The demand for high-quality fresh vegetables and the growing interest of society in the ecological impacts, merge in the need of sustainable production, high nutritional food and obtaining therapeutic active molecules (
Djahida and Houcine, 2021;
Nguyen and Saleh, 2019). In this context, regular consumption of lentils could be enriching the human diet and in order to improve the nutritive value of lentils, growing techniques (including sprouting) have been developed to significantly raise the bioavailability of their nutrients
(Gharachorloo et al., 2012).
The use of light emitting diodes (LEDs) shows sustainable advantages (
Hernandez-Velasco and Mattsson, 2019). LEDs can be customized, enhancing productivity
(He et al., 2019) and raise functional and nutritious characteristics. In several plants blue and red light affect morphogenesis processes like opening of stomata, chlorophyll synthesis, elongation of stem, seed germination and induction to floration among the others
(Lin et al., 2021).
During germination of sprouts, macromolecules are transformed into smaller molecules, increase the digestibility and phytochemistry regular consumption of lentils could be prevent or reduce the development of chronic diseases In order to improve the nutritive value of lentils. The aim of this study was to evaluate the production of functional lentil sprouts produced in indoor farming under different LED light wavelengths.
Plant material and experimental conditions
The present investigation was carried out during 2020 at
Campus Irapuato, Guanajuato University. Lentil seeds of Guanajuato cultivar were soaked in 500 mL with 0.07% sodium hypochlorite for 10 min and then washed with distilled water twice to neutral pH. The hydrated seeds were germinated in paper trays and covered with transparent plastic, germinated at 25°C under blue, violet, green, orange, red at 150 (±10) lx in a dark chamber specially designed for this experiment. As light source panels of 1,645 cm2 with 882 LED SMD5050 RGB with control of light intensity were used. As internal and external controls, groups of seeds were geminated under white and natural (outdoor) light, respectively. Seeds were germinated for 7 days under a photoperiod of 12:12 h. The germination (GE, %) was determined as the percentage of normal seeds. The lengths of the stem (SL, cm) and root (RL, cm) were measured. The biomass (BM, mg) was recorded after drying the plants at 90°C overnight. The relative water content (RWC, %) was determined according to
Ruiz-Nieto et al., (2015). The protein (PT, mg mL
-1) content was evaluated using the protocol described by
Bradford (1976).
Proline (PL, µg mL
-1) was determined using the method described by Bates (1973) measured at 517 nm. β carotene (BCT, µg mL
-1) was determined according to
(Karnjanawipagul et al., 2010) at 461 nm. Phenolic compounds (PHC) (µg mL
-1 gallic acid). was performed according to
(Zin et al., 2006) The Antioxidant activity were determined according to
Martínez-Cruz and Paredes-Lopez (2014). and ABTS according to
(Kuskoski et al., 2005), Chlorophyll a, b and total (mg mL
-1) were determined according to
Dudek et al., (2014) and the equations reported by
Lichtenthaler (1987) and
Lichtenthaler and Buschmann (2001). The data were analyzed using a completely randomized design with five replications, (p<0.05) using the statistical software Minitab
® 16.2.3 (trial version).
Recent studies have proven that the phytochromes modulate endogenous levels of gibberellin (GA) and abscisic acid (ABA), light has an essential role in this physiological process
(Seo et al., 2009). In our results, highly significant differences (p<0.01) were identified in GE. In accordance with
Tufail et al., (2020) GA3 promote the number of leaves and leaf area in plants. In other species like lettuce and buckwheat the green and red wavelengths stimulate the germination
(Zhang et al., 2020; Hayashi et al., 2008).
The SL was strongly affected by white light decreasing 55.81%, green light shows an increase of 31% related the natural light, this could be due skotomorphogenesis which is the evolutionary mechanisms of adaptation to the darkness of plants. In accordance with
Setyaningrum et al., (2020) light intensity affected the fresh weight of plants proportionally. Green light generated stems 2.7 cm longer than natural light and limited the growth as biomass formation (BM, p<0.05). Our results in blue light, are according to Kaydan and Yagmur (2008) which mention that the seedlings with longer root length have more water uptake abilities resulting in a higher RWC.
The higher concentrations of protein were determined with white and violet light with 23.3 and 23.2 mg gdw
-1 (p<0.01) respectively, being the violet light a mix of red and blue wavelength, red and blue light are the two major types of light driving photosynthate biosynthesis
(Bian et al., 2015). Evidence suggests a close relationship between the metabolism of ROS and proline as part of the antioxidant response of plants
(Rejeb et al., 2014), although the excessive production of ROS in plants cause damage to protein, lipids, carbohydrates and DNA
(Govindaraj et al., 2017). Under blue light, lentil sprouts show higher concentrations of β carotene (252 µg mL
-1 gallic acid, p<0.01) and phenolic compounds (670 µg mL
-1 gallic acid, p<0.01), as well as the highest antioxidant activity DPPH (53.2%, p<0.01) and ABTS (7.4%, p<0.01) (Table 1). Regard chlorophyll, the higher concentration was determined under the treatments of blue, violet and orange light (p<0.01). These effects of blue light may be caused by inefficient energy transfer from the carotenoids to the chlorophylls
(Loreto et al., 2009). Chlorophyll a and b are the major light harvesting pigments and sensitive to the wavelengths
(Dutta et al., 2017). In our results, despite of the changes in the concentration of total chlorophyll, no significant differences were identified (p>0.05) in the proportions of chlorophyll a and b with an average of 76.0 and 24.0 % respectively (Fig 1).
