Table 1.
Recent most relevant preharvest UV and visible spectrum lighting as phytochemicals elicitors in sprouts, microgreens, and baby leaves.
| Light Stimuli | Species | Germination Conditions | Light Conditions | Major Findings | Ref. |
|---|---|---|---|---|---|
| Sprouts | |||||
| FL (400–680 nm), B (450 nm), R (660 nm), and FR (730 nm) |
Carrot | 7 d in darkness + 10 d under photoperiod (16 h light/8 h darkness) | FL: 2016 kJ m−2, B + R (25% + 75%): 2073.74 kJ m−2, B + R + FR (22% + 65% + 13%): 2361.8 kJ m−2 |
Phenolic content increased by 45% and 65%, and carotenoid content increased by 279 and 220% after B + R and B + R + FR, respectively. | [56] |
| UV-B (280–320 nm) |
Red cabbage | 10 d in darkness + UVB on days 3, 5, 7, and 10 | UVB5: 1.25 kJ m−2 d−1, UVB10: 2.50 kJ m−2 d−1, UVB15: 3.25 kJ m−2 d−1 | UVB15 induced the highest carotenoid content and total antioxidant capacity. Total flavonoid content was increased by 35 and 30% under UVB10 after 10 d at 4 °C. | [57] |
| UV-B (280–320 nm) |
Kale | 10 d in darkness + UVB on days 3, 5, 7, and 10 | UVB5: 1.25 kJ m−2 d−1, UVB10: 2.50 kJ m−2 d−1, UVB15: 3.25 kJ m−2 d−1 | Hydroxycinnamic acid content was increased by 52% and glucoraphanin by 36% after UVB15, even after 10 d at 4 °C. | [11] |
| W (380 nm), B (470 nm), R (660 nm), and B + R |
Canola | 14 d at 25 °C under photoperiod (16 h light/8 h darkness) | PPFD: 50 µmol m−2 s−1 |
The highest total phenolics under B light. R light increased the sprout growth. | [52] |
| UV-A (365), B (450 nm), R (660 nm), and combinations |
Broccoli | 36 h in darkness + 5 d photoperiod (16 h light/8 h darkness) 23 °C and 77% RH | PPFD: 50 µmol m−2 s−1 for B, R, R + B (50 + 50%), and R + UVA (50 + 50%) | B and R + B estimulated cotyledon metabolite increased total phenolic content, total flavonoid content, and glucoraphanin content. | [54] |
| B (465 nm), R (650–670 nm), and W (400–700 nm) |
Wheat | 10 d under photoperiod (16 h light/8 h darkness) 23 °C and 70% RH | PPFD: up to 264 µmol s−1 for R, 201 µmol s−1 for W, 263 µmol s−1 for B |
A PPFD of 82 µmol s−1 was enough to achieve the maximun leaf parameters. | [51] |
| FL, B (460 nm), and R (625 nm) |
Buckwheat | 2 d in darkness + 7 d under photoperiod (16 h light/8 h darkness) at 25 °C | PPFD: 35 µmol s−1 | B light increased total phenolics, total flavonoid content, and antioxidant capacity. | [50] |
| W (400–700 nm), B (440 nm), G (545 nm), Y (580 nm), and R (610 nm) |
Soybean, mung bean, radish, and pumpkin | 5 d under photoperiod (16 h light/8 h darkness) 24 °C and 78% RH | PPFD: 110 µmol s−1 | R light in soybean sprouts increased total phenolics and W, R, and B light preserved vitamin C, carotenoid, chlorophyll, and anthocyanin content in all sprouts. | [55] |
| W and combinations of B (460 nm) and R (640 nm) | Chinese kale | 1 d at 28 °C + 9 d under photoperiods (0–16 h light/24–8 h darkness) 25 °C and 78% RH |
PPFD: 150 µmol s−1 for W and combinations of B + R (10 + 0%, 8 + 2%, 5 + 5%, 2 + 8%, and 0 + 10%) | B + R (10 + 0%) light increased glucosinolates. | [58] |
| UV-B (300 nm), B (450 nm), and G (510 nm) |
Kale, rocket, and kohlrabi | 3 d + 8 d under photoperiod (12 h light/12 h darkness) at 20 °C | PPFD: B 99 µmol m−2 s−1 or G 119 µmol m−2 s−1, + UV-B 1.15 kJ m−2 |
B enhanced concentrations of flavonoid glycosides, but G did not. B + UV-B increased singlet oxygen scavenging. | [59] |
| W (400–700 nm) | Broccoli, red radish, red cabbage, and white mustard | 3 d + 4 d under photoperiod (18 h light/6 h darkness) at 20 °C | PPFD: 230 µmol m−2 s−1 | Increase of glucosinolates in all the species studied. | [53] |
| Microgreens | |||||
| Combination of B (445 nm), R1 (638 nm), R2 (665 nm), and FR (735 nm) |
Kohlrabi, mustard, red pak choi, and tatsoi | 10 d under photoperiod (16 h light at 21 °C/8 h darkness at 17 °C) and 50–60% RH | PPFD: 110–545 µmol m−2 s−1 B (7.5%), R1 (41.3%), R2 (50.3%); FR (0.9) |
320–440 umol m−2 s−1 Larger leaf and higher total anthocyanins, total phenols, and DPPH scavenging capacity. |
[60] |
| - | Broccoli, kale, Tronchuda cabbage, and red cabbage | 12 d at 25 °C under photoperiod (16 h light/8 h darkness) | - | Higher glucosinolate content under photoperiod. | [61] |
| Fl (400–680 nm) and combinations of B (465 nm), R (669 nm), and FR (730 nm) | Purslane | 3 weeks at 25–20 °C and 80% RH under photoperiod (16 h light/8 h darkness) | PPFD: 150 ± 5 µmol m−2 s−1 Fl: 24 h and R + B ratio of 0.74, B + R (25% + 75%; ratio 3), B + R + FR (22% + 65% + 13%; B + R + 15%FR) |
Nitrate content was reduced by 81 and 91% under B + R and B + R + FR, respectively. The lowest oxalate content with B + R and B + R + FR. The highest total phenolic content under B + R. |
[62] |
| B (447 nm), G (520 nm), Y (595 nm), O (622 nm), R1 (638 nm), R2 (665 nm), and FR (731 nm) | Mustard, red pak choi, and tatsoi | 10 d at 21/17 °C and 50–60% RH under photoperiod (16 h light/8 h darkness) | PPFD: 300 µmol m−2 s−1 B + R1 + R2 + FR supplemented with 5% of G, Y, and O |
G, Y, and O supplemental wavelengths increased total carotenoids in mustard but decreased it in red pak choi. Carotenoid content increased in tatsoi under supplemental Y light. |
[63] |
| Combinations of B (447 nm) and R (660 nm) | Mustard and kale | 5 d at 21/17 °C and 60% RH under photoperiod (18 h light/6 h darkness) | PPFD: 250 µmol m−2 s−1 B + R at 0 + 100%, 10 + 90%, 25 + 75%, 50 + 50%, 75 + 25%, and 100 + 0% |
25 and 50% of B sufficiently induced high yields and levels of mineral nutrients. | [64] |
| Combinations of B (400–499 nm) and R (600–699 nm) | Brassica | 6–12 d under lighting |
PPFD: 150 µmol m−2 s−1 B + R at 20 + 80% and 80 + 20% and B + G + R at 20 + 10 + 70% and 70 + 10 + 20% |
B + G + R at 20 + 10 + 70% showed a positive influence on the growth and morphology of microgreens. | [65] |
| B1 (455 nm), B2 (470 nm), B3 (505 nm), Y (590 nm), and R (627 nm) | Red pak choi and tatsoi | 7 d at 21/17 °C and 55% RH under photoperiod (16 h light/8 h darkness) | PPFD: 200 µmol m−2 s−1 Pulsed light frequencies at 2, 32, 256, and 1024 Hz with cycle of 50% |
High total phenolic content in mustard under all wavelength LEDs at 2, 256, and 1024 Hz. High anthocyanins in red pak choi and tatsoi with 2 and 32 Hz. The highest antioxidant activity in mustard with 32, 256, and 1024 Hz and in red pak choi and tatsoi with 2 Hz. |
[66] |
| Combinations of B (447 nm), G (520 nm), Y (595 nm), O (622 nm), R1 (638 nm), R2 (665 nm), and FR (731 nm) | Mizuna, broccoli, and kohlrabi | 10 d at 21/17 °C and 50–60% RH under photoperiod (16 h light/8 h darkness) | PPFD: 300 µmol m−2 s−1 B + R1 + R2 + FR (14 + 35 + 50 + 1%), B + R1 + R2 + FR (14 + 30 + 50 + 1%) + 5% of G, Y, and O |
Y light increased the soluble carbohydrate content and O light increased Fe, Mg, and Ca content in all microgreens. All supplemented lights increased β-carotene in mizuna and ascorbic acid in kohlrabi. |
[67] |
| Combinations B (455 nm), Y (590 nm), and R (660 nm) | Mizuma, pak choi, radish, and mustard | 2–3 d under photoperiod (16 h light/ 8 h darkness) at 24 °C and 90% HR + 13–14 d under the same photoperiod at 16 °C and 70% RH | PPFD: 179–197 µmol m−2 s−1 of B (20.5–58.9%) + Y (4.7–39.5%) + R (74.4–0.6%) | High antioxidant activity (DPPH), total phenolic content, and total flavonoid content increased in glucosinolates. | [68,69] |
| Combinations of B (445 nm), R1 (638 nm), R2 (665 nm), and FR (731 nm) | Mustard, beet, and parsley | 13 d at 21/17 °C and 50–60% HR under photoperiod (16 h light/ 8 h darkness) | PPFD: 300 µmol m−2 s−1 R1 + R2 + FR (43 + 56.2 + 0.8%) + B(0–33%) |
33% of B light increased chlorophylls a and b, carotenoids, α- and β-carotenes, lutein, violaxanthin, and zeathin content from 1.2- to 4.3-fold. Tocopherols were increased by 1.3-fold with 16% of B light. |
[70] |
| Baby Leaves | |||||
| Combination of B (455 nm), R1 (627 nm), R2 (660 nm), and FR (735 nm) | Green- and red-leaf lettuce | 27 d at 22/18 °C and 60–70% RH under photoperiod (18 h light/6 h darkness) | PPFD: 100–500 µmol m−2 s−1 (2% FR, 10% B, 44% R1, and 44% R2) |
Adequate growth and lower nitrate and nitrite contents with a PPFD 300–400 µmol m−2 s−1. | [71] |
| B (455 nm), R1 (627 nm), R2 (660 nm), and FR (735 nm) | Green- and red-leaf lettuce | 25 d under different photoperiods at 22/18 °C and 60–70% RH | Photoperiod: 12–24 h of light with a PPFD of 300 µmol m−2 s−1 (2% FR, 10% B, 44% R1, and 44% R2) |
Adequate growth and lower nitrate and nitrite contents with a photoperiod of 16–18 h of light. | [71] |
| W supplemented with UV-A | Chinese kale | 14 d at 24 °C and 65–75% RH under photoperiod (10 h light/14 h darkness) + 10 d in photoperiod (12 h) of UV-A (0–15 W m−2) | W PPFD: 300 µmol m−2 s−1 UV-A PPFD: 0–30 µmol m−2 s−1 |
10 W m−2 UV-A improved the plant biomass and morphology, and increased antioxidant compounds. 15 W m−2 UV-A increased glucosinolate content. |
[72] |
| B1 (430 nm), B2 (465 nm), UV-A1 (380 nm), UV-A2 (400 nm) | Chinese kale and pak choi | 10 d under photoperiod with natural light (35 °C/20 °C; day/night) and 35–90% HR + 10 d in sampe photoperiod supplemented with 12 h of B and UV-A | Natural light PPFD: 400–1000 µmol m−2 s−1. B and UV-A intensity: 40 W m−2 |
B supplementation resulted in higher biomass, better morphological traits, and higher antioxidant compounds. UV-A supplementation enhanced glucosinolate content. |
[73] |
| W (380–780 nm) |
Lettuce sprouts, microgreens, and baby leaves | 50 d at 20 °C under photoperiod with 16/8 h (day/night) | PPFD: 107–150 μmol m− 2 s−1 | Lettuce cv. Romana under LED provided 648.44 and 833.71% of the total daily intake required of vitamin A. There was an inverse relationship between nitrate and carotenoid contents. | [74] |
| W, B (468 nm), R (629 nm), G (524 nm) |
Spinach | 26 d under photoperiod with natural light | PPFD: 26.0 μmol m−2 s−1 | R stimulated biomass production and G and B increased total phenolic content and antioxidant capacity. | [75] |
| Combinations: UV (380–399 nm), B (400–499 nm), G (500–599 nm), R (600–699 nm), and FR (700–780 nm) | Spinach | 28 d at 22 °C under photoperiod with 16/8 h (day/night) | PPFD: 150 μmol m−2 s−1 | Plants were better developed when they were treated with high proportions of R, either with FR and low B or with balanced B, G, and FR. | [76] |
| W (380–780 nm) supplemented with R, B, and Gray | Spinach | 26 d under photoperiod with natural light and covered by colour nettings | PPFD: R 118.4 μmol m−2 s−1, B 118 μmol m−2 s−1, Gray 63.18 μmol m−2 s−1 | The total phenolics and the antioxidant capacity were higher under R, which was also maintained after 10 d at 4 °C. | [77] |
| Warm W (400–780 nm; peak 639 nm) supplemented UV-A (385 nm), B (449 nm), G (526 nm), R (664 nm) |
Lettuce | 17 d at 22 °C under photoperiod with 18/6 h | PPFD: 200 μmol m−2 s−1 WarmW + 30 μmol m−2 s−1 UV-A or 50 μmol m−2 s−1 B, G, or R | UV-A and B increased the accumulation of secondary metabolites at harvest and R preserved them after 7 d at 5 °C. | [78] |
| UV-C (280 nm) |
Spinach | 27 d at 22 °C under photoperiod with 14/8 h natural light | UV-C intensity: 1.5 kJ m−2 and 3 kJ m−2 | UV-C supplementation resulted in higher total phenolic content, antioxidant capacity, and lower mesophilic load, also maintained after 6 d at 5 °C. | [79] |
| UV-C (280 nm) |
Spinach, whose seeds were inoculated with Alternaria alternata | 29 d at 22 °C under photoperiod with 14/8 h natural light | UV-C intensity: 0.3, 0.6, and 0.9 kJ m−2 × 2 or 5 times | The lower UV-C treatment showed the highest vitamin C content and FRAP antioxidant capacity. The highest UV-C dose reduced the yeast counts. | [80] |
UV-A: ultraviolet-A; UV-B: ultraviolet-B; UV-C: ultraviolet-C; FL: fluorescent lights; B: blue LED; G: green LED; Y: yellow LED; R: red LED; FR: far-red LED; W: white LED; PPFD: Photosynthetic Photon Flux Density.