmental factors such as temperature, light, and humidity in order to create favorable growing conditions. In this way, it is possible to increase the yield, reduce the crop cycle duration, and improve the resource-use efficiencies such as energy (EUE), water (WUE), and surface land (LUE) [11]. One of the most common systems of controlled environment agriculture is the greenhouse. In modern greenhouses, sensors and automated control systems are used in order to regulate growing conditions [12]. However, the greenhouse environment can be affected by external environmental conditions [13]. To deal with this problem, the use of plant factories with artificial lighting (PFAL) is proposed [14].
PFAL is a high-tech system of controlled environment agriculture where the growing conditions are optimally regulated [15]. The main parts of a plant factory with artificial lighting are a thermally insulated and almost airtight facility, a hydroponic system, suitable lamps to provide artificial lighting, and suitable systems to control temperature, humidity, and air circulation [16]. PFALs are mainly used for vegetable and seedling production as well as for the healing of grafted seedlings [17,18]. Among the vegetables that can be grown in the closed production system are baby leaf vegetables [19].
The growing system can significantly affect parameters related to the yield and quality of the products produced [20]. There are a significant number of comparative studies between different growing systems on the yield and quality of young leaves, but these are limited to different types of greenhouses and also between greenhouse and outdoor cultivation [21,22]. In addition, in recent years, several studies have been carried out concerning the cultivation of leafy vegetables in PFAL, in which the effect of growth conditions on the yield and quality of baby leaves is evaluated [22,23]. However, there is a lack of comparative studies that evaluate the effect of the closed production system in leafy vegetables in combination with resource use efficiency, compared to the greenhouse. To that end, the aim of this study was to evaluate the effect of two systems of controlled conditions, greenhouse and PFAL, on the yield and quality of baby wild rocket leaves as well as water, land, and energy use efficiency. In particular, tests were conducted in two different growing seasons, winter and summer, when environmental conditions are considerably variable and are expected to provoke different responses, mainly in the greenhouse crops.

2. Materials and Methods

2.1. Plant Materials

Baby wild rocket [Diplotaxis tenuifolia (L.) DC.] cv. Torino was cultivated in a glass greenhouse and in a PFAL facility at the Institute of Plant Breeding and Genetic Resources Hellenic Agricultural Organization DIMITRA Thessaloniki (40°32′20.30″ N, 22°59′58.20″ E, 14 m above the sea level). The greenhouse was a single-span pitched type with a metal frame and 4 mm diffusion glass cover, 11.2 m in length, 9.6 m in width, 4.0 m in gutter height, and 5.9 m in ridge height. Two cropping cycles were conducted during January–February (winter) and July–August (summer) in 2020. Sowing was performed in polyester trays of 252 cells (55 × 32 cm) with a substrate of enriched peat. Three seeds were placed in each cell, which was later thinned down to one plant. The trays were placed in darkness immediately after sowing. The air temperature was 22 ± 2 °C (day/night), and relative humidity was 75 ± 5%. At the cotyledon stage, three trays were transferred to a galvanized steel tank in the greenhouse and in the PFAL, respectively. The galvanized steel tanks (59 × 29.5 × 150 cm) were filled with 200 L nutrient solution Hoagland with pH 6.8 and EC = 2.5 mS cm−1. An oxygen enrichment (Resun Air-3000, 180 L/h) and water redistribution (Leo XKF-110P Water Pump, 3700 L h−1) mechanism were installed in both tanks.

2.2. Growing Conditions

In the PFAL, two red–blue light-emitting diodes (LEDs) (GS SLIM SPEC Germination, 120 cm, 45 W) were installed 22 cm above the plants. The photoperiod was set at 14 h, while photosynthetic photon flux density was set at 170 ± 20 µmol m−2 s−1, leading to a mean daily light integral (DLI) of 8.7 mol m−2 d−1. In addition, an air conditioner and humidifier (Rohnson R-9507, 350 mL−1) were installed in order to maintain the temperature and humidity at the desired levels (i.e., 60 ± 5%). Finally, a fan was installed for smooth air circulation and to avoid the creation of suffocating conditions for the plants.
The greenhouse was naturally ventilated through the roof opening. In addition, on the right side of the greenhouse, two fans were placed to achieve air circulation. A heat pump was also installed to maintain the air temperature above 4 °C during the winter.
Both in the greenhouse and the PFAL system, data loggers (HOBO, U12-012) were installed, which recorded the air temperature (Figure 1A,B), the root zone temperature (i.e., in the water tank) (Figure 1C,D), and the daily light integral (DLI) (Figure 1E,F).

2.3. Measurements of Yield and Qualitative Biochemical Characteristics

When the leaf length was 10–12 cm, color, chlorophyll content, and the efficiency of the photosynthetic apparatus were determined, and then all plants were harvested at 2 cm above substrate level in order to measure yield (defined as leaf mass per area; LMA; obtained three samples per treatment), number of leaves (12 plants per treatment), and leaf area.
The leaf area was determined with an AM350 area meter (ADC BioScientific Ltd., Hoddesdon, UK) at 12 plants per treatment. The color was measured with a colorimeter (CR-400 Chroma Meter, Konica Minolta Inc., Tokyo, Japan) at 12 plants per treatment. Color changes were quantified in the L*, a*, and b* color space. Hue angle [(h° = 180° + tan−1 (b*/a*)] and chroma values [C = (a*2 + b*2)1/2] were calculated from a* and b* values. Chlorophyll content was recorded using the CMM-200 portable chlorophyll meter (Opti-Sciences, Hudson, NH, USA) at 12 plants per treatment. The photosynthetic efficiency was evaluated through PIABS (performance index on absorption basis) and ΦP0 (maximum quantum yield of primary photochemistry; also known as Fv/Fm), which were determined using a chlorophyll fluorometer (Hansatech, King’s Lynn, UK) on the outer leaves of 4 plants per replication (12 leaves per treatment).
After harvest, the plants were pulped in a homogenizer. Phytochemical analysis was determined in 3 replications per treatment. The total soluble solid (TSS) content was determined immediately after homogenization from the extract obtained by filtering a small amount of homogenized tissue using an Atago PR-1 refractometer (Atago Co Ltd., Tokyo, Japan) and expressed as g of sucrose per 100 g of solution (°Brix).
The total antioxidant capacity was determined by the ferric reducing antioxidant power (FRAP) method described by Benzie and Strain [24]. Briefly, 3 mL of working solution and 50 µL of the extract for the determination of total soluble phenols or ascorbic acid standard solution were mixed in a test tube. The mixture was incubated in a 37 °C water bath. Exactly 4 min after mixing the reagents, the absorbance of the sample was measured at 593 nm.
The phenolics’ content was determined according to the method described by Singleton and Rossi [25], where plant methanolic extract, sodium carbonate, and Folin-Ciocalteau reagent were mixed. Following this, the absorbance of the incubated solution was measured at 760 nm. A detailed methodology of ascorbate oxidase assay for ascorbic acid quantification is provided by Koukounaras et al. [26].

2.4. Measurements of Resources Use Consumption

Energy Use Efficiency (EUE), Water Use Efficiency (WUE), and Light Use Efficiency (LUE) were measured both on PFAL and greenhouse. The energy use efficiency was calculated based on the energy consumption and yield of rocket expressed by the equation as the ratio between total yield and total electricity consumption [27].
The water use efficiency was expressed as a plant’s fresh weight per total amount of water supplied to the culture tanks and absorbed by plants [27].
The land use efficiency was calculated based on land use and yield of rocket expressed by the equation (kg m−2 a−1) [28]. The yield was calculated considering the cultivation period, leading to the number of cycles per year in two scenarios, featuring a single layer or a vertical layout with four layers.

2.5. Statistical Analysis

The experimental design used was the completely randomized design with SPSS 23.0 (IBM Corp., Armonk, NY, USA). ANOVA, Tukey post hoc analysis, and a t-test (for comparisons within each season) were conducted at p ≤ 0.05.

3. Results and Discussion

Considerable differences were observed regarding the duration of the winter and summer crops, especially in the greenhouse. Specifically, the summer crops had a duration of 32 days in the greenhouse and 33 days in the PFAL. On the contrary, during the winter, the duration of the crop cycle in the greenhouse was 38 days, which was the highest value throughout the experiment and about 27% higher compared to PFAL (33 days). This considerable difference in the length of the crop cycle in winter is attributed to the difference in temperatures that prevailed in the two growing systems, as the mean air temperature in the PFAL was 7 degrees higher than in the greenhouse (Figure 1A,B). This is also in line with Padulosi and Pignone [29], who reported that wild rocket is a cold-season species and shows a reduced crop cycle with higher temperature and day length. In the PFAL system, mean air temperature also remained at similar levels between the seasons, resulting in the stable duration of the crop cycle. The ability of all-year-round cultivation in the PFAL in combination with the optimized duration of production makes it possible to cover the needs of the market throughout the year [30]. Moreover, a root zone temperature of about 22 °C has been reported to benefit the yield of rocket and lettuce in winter and summer conditions compared to uncontrolled temperature in the water tank [31].
When comparing the two crop cycles, no significant differences were observed for baby wild rocket yield performance between the two controlled environment systems. However, in summer, the greenhouse system showed significantly greater LMA compared to PFAL (Figure 2A). Quite similarly, Fraszczak and Knaflewwski [32], in a comparative study they conducted in a growth chamber and a greenhouse in rocket (Eruca sativa), observed a significantly higher yield in the greenhouse. Specifically, the yield increased by 3.35 times in the greenhouse compared to PFAL.
The number of leaves was significantly affected by the growing system (Figure 2B). Specifically, baby wild rocket grown in the PFAL showed a higher number of leaves compared to the greenhouse in both growing seasons. In particular, the number of leaves in PFAL was higher by 10% in winter and 19% in summer. Caruso et al. [33] conducted four crop cycles (April–May, May–June, June–July, and July) and the lowest number of leaves was observed in the July crop cycle. Even in July, where the highest temperatures were observed in combination with higher active photosynthetic radiation, two levels of shading (50% and 79%) resulted in an increase in the number of leaves compared to the control. Similar results also occur in lettuce plants grown in summer months, where shading with four different materials led to a significantly greater number of leaves compared to the control [34]. According to these studies, it seems that there is a mechanism that depends on the light intensity and regulates, among other things, the number of leaves.
Leaf area was 2.3 times higher for baby leaves grown in the PFAL compared to the greenhouse during winter. However, no significant difference was observed for the leaf area during summer (Figure 2C). Low temperatures can lead to a smaller leaf area of wild rocket leaves, which is also confirmed in the work of Guijarro-Real et al. [21]. Specifically, the leaf area was significantly higher in a greenhouse with a heating system compared to outdoor cultivation during winter, while in the spring, no statistically significant differences were reported by the authors. In our case, winter LMA was similar in both systems, but the leaf area was greater in the PFAL. This discrepancy is due to the longer and larger stems of greenhouse leaves that contributed to the final yield but had an insignificant area.
Greenhouse increased the relative chlorophyll content by 27% during winter and 21% during summer (Figure 3A). DLI has been reported to affect chlorophyll concentration. In basil leaves grown in a closed production system under different DLI values, chlorophyll concentration decreased with increasing DLI [35]. Similarly, Baumbauber et al. [36] conducted a study in a closed production system and observed that the concentration of chlorophyll decreased when the DLI increased from 8 to 12 inch kale leaves. However, when the DLI increased to 14 mol m−2 d−1, the highest concentration was recorded. In the same work, spinach and lettuce leaves did not show any significant difference in chlorophyll concentration.
In our study, photosynthetic efficiency was evaluated through chlorophyll fluorescence measurements. φP0, which is one of the most important fluorescence parameters, reflects the maximum photosynthetic capacity of the active PSII system. A higher value of φP0 results in more efficient use of light and greater adaptability of the plant to lower lighting conditions [37]. Under normal conditions, the φP0 value of most C3 species is 0.80–0.84. Values lower than this range can occur when the plant receives some stress, such as drought and high or low temperature but also particularly high or low light levels [38]. Nevertheless, PIABS is considered a more sensitive parameter for the detection of stressful conditions in plants [39]. In particular, summer crops grown in the greenhouse exhibited significant stress compared to the PFAL system, as displayed by PIABS and φP0 values (Figure 3B,C). The stress suffered by wild rocket baby leaves during summer in the greenhouse is clearly depicted by the PIABS values of below 1 unit, as well as by the φP0 values of below 0.70. This may be due to the high intensity of light or the particularly high temperatures that prevailed in this particular season. In winter, greenhouse crops also exhibited significantly lower φP0 values compared to the PFAL counterpart, but leaves showing values of 0.79 are considered as non-stressed since it is very close to the normal value range. Similar results were recorded in the study by Fu and Wu [40] where in lettuce plants grown under different light intensity, the Fv/Fm ratio (i.e., φP0) was lower at high light intensity. In the treatment of 800 µmol m−2s−1 and 600 µmol m−2s−1, the lowest Fv/Fm values were observed, less than 0.80. On the contrary, in the treatments of 200–400 µmol m−2s−1, the value of Fv/Fm was greater than 0.80.
Color is one of the defining criteria for the appearance of rocket leaves. Leaves with an intense and uniform green color gain greater commercial value as they are preferred by consumers [41]. The growing system significantly affected the value of the three-color parameters, L*, C* and Hue, during winter. Specifically, a greater value of the parameters L*, and C*, and lower Hue were observed. Moreover, a significant decrease in the C* and Hue parameters was observed in the greenhouse during summer. However, the L* parameter did not show any significant difference (Table 1).
A higher value of TSS was observed in baby wild rocket grown in the greenhouse in both growing seasons (Table 1). In particular, TSS was 35% and 56% higher in the leaves grown in the greenhouse for the winter and summer crop cycles, respectively. Higher TSS is probably related to osmotic regulation. Under warm or cold conditions, the plants are led to temperature-induced dehydration and, through the increase of TSS, adjust turgor pressure and other physiological functions. Lettuce seedling soluble solids were higher under heat stress. Specifically, 30/25 °C (d/n) resulted in 1.28–1.68 greater TSS concentration among four cultivars compared to 25/20 °C [42]. In another study, eight cultivars of spinach leaves were cultivated in non-heated high tunnels during winter months, and the highest TSS was observed in February when the coldest mean air temperature was recorded [43].
Antioxidant substances, including phenolic compounds and ascorbic acid, are part of the defence mechanism of plants against oxidative stress. In addition, these substances have a beneficial effect on human health [44]. Antioxidant capacity can be significantly affected by growing conditions [45]. However, in this study, the antioxidant content displayed by FRAP, as well as ascorbic acid content, was not significantly affected by the growing system in both growing seasons (Table 1). On the other hand, more phenolic compounds were produced in the PFAL during winter compared to both growing systems in the summer (Table 1). In another study, root zone temperature appears not to play a role in the antioxidant content of rocket and lettuce baby leaves grown in a greenhouse during winter, spring, and summer conditions [31]. The agriculture sector accounts for 70% of fresh water use worldwide and over 40% in Europe [46]. Hatfield et al. [47] report that climate change will affect the water used by crops due to the rise of temperature, increasing CO2 concentration and more variable precipitation. For this reason, the sustainable use of water is necessary. Hydroponic cultivation under controlled environmental conditions enhances water use efficiency compared to traditional cultivation [48]. According to Orsini et al. [49], WUE is higher in PFALs compared to a greenhouse for various leafy vegetables. Indeed, in the current study, the lowest value of water use efficiency was observed in the greenhouse during summer, and it was about 2–2.5 times lower compared to PFAL and greenhouse during the winter crop cycle (Table 2). However, within summer, the growing system did not significantly affect WUE, which is due to the higher yield observed in the greenhouse compared to the PFAL in this season. These results are similar to Schiattone et al. [50], where the WUE was 5 g FW L−1 for the greenhouse rocket. According to Pennisi et al. [51], the cultivation of rocket leaves in a growth chamber with artificial light affected WUE and values reached up to 26 g FW L−1. for baby leaf wild rocket in PFAL under different LED lighting [23].
Energy use efficiency was significantly affected by the growing system in both crop cycles. The energy use efficiency was 8.2 and 17.5 times lower in PFAL, compared to the greenhouse during winter and summer, respectively (Table 2). This is mainly due to the large amount of electric energy needed to maintain the temperature at 22 ± 2 °C during both seasons. The energy consumption was 0.73–0.77 KWh d−1 m−2 for PFAL and 0.08–0.05 KWh d−1 m−2 for greenhouse during winter and summer, respectively. Energy needs are the main challenge for PFAL cultivation. Reducing electric energy has been one of the main objects of research for PFALs and modern greenhouses in recent years [52]. By using renewable energy sources, it is possible to cover a large amount of the energy required for cooling and heating systems as well as artificial lighting [53].
Extreme climate events such as drought and flood will reduce land area suitable for cultivation. Arable land area is likely to decrease by 1–24% depending on the latitude [54]. Controlled environment agriculture is an alternative way to exploit non-arable land areas but also increase land use efficiency [55]. Kozai and Niu [56] reported that among the controlled environment systems, PFAL has the greater LUE. In our study, land use efficiency in the scenario of one layer was not affected by growing system in both seasons (Table 2). However, in PFALs, we have the capability to grow plants in vertical layers and, in this way, to increase the total yield per square meter [57]. In the scenario of four layers, LUE was 4 and 3.8 times higher in PFAL for both crop cycles.

4. Conclusions

The growth cycle was considerably reduced in the PFAL compared to the greenhouse, especially during winter (33 and 38 days, respectively). Vegetative growth was similar within both seasons, but more leaves were developed in the PFAL, irrespective of seasons. On the other hand, quality characteristics such as relative chlorophyll content and total soluble solids were enhanced in the greenhouse, irrespective of seasons. Summer baby leaves grown in the greenhouse were considerably stressed due to the elevated air temperature and daily light integral, as shown by the photosynthetic efficiency evaluations displayed by two stress-sensitive parameters; φP0 and PIABS. Moreover, water use was higher for greenhouse wild rocket during summer. Energy consumption was considerably higher for PFAL during both crop cycles, while land use efficiency can be sharply increased with additional vertical layers. Overall, the growth of wild rocket baby leaves was similar in the PFAL, irrespective of seasons, but with a higher amount of energy consumption. The opposite was evident for greenhouse plants, which were significantly affected by the seasons, which was the same as with water use efficiency. It is necessary to further study the parameters of the controlled environment, such as artificial lighting (quality, intensity, duration), temperature (day/night), humidity, and CO2 concentration in order to find the optimal conditions for growth and development with the addition of study at the molecular level for plant responses.

Author Contributions

Conceptualization, methodology, and data analysis: D.M., F.B. and G.K.N.; experimental measurements: F.B. and D.M.; writing—original draft preparation: D.M. and F.B.; writing—review and editing: G.K.N. and A.K.; supervision and project administration: G.K.N. and A.K. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

Not applicable.

Conflicts of Interest

The authors declare no conflict of interest.

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Horticulturae 09 00661 g001a 550Horticulturae 09 00661 g001b 550
Figure 1. (A,B) Air temperature, (C,D) root zone temperature, and (E,F) daily light integral (DLI) during winter (A,C,E) or summer (B,D,F) cultivation of wild rocket baby leaves grown in a greenhouse (GH; blue lines) or a plant factory with artificial lighting (PFAL; purple lines) system.
Figure 1. (A,B) Air temperature, (C,D) root zone temperature, and (E,F) daily light integral (DLI) during winter (A,C,E) or summer (B,D,F) cultivation of wild rocket baby leaves grown in a greenhouse (GH; blue lines) or a plant factory with artificial lighting (PFAL; purple lines) system.
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Figure 2. (A) Leaf mass per area (LMA), (B) leaf number, and (C) leaf area of wild rocket baby leaves grown in winter (deep red bars) or summer (orange bars) in a greenhouse (GH) or a plant factory with artificial lighting (PFAL) system. Different letters indicate significant differences between all seasons and growing systems (p ≤ 0.05). Asterisks indicate significant differences between growing systems within a season (p ≤ 0.05).
Figure 2. (A) Leaf mass per area (LMA), (B) leaf number, and (C) leaf area of wild rocket baby leaves grown in winter (deep red bars) or summer (orange bars) in a greenhouse (GH) or a plant factory with artificial lighting (PFAL) system. Different letters indicate significant differences between all seasons and growing systems (p ≤ 0.05). Asterisks indicate significant differences between growing systems within a season (p ≤ 0.05).
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Figure 3. (A) Relative chlorophyll content, (B) PIABS, and (C) φP0, of wild rocket baby leaves grown in winter (deep red bars) or summer (orange bars) in a greenhouse (GH) or a plant factory with artificial lighting (PFAL) system. Different letters indicate significant differences between all seasons and growing systems (Tukey post hoc; p ≤ 0.05). Asterisks indicate significant differences between growing systems within a season (t-test; p ≤ 0.05).
Figure 3. (A) Relative chlorophyll content, (B) PIABS, and (C) φP0, of wild rocket baby leaves grown in winter (deep red bars) or summer (orange bars) in a greenhouse (GH) or a plant factory with artificial lighting (PFAL) system. Different letters indicate significant differences between all seasons and growing systems (Tukey post hoc; p ≤ 0.05). Asterisks indicate significant differences between growing systems within a season (t-test; p ≤ 0.05).
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Table
Table 1. Total soluble solids (TSS), ferric reducing antioxidant power (FRAP), phenolic compounds, ascorbic acid content, and colorimetric characteristics of wild rocket baby leaves grown in winter or summer in a greenhouse (GH) or a plant factory with an artificial lighting (PFAL) system. Different letters indicate significant differences between all seasons and growing systems (Tukey post hoc; p ≤ 0.05). Asterisks indicate significant differences between growing systems within a season (t-test; p ≤ 0.05).
Table 1. Total soluble solids (TSS), ferric reducing antioxidant power (FRAP), phenolic compounds, ascorbic acid content, and colorimetric characteristics of wild rocket baby leaves grown in winter or summer in a greenhouse (GH) or a plant factory with an artificial lighting (PFAL) system. Different letters indicate significant differences between all seasons and growing systems (Tukey post hoc; p ≤ 0.05). Asterisks indicate significant differences between growing systems within a season (t-test; p ≤ 0.05).
ParametersWin—GHWin—PFALSum—GHSum—PFAL
TSS (°Brix)6.7 ± 0.1 a ⁎5.0 ± 0.5 b5.3 ± 0.1 b ⁎3.4 ± 0.2 c
FRAP (µg/g f.w.)285.2 ± 10.7 a317.1 ± 40.8 a310.6 ± 19.6 a321.4 ± 9.2 a
Phenolics (mg/g f.w.)1.06 ± 0.3 ab1.19 ± 0.13 a0.84 ± 0.02 bc ⁎0.70 ± 0.02 c
Asc. acid (µg/g f.w.)0.18 ± 0.04 a0.15 ± 0.07 a0.163 ± 0.06 a0.049 ± 0.03 a
Lightness41.9 ± 0.7 a ⁎35.8 ± 0.7 a40.9 ± 4.5 a40.4 ± 0.7 a
Chroma22.5 ± 1.0 b ⁎16.8 ± 0.3 c23.9 ± 0.2 ab26.1 ± 0.8 a ⁎
Hue angle127.1 ± 0.3 b130.6 ± 0.5 a ⁎125.5 ± 0.1 c127.3 ± 0.1 b ⁎
Table
Table 2. Water use efficiency (WUE), energy use efficiency (EUE), and land use efficiency (LUE) of wild rocket baby leaves grown in winter or summer in a greenhouse (GH) or a plant factory with artificial lighting (PFAL) system. Different letters indicate significant differences between all seasons and growing systems (Tukey post hoc; p ≤ 0.05). Asterisks indicate significant differences between growing systems within a season (t-test; p ≤ 0.05).
Table 2. Water use efficiency (WUE), energy use efficiency (EUE), and land use efficiency (LUE) of wild rocket baby leaves grown in winter or summer in a greenhouse (GH) or a plant factory with artificial lighting (PFAL) system. Different letters indicate significant differences between all seasons and growing systems (Tukey post hoc; p ≤ 0.05). Asterisks indicate significant differences between growing systems within a season (t-test; p ≤ 0.05).
ParametersWin—GHWin—PFALSum—GHSum—PFAL
WUE (g f.w./L)10.95 ± 2.01 a13.37 ± 1.75 a5.24 ± 0.92 b8.77 ± 3.10 ab
EUE (g f.w./kWh)228.73 ± 41.87 a ⁎27.77 ± 3.63 b559.01 ± 97.98 a ⁎31.82 ± 11.24 b
LUE (g f.w./m2 d)19.00 ± 3.48 a20.26 ± 2.66 a27.80 ± 4.88 a24.37 ± 8.61 a
* LUE × 4 layers19.00 ± 3.48 b81.04 ± 10.65 a ⁎27.80 ± 4.88 b97.48 ± 34.45 a ⁎
* Indicative land use efficiency in case 4 layers are in operation in the PFAL system.
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Mainos, D.; Bantis, F.; Ntinas, G.K.; Koukounaras, A. Yield, Quality, and Resources Use Efficiency of Wild Rocket Baby Leaves Grown under Different Controlled Environment Systems and Various Growing Seasons. Horticulturae 2023, 9, 661. https://doi.org/10.3390/horticulturae9060661

AMA Style

Mainos D, Bantis F, Ntinas GK, Koukounaras A. Yield, Quality, and Resources Use Efficiency of Wild Rocket Baby Leaves Grown under Different Controlled Environment Systems and Various Growing Seasons. Horticulturae. 2023; 9(6):661. https://doi.org/10.3390/horticulturae9060661

Chicago/Turabian Style

Mainos, Dimitrios, Filippos Bantis, Georgios K. Ntinas, and Athanasios Koukounaras. 2023. "Yield, Quality, and Resources Use Efficiency of Wild Rocket Baby Leaves Grown under Different Controlled Environment Systems and Various Growing Seasons" Horticulturae 9, no. 6: 661. https://doi.org/10.3390/horticulturae9060661

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