Growth Of Leaf Lettuce Research Articles

Combined Effects of Different LED Light Recipes and Slow-Release Fertilizers on Baby Leaf Lettuce Growth for Vertical Farming: Modeling through DoE

The modern agriculture system based on open-field crops requires a lot of energy and resources in terms of soil, water, and chemicals. Vertical farming (VF) systems could be a viable alternative for some types of cultivation that are receiving interest thanks to their high modularity, optimized water and nutrients use, and LEDs employment as an energy-efficient light source. However, VF design and installation are expensive and require well-tailored optimization depending on the specific crop to increase its competitiveness. This work analyzed the effects of different combinations of NPK (nitrogen-phosphorus-potassium) slow-release fertilizers and LED-based light recipes on the growth of baby leaf lettuce (Lactuca sativa L.), taking advantage of the Design of Experiments (DoE) methodology. The type of slow-release fertilizer, its quantity measured as the number of aggregates from 0 to 6, and the type of light recipe were considered as input factors, and their possible influence on the growth of lettuce (in terms of morphological parameters) in a controlled indoor farming system was measured. Results suggest that using higher fertilizer inputs equal to six aggregates leads to an increase of average leaf area equal to 46% (from 13.00 cm2 to 19.00 cm2), while the fresh weight of lettuce increases by 65% (from 1.79 g to 2.96 g). However, the height of plants also depends on the combination of the light recipes. In particular, the separate coupling of higher inputs of two fertilizers and light recipes leads to an increase in the height of lettuce equal to 33% (from 6.00 cm to 8.00 cm).

GA signaling protein LsRGL1 interacts with the abscisic acid signaling-related gene LsWRKY70 to affect the bolting of leaf lettuce.

A variety of endogenous hormone signals, developmental cues, and environmental stressors can trigger and promote leaf lettuce bolting. One such factor is gibberellin (GA), which has been linked to bolting. However, the signaling pathways and the mechanisms that regulate the process have not been discussed in full detail. To clarify the potential role of GAs in leaf lettuce, significant enrichment of GA pathway genes was found by RNA-seq, among which the LsRGL1 gene was considered significant. Upon overexpression of LsRGL1, a noticeable inhibition of leaf lettuce bolting was observed, whereas its knockdown by RNA interference led to an increase in bolting. In situ hybridization analysis indicated a significant accumulation of LsRGL1 in the stem tip cells of overexpressing plants. Leaf lettuce plants stably expressing LsRGL1 were examined concerning differentially expressed genes through RNA-seq analysis, and the data indicated enhanced enrichment of these genes in the 'plant hormone signal transduction' and 'phenylpropanoid biosynthesis' pathways. Additionally, significant changes in LsWRKY70 gene expression were identified in COG (Clusters of Orthologous Groups) functional classification. The results of yeast one-hybrid, β-glucuronidase (GUS), and biolayer interferometry (BLI) experiments showed that LsRGL1 proteins directly bind to the LsWRKY70 promoter. Silencing LsWRKY70 by virus-induced gene silencing (VIGS) can delay bolting, regulate the expression of endogenous hormones, abscisic acid (ABA)-linked genes, and flowering genes, and improve the nutritional quality of leaf lettuce. These results strongly associate the positive regulation of bolting with LsWRKY70 by identifying its vital functions in the GA-mediated signaling pathway. The data obtained in this research are invaluable for further experiments concerning the development and growth of leaf lettuce.

Effects of Time Variation of Light Intensity on the Growth of the Leaf Lettuce “Greenwave”

The growth and morphogenesis of leaf lettuce in response to gradual changes in light intensity over time were investigated. Seedlings of leaf lettuce (Lactuca sativa L. var. crispa “Greenwave”) were grown in a blue to red light-emitting diode (LED) ratio of 0.33 and daily light integral (DLI) of 8.7 mol m-2 d-1. The first experiment was conducted with nine treatments, in which light intensity varied every 15 min with its peak during the day and a consistent dark period of 8 h. In the second experiment, three dark period lengths and three irradiation changes were combined based on the irradiations that produced different plant growth responses in the first experiment. Based on the results of the two experiments, most of the irradiation methods with the same DLI and dark period resulted in similar leaf lettuce growth in terms of plant weight and shape. However, plant weight was reduced when a high level of light intensity was employed for a long duration during the light period. Shorter dark periods can accelerate the growth of leaf lettuce. Consequently, the results from this study propose a new irradiation method with a non-constant light intensity in relation to time.

Leaf lettuce (Lactuca sativa L. ‘L-121’) growth in hydroponics with different nutrient solutions used to generate ultrafine bubbles

Fine bubble (FB) and ultrafine bubble (UFB) generators have been installed in hydroponic systems to promote plant growth. However, their application is limited because the mechanism of the effect of UFBs is not well understood. We aimed to evaluate the effect of UFBs on promoting leaf lettuce growth in hydroponics using nutrient solutions prepared with tap water (Control) and two UFB water—tap water (standard, STD) and calcium nitrate solution (original, ORL). We then compared the differences among the three treatments under the same nutrient concentration and environmental conditions. The shoot fresh weights, dry weights, nutrient element (Zn, K, Mn, Fe, Cu, Ca, and Mg) concentrations, and total nutrient element quantity were measured after harvesting. The shoot fresh and dry weights were higher in the STD and ORL treatments than in the control, but no difference was noted between the STD and ORL treatments. Plant nutrient element uptake was higher in the STD and ORL treatments than in the Control treatment. Additionally, Mn uptake differed between the STD and ORL treatments. The results indicated that plant growth promotion in the STD and ORL treatments was affected by reactive oxygen species generated by UFBs. UFB properties also allowed for the supply of sufficient nutrients enabling rapid growth. Furthermore, we suggest that the type of solution used altered the properties of the FBs and UFBs, which in turn influenced the uptake of nutrients by the plants.

The Growth of Leaf Lettuce and Bacterial Communities in a Closed Aquaponics System with Catfish

Aquaponics is a circulating and sustainable system that combines aquaculture and hydroponics and forms a symbiotic relationship between fish, plants, and microorganisms. We hypothesized that feed alone could support plant growth, but the symbiosis with fish adds some beneficial effects on plant growth in aquaponics. In this study, we created three closed culture systems, namely, aquaponics, hydroponics without nitrogen (N) and phosphorus (P), and aquaculture, and added the same amount of feed containing N and P to all the treatments in order to test the hypothesis. Accumulation of NO3− and PO43− was alleviated in aquaponics and hydroponics as a result of plant uptake. Lettuce plants grown in aquaponics grew vigorously until 2 weeks and contained a constant level of N in plants throughout the production period, whereas those in hydroponics grew slowly in the early stage and then vigorously after 2 weeks with a late increment of N concentration. These results suggest that catfish help with the faster decomposition of the feed, but, in hydroponics, feed can be slowly dissolved and decomposed owing to the absence of the fish. The bacterial community structures of the culture solution were investigated using 16S rRNA gene amplicon sequencing. At the class level, Actinobacteria, Alphaproteobacteria, Betaproteobacteria, and Gammaproteobacteria were the major microbial groups in the solutions. Aquaponics prevented the pollution of tank solution and maintained a higher water quality compared with hydroponics and aquaculture, suggesting that aquaponics is a more sustainable cultivation system even in a small-scale system.

Effect of organic fertilizer mixed with dehydrated food waste powder on growth of leaf lettuce

Effect of organic fertilizer mixed with dehydrated food waste powder on growth of leaf lettuce

Erratum: Interactive Effects of Photoperiod and Nitrogen Form on the Growth of Leaf Lettuce and Fluctuation of Nutrient Solution pH in Plant Factory Condition [Shokubutsu Kankyo Kogaku Vol. 32 (2020) No. 3 P 143–152

Erratum: Interactive Effects of Photoperiod and Nitrogen Form on the Growth of Leaf Lettuce and Fluctuation of Nutrient Solution pH in Plant Factory Condition [Shokubutsu Kankyo Kogaku Vol. 32 (2020) No. 3 P 143–152

Time-varying Photosynthetic Photon Flux Density and Relative Spectral Photon Flux Density Distribution to Improve Plant Growth and Morphology in Plant Factories with Artificial Lighting

In contrast to fluorescent lamps and high-power sodium lamps, the use of light-emitting diode (LED) lamps enables the control of not only photosynthetic photon flux density (PPFD) at the plant level, but also the relative spectral photon flux density distribution (RSPD) of light because of the variety, even at different times of day, of producible light emitted by LEDs of different types. Effects of the spectral photon flux density on plant growth and morphology have been investigated using several types of LEDs and plant species. However, few studies on lighting methods with time-varying PPFD or RSPD have been published to date. In this paper, we summarize the effects of time-varying PPFD on the net photosynthetic rate (Pn) and those of time-varying RSPD on plant growth and morphology. Detailed modeling studies have been conducted on the reactions of the photosynthetic pathway under time-varying PPFD at a cycle of milliseconds to seconds. The results of these modeling studies and actual measurements of Pn under pulsed light clearly indicate that pulsed light is not advantageous to improve Pn. Although the integrated PPFD of blue and red light was unchanged, the growth of leaf lettuce was promoted by asynchronous irradiation with blue light and red light compared with growth under simultaneous irradiation. We think that blue-light monochromatic irradiation promotes leaf elongation through leaf expansion as a primary factor in the enhancement of plant growth. In addition, changes in leaf photosynthetic capacity caused by blue-light monochromatic irradiation may be involved in plant growth promotion. An increasing number of studies have investigated the effects of time-varying RSPD on plants. However, the mechanisms underlying these effects remain to be elucidated.

Effect of alternating red and blue irradiation on the growth of leaf lettuce

Effect of alternating red and blue irradiation on the growth of leaf lettuce

Application of Directly Brewed Compost Extract Improves Yield and Quality in Baby Leaf Lettuce Grown Hydroponically

The aim of this work was to study whether the application of a directly brewed compost extract (added in the nutrient solution or by microsprinkler) could be used to improve the yield and quality of baby leaf red lettuce growing in a floating system, and to control the incidence of Pythium irregulare. Its effect on the quality of fresh-cut red lettuce was also studied. For this, two experiments were carried out over two growing cycles (winter–spring and autumn). The results showed that the use of compost extract added to the nutrient solution improved baby leaf lettuce growth and quality, reducing the nitrate content and enhancing the content of potentially health-promoting compounds such as phenols and flavonoids and the antioxidant capacity. Microbial quality was maintained during storage and the compost extract had no negative effect on the microbial load of the final product. In addition, application of the compost decreased the population of P. irregulare in the water. It is concluded that the application of directly brewed compost extract is of potential use in a sustainable soilless production system for baby leaf red lettuce, since it improves the yield and quality of the product and is able to control the incidence of P. irregulare.

Growth response of hydroponic leaf lettuce and komatsuna to ozone microbubble treatment

Previously, we found that ozone microbubble (O3MB) treatments of 0.2 mg L−1 of dissolved ozone (DO3) are effective for sterilizing hydroponic solutions. However, there are few studies on cultivated plant growth responses to O3MB-treated hydroponic solutions. We investigated effects of different O3MB treatments in hydroponic solutions on the growth of leaf lettuce and komatsuna plants, and inhibiting factors for komatsuna growth. Fe concentrations in O3MB-treated hydroponic solutions decreased significantly compared with control solutions because of the precipitation of oxidized Fe. The growth of hydroponic lettuce treated with O3MB was equivalent to that of the control. However, the growth of komatsuna was suppressed with increasing DO3 concentrations. Leaf lettuce might avoid Fe deficiency by secreting riboflavin from roots. On the other hand, since komatsuna does not secrete riboflavin against Fe deficiency, Fe deficiency in hydroponic solutions might lead to growth suppression. We investigated the influence of added Fe in hydroponic solutions treated with O3MB on the growth of komatsuna. No growth differences for komatsuna were observed between Fe-added hydroponic solutions treated with O3MB and the control solution. Growth suppression of O3MB-treated hydroponic komatsuna may be avoidable by Fe addition.

Interactive Effects of Photoperiod and Nitrogen Form on the Growth of Leaf Lettuce and Fluctuation of Nutrient Solution pH in Plant Factory Condition

Interactive Effects of Photoperiod and Nitrogen Form on the Growth of Leaf Lettuce and Fluctuation of Nutrient Solution pH in Plant Factory Condition

Photoresponse to different lighting strategies during red leaf lettuce growth

The objective of the study was to investigate the effects of growth-stage specific lighting for the physiological homeostasis of red leaf lettuce (Lactuca sativa L. cv. Red Cos), by measuring the productivity of photosynthesis and primary metabolism. In the experiments, the main photosynthetic photon flux consisted of red (R) and blue (B) light, supplemented with blue, green (G) or UV-A wavelengths. Decrease of fructose, accompanied by significant decrease of stomatal conductance (gs), the ratio of intracellular to ambient CO2 concentration (Ci/Ca), photosynthetic rate (Pr), light adapted actual quantum yield of PSII photochemistry (ΦPSII), biomass formation and significant increase of transpiration rate (Tr) suggest that supplemental UV-A during maturity stage, after supplemental green irradiation during seedling stage (BRG to BRUV) was the least favourable condition for red leaf lettuce. However, constant irradiation with supplemental green (BRG) or supplemental green irradiation after increased blue exposure (B↑R to BRG) resulted in significant increase of Pr, gs, Ci/Ca, and light use efficiency(LUE), and decrease of Tr and Water use efficiency (WUE). Significant increase of leaf area was observed under supplemental green in both seedlings (BR; BRG) and matured plants (B↑R to BRG). Significant increase of specific leaf area was found under supplemental green (BRG) for seedlings and under increased blue (B↑R) for matured plants. Accordingly, the most favourable growth-stage specific lighting spectrum strategy for red leaf lettuce, based on photosynthetic and primary metabolite response, is supplemental green irradiation after increased blue exposure (B↑R to BRG), whereas, the most favourable condition for seedlings is BRG. According to the PCA correlation matrix, associations among the measured data indicate that WUE negatively correlated with gs and Ci/Ca, while LUE positively correlated with gs and Pr. However, weak correlations between ФPSII, LUE and photochemical reflectance index (PRI) suggest that selected light conditions were not optimal for red leaf lettuce.

LED Energy Consumption and Leaf Lettuce Growth Using Small Indoor Hydroponic System

LED Energy Consumption and Leaf Lettuce Growth Using Small Indoor Hydroponic System

Growth control of leaf lettuce with exposure to underwater ultrasound and dissolved oxygen supersaturation

The growth rate of vegetables in plant factories can be regulated by environmental factors including light, temperature, and chemicals, which might give rise to mutation in leaf health. Here, we aim to devise a new way that allows for controlling the growth rate of plants in hydroponics as well as maintaining the product quality; we apply underwater ultrasound and dissolved oxygen supersaturation as external stimuli to plants. As an example, we examine the growth of leaf lettuce in hydroponics with exposure to 28-kHz ultrasound and dissolved oxygen supersaturation up to 36 mg/L at 20 °C. Our results show that exposure to the ultrasound of peak-to-peak pressure at 20 kPa or larger works as the growth inhibitor of the leaves and the roots, while the oxygen supersaturation as the growth promoter, without any degradation of chlorophyll in the leaves. This suggests that these external stimuli can be used in the growth control system of plant factories.

Effect of green, yellow and purple radiation on biomass, photosynthesis, morphology and soluble sugar content of leafy lettuce via spectral wavebands “knock out”

Abstract Spectral composition of artificial light is an important environmental factor for plants cultivated in controllable environment, eg., plant factory. In an attempt to explore the influence of different spectral wavebands on leaf lettuce growth and development, a new way of light treatment with turning off the specific narrow-wavebands from the wide spectrum was established. And leaf lettuce was cultivated under different light spectra with the spectral wavebands of green (LG), yellow (LY) and purple (LP) “knockout” respectively in controllable environment. Then changes in biomass, morphological indexes, photosynthetic gas exchange, chlorophyll content and soluble sugar content of lettuce were examined. Our results revealed that, compared with plants grown under wide-spectral LED light (CK), LG treatment showed significantly reduction of fresh shoot weight at 25 days after planting (DAP) comparing to CK. LY and LP obtained obviously higher fresh shoot weight and moisture content at 15 DAP, in contrast, significantly lower ratio of root to shoot than CK. And A/Ci in LG were significantly reduced by about 33.3% and 36.1% at 20 DAP and 25 DAP respectively compared with CK. In addition, LY showed significant increases in soluble sugar content compared to other treatments at three sampling stages, while the lowest values were obtained in CK. These results indicated that green, yellow and purple light had significant regulations on the biomass, photosynthesis and soluble sugar content in lettuce, depending on the different growth period.

Impact of Low and Moderate Salinity Water on Plant Performance of Leafy Vegetables in a Recirculating NFT System

Two greenhouse experiments were conducted to examine the growth and mineral nutrition of four leafy vegetables in a nutrient film technique (NFT) system with water with low to moderate salinity. In Expt. 1, a nutrient solution was prepared using reverse osmosis (RO) water and treatments consisted of supplementing with RO water, tap water, or nutrient solution. In Expt. 2, nutrient solution was prepared using three different water sources (treatments), namely, RO water, tap water, or tap water, plus sodium chloride (NaCl), and supplementing solution was prepared using the same three water sources at one third strength. For both of the experiments, seeds of pac choi ‘Tokyo Bekana’, ‘Mei Qing Choi’, and ‘Rosie’ (Brassica rapa var. chinensis) and leaf lettuce ‘Tropicana’ (Lactuca sativa) were sown and were grown in a growth chamber. Two weeks after sowing, seedlings were transplanted to the NFT systems. Expt. 1 was conducted from 19 April to 19 May 2016 and Expt. 2 from 6 September to 12 October 2016. In Expt. 1, nitrate (NO3−) and phosphorus (P) levels in the tanks decreased, and potassium (K+) levels reached almost zero at the end of the experiment when supplemented with RO or tap water. However, calcium (Ca2+), magnesium (Mg2+), and sulfate (SO42−) either did not decrease or increased over time. Supplementing water type did not affect the growth of leaf lettuce and ‘Mei Qing Choi’ pac choi; however, fresh weight of ‘Rosie’ pac choi and both fresh and dry weight of ‘Tokyo Bekana’ pac choi were reduced when supplemented with RO water. Leaf sap NO3− was reduced in ‘Tokyo Bekana’ pac choi, but not in other varieties, when supplemented with RO or tap water. Leaf sap K+ decreased in ‘Tokyo Bekana’, but not in other varieties. The supplementing water type did not impact leaf sap Ca2+, regardless of vegetable varieties. In Expt. 2, NO3− in all of the treatments, P in RO water, and K+ in RO or tap water decreased in the last week of the experiment. Other macronutrients did not change substantially over time. The addition of NaCl significantly reduced the growth of all the vegetables. ‘Tropicana’ leaf lettuce was the least tolerant to NaCl, followed by ‘Rosie’ pac choi. Water source did not affect leaf Ca2+, K+, P, SO42−, and Mg2+ except for ‘Tokyo Bekana’ where NaCl addition decreased Ca2+ and Mg2+. Our results indicated that the tested leafy vegetables differed in response to various types of water used as supplementing or as source water. N, P, and especially K, should be supplemented in the late stage of the experiment, while replacing the whole tank nutrient solution is only necessary when Na+ and/Cl− build up to harmful levels.

Effects of Oxidative stress on the Growth of Leaf Lettuce upon H2O2 Treatment

Effects of Oxidative stress on the Growth of Leaf Lettuce upon H2O2 Treatment

Effects of Irradiation Patterns and Light Quality of Red and Blue Light-Emitting Diodes on Growth of Leaf Lettuce (<I>Lactuca sativa</I> L.“Greenwave”)

Effects of Irradiation Patterns and Light Quality of Red and Blue Light-Emitting Diodes on Growth of Leaf Lettuce (<I>Lactuca sativa</I> L.“Greenwave”)

Growth Control of Leaf Lettuce Using Pulsed Electric Field

Agriculture in Japan is approaching a crisis for two reasons: a declining self-sufficiency rate and a decreasing number of agriculture workers. To solve these problems, plant factories have been attracting attention recently. Plant factories are facilities that aid the steady production of high-quality vegetables year round by artificially controlling the cultivation environment, allowing growers to drastically decrease production time. Despite the many advantages of plant factories, a main impediment is the reduction of initial and running costs. This paper utilizes leaf lettuce (Early impulse), which is a typical item cultivated in plant factories, as a target to improve productive efficiency of plant factories due to its relatively high price. Various pulsed electric fields (PEFs) were applied to roots of the lettuce to increase lettuce growth rate. The experimental results show PEF intensity from 0.2 to 1.0 kV/cm is positive for growth stimulation. Conversely, those over 1.0 kV/cm resulted in growth inhibition. Furthermore, roots of the samples which exhibited increased leaf weight grew more robustly than those of decreased leaf weight. In addition, analysis results showed that there was no significant difference when liquid fertilizer was applied prior to or after application of PEF. The results suggest that PEF does not affect the composition change of liquid fertilizer but directly influences the growth of leaf lettuce.