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The aim of this study was to investigate the effect of red (600-700 nm, peak 660), blue (400-500 nm, peak 450) and white light on the morphological and photosynthetic qualities of Cannabis sativa L. The two treatments were the white light (WL), and a combination of blue red lights (BR). Plants grown under WL were 23% taller than those grown under the BR light emitting diodes. The leaf area was also greater under WL than BR by 20%. The number of lateral branches and length of dominant lateral branch weren´t significantly different. It was concluded WL that emit a full spectrum of light affects plant growth and development better than BR light. The quantum efficiency ranged from 0.81 to 0.845 indicating the plants were not in stress.
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November 8–9, 2017, Brno, Czech Republic 24
Department of Plant Biology
Mendel University in Brno
Zemedelska 1, 613 00 Brno
Abstract: The aim of this study was to investigate the effect of red (600–700 nm, peak 660),
blue (400–500 nm, peak 450) and white light on the morphological and photosynthetic qualities
of Cannabis sativa L. The two treatments were the white light (WL), and a combination of blue red
lights (BR). Plants grown under WL were 23% taller than those grown under the BR light emitting
diodes. The leaf area was also greater under WL than BR by 20%. The number of lateral branches and
length of dominant lateral branch weren´t significantly different. It was concluded WL that emit a full
spectrum of light affects plant growth and development better than BR light. The quantum efficiency
ranged from 0.81 to 0.845 indicating the plants were not in stress.
Key Words: Cannabis sativa L., morphology, light quality, light emitting diode.
Many species of medicinal and aromatic plants are cultivated for industrial uses
(Lubbe and Verpoorte 2011). Herbs are used in pharmaceutical and cosmetic industry for extracting
active ingredients (Roxana-Gabriela 2016). Processing of plant-derived pharmaceuticals must take
place under tightly controlled conditions, using production standards (Hefferon 2010). Since 2003
medicinal grade cannabis is provided in the Netherlands on prescription through pharmacies.
Domestic production of cannabis has been increasing in most European countries and export flows are
dynamic and changing. Denmark appears to be a center of cannabis production, and the Czech
Republic and Slovakia have become important cannabis producers and exporters to neighboring
countries (Hazekamp 2006). The European market for cannabis is extremely large, and supplying
cannabis, whether it is at the importation, production or distribution level, requires organization and
logistics, human and other resources, and the need to generate and distribute income and profits
(EMCDDA 2012). To increase the production capacity, controlled growing systems using artificial
lighting have been taken into consideration (Darko et al. 2014).
A closed system for plant production with artificial light is an innovative method of plant
cultivation (Schroeter-Zakrzewska et al. 2017). The majority of plants are grown in sealed rooms;
these being fitted with bright lights specifically designed to emit wavelengths that maximize plant
growth (EMCDDA 2012). Study conducted by Potter and Duncombe (2012), has shown that, when
light intensity is increased, the ǻ΅-tetrahydrocannabinol (THC) content of the cannabis is boosted
because plants in brighter conditions produce proportionally more female flowers, which contain
a greater concentration of THC. As an artificial light source, light-emitting diodes (LEDs) can be used
to make the plants grow more quickly in closed-type plant production systems, especially in the
environment of the light intensity is insufficient (Xu et al. 2016). LED lights do not consume much
power, do not require ballasts and produce a fraction of the heat of High intensity discharge (HID)
lamps (Thomas 2012). Their small size, durability, long operating lifetime, wavelength specificity,
relatively cool emitting surfaces, and linear photon output with electrical input current make these
solid-state light sources ideal for use in plant lighting designs (Massa et al. 2008).
Because light is such an important environmental parameter, plants have evolved numerous
biochemical and developmental responses to light that help to optimize photosynthesis and growth
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(Müller et al. 2001). Light regulates crop growth, plant development (including flowering), as well as
how quickly plants use water. Managing light is obviously critical to the production of crops grown in
controlled environments. When considering the different dimensions of light, we usually focus on
photoperiod (day length), light quantity (intensity) and light quality (the spectral distribution) (Runkle
2017). The spectral quality of lights is the relative intensity and quantity of different wavelengths
emitted by a light source and perceived by photoreceptors such as phytochromes, cryptochromes, and
phototropins, and plants generate a wide range of specific physiological responses through these
receptors. A specific light quality can be used to improve the nutritional quality of vegetables and
yields in commercial production (Kuang-Hung et al. 2012, Takemiya et al. 2005).
The objective of this study was to examine growth and development of Cannabis sativa L.
plants grown in controlled conditions under different light wavelengths. In this study, we used pure
white LEDs (Light emitting diodes) compared to red and blue LEDs (R:B = 1:1) as a light source.
Plant material
Plants of six female drug type varieties of C. Sativa (High Potency breeds acquired
from CBD Botanic, Spain) were grown in a controlled indoor growing facility at the Mendel
University in Brno, Czech Republic. The growing conditions were maintained at temperature of 25 ± 3
°C and relative humidity (RH) of 50 ± 5%. Indoor light was measured at ~200 ± 30 ȝmol mí2/s
(Quantum sensor SQ-500 series, USA) at plant canopy level for a photoperiod of 18 hours of day. Six
cuttings were made from each plant for the study. The cuttings were dipped in an auxin solution to
promote rooting and directly planted in rock wool cubes of 36x36x40 mm. The cuttings were kept in
dark for 24 hours and then transferred to the Climacell (BMT Technologies, Germany) at 24 °C and
80% RH and allowed to be rooted. After proper rooting out of the 36 cuttings, 24 healthy and
randomly selected female clones were used for the experiment.
Experimental set-up
The experiments were carried out in the Climacell Evo. The clones were divided into 12 clones
each group and placed in two different LED light treatment groups namely Red-blue (R:B) and White
light (Control). The two LED light treatments used were (1) 100% Blue and RED light and (2) 50%
White. The temperature and RH in the Climacell were maintained at 24 °C and 60% (Day) and 18 °C
and 70% (night) respectively. During the vegetative cycle 18h photoperiod was maintained for 2
weeks and during the flowering cycle 12h photoperiod was maintained for another 7 weeks. The
wavelengths of blue and red LEDs used were in the range of 420–490 nm and 630–680 nm.
Plant growth measurements
Main measured quantities in this study were plant height, number of lateral branches, leaf area,
and quantum efficiency. The leaf area was measured by the method mentioned by Pandey and Singh
(2011). Using Adobe Photoshop CS 5 and Canon EOS 1100D. For quantum yield the plants were kept
in dark to adapt for 15 mins. Next, randomly chosen leaves from six plants from each treatment were
measured using FlourPen FP 100 (Photon Systems Instruments, Czech Republic). Statistical
significance was determined by one-way ANOVA and tukeys HSD test to the treatments with
significant difference. Twelve plants were used per treatment.
Leaf Area
Plants grown under BR light had an average leaf area of 79.54 cm2 which is smaller compared
to plants grown in white light, where average leaf area was 100.03 cm2 (Figure 1).Many studies show
different light quality compared to white light have inhibiting effects on plants and their growth
as in the case with pepper, lettuce and tobacco (Brown et al. 1995, Kim 2004, Yang et al., 2016).
As Choi et al. (2016) examined effects of LED with different wavelengths on the length of petioles
and width of leaflets on strawberry plants they found out that combined illumination with red and blue
LED light was the most effective in increasing the length of petioles as well as the width of leaflets.
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In comparison with pure red LED and pure blue LED. Arena et al. (2016) found out in an experiment
with (Solanum lycopersicum L.) and (Platanus orientalis L.), growth under Red-Green-Blue (RGB)
and BR reduced leaf area compared to growth under WL. Plants that were grown under BR LED lights
had smaller leaf area by 20% than those grown under pure WL LED.
Figure 1 Average leaf area of WL and BR treatments.
Legend: WL = white light, BR = Blue-Red. Data are mean values ± SE.
Quantum Yield of Photosystem II
The photosynthetic efficiency for both the treatments appeared to be ranging
from 0.81 to 0.845. For non-stressed plants, the photosynthetic efficiency fluctuates from 0.75 to 0.85
(Bolhar–Nordenkampf et al. 1989). Which indicated that the plants were in a healthy state (Figure 2).
Figure 2 Quantum yield of photosystem II
Legends: WL = White light, BR = Blue-Red. Data are mean values ± SE.
Plant Height
There was no significant difference between the two light treated variants until the fourth week
of measurement. Since the fifth week, the plants growing in WL treatment started showing a
considerable difference in height. The difference in the heights of plants placed under BR light was
visible from the first week (Figure 3). Glowacka (2004) found tomato cultivars placed under blue light
showed shorter height compared to those kept in day light. In roses and poinsettia blue light was
known to reduce stem elongation (Islam et al. 2012, Terfa et al. 2013). In petunia blue light promotes
stem elongation on the contrary red light suppresses plant height (Fukuda et al. 2011).
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Figure 3 Plant height growth in subsequent experimental weeks.
Legends: WL = White light, BR = Blue-Red. Data are mean values ± SE.
Number of lateral branches
There were fluctuating results for lateral branches but they were not statistically significant
(data not shown). Blue light is shown to stimulate bud out growth in Triticum aestivum (Barnes and
Bugbee, 1992) and Rosa (Girault et al. 2008) whereas reduced it in Solanum tubersum (Wilson et al.
In Lilium (Vandenbussche et al. 2005) and Rosa red light inhibited lateral branching.
The plants grown under WL had and average leaf area of 100.03 cm2 compared to plants grown
in BR light with an average leaf area of 79.54 cm2. The WL treatment showed an increased plant
height compare to BR treatment. The Quantum yield of photosystem II indicated nonstressed plants.
The number of lateral branches were not affected as they did not show any significant difference.
The research was financially supported by the IGA FA MENDELU No. IP 2017/076.
We would like to express our sincere thanks to CBD Botanic (Spain) for providing us with the plant
material and support.
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... Although they do not seem to play a very important role in photosynthesis, with the activation of cryptochromes in the presence of blue and ultraviolet lights, the stem height will be affected and an increase or decrease in the number of nodes and the distance between them in plant stems can be observed (Jeong et al., 2014). Blue light, as an important light spectrum in plant growth, causes dwarfism in cannabis and reduces the distances between internodes (Lalge et al., 2017). Previous studies have also shown that the use of blue fluorescent lamps as light treatment for the ornamental plant of geranium, compared to the use of white fluorescent and incandescent lamps, reduces the stem length of this plant by less than 50%, one of the important reasons of which is the decrease in the activity of cryptochrome pigments (Appelgren, 1991). ...
... In fact, stem height is determined by how the cryptochromes function and the amount of their activity (Fukuda et al., 2016). In another study by Lalge et al. (2017), cannabis plants were examined under two light sources (red and blue spectra, white light) for 42 days. During this period, after about 30 days, a significant difference was observed between the plants in terms of stem growth and height as white light treatment resulted in higher plants in comparison with the other treatments. ...
... In addition, the expansion of leaf surface area has been proven due to the application of blue light along with the red light spectrum during the growth of lettuce (Stutte et al., 2009). Nonetheless, in relation to cannabis, by comparing the two treatments of white light and the combination of red and blue lights, the widest leaf surface area was observed under the white light treatment, and the blue and red light spectra had no significant effect on leaf surface area (leaf length and width) (Lalge et al., 2017). It is to be noted that a similar effect has been reported in radish leaves (Samuolienė et al., 2011). ...
Cannabis which is a medicinal and industrial plant is native to Central Asia. It has been used as a source of food, fuel, fiber, medicine, and drugs for centuries. Cannabis has valuable agronomic traits, such as being easy to cultivate and creating diversity in organic farming. From an agricultural point of view, it is a high-yielding crop and does not require much pesticide, herbicide, and fertilizer compared to other kinds of crops, and therefore will have a less negative impact on the environment. Cannabis seeds are rich in protein and oil and have long been used by humans. Cannabis sativa seed oil contains good amounts of unsaturated fatty acids, including linoleic acid and linolenic acid, which are good for human nutrition and health and reduce cholesterol and high blood pressure. Cannabis can also be considered an excellent option for the production of two important biofuels, namely, biodiesel and bioethanol. In terms of phytochemicals, this plant is very complex and it contains more than 480 different chemical compounds. Some of these compounds belong to the primary metabolites such as amino acids, fatty acids, and steroids, while compounds such as cannabinoids, flavonoids, acetylbenoids, terpenoids, lignans (phenolic amides and lignamides), and alkaloids are among the secondary metabolites produced by the valuable cannabis plant. Therefore cannabis is similar to a very strong factory in terms of phytochemicals, which has a high value in the pharmaceutical industry. Today, the positive effect of cannabis pharmaceutical compounds has been reported in studies done on the effect of cannabis on various diseases, such as cancer, multipple sclerosis (MS), and acquired immune deficiency syndrome (AIDS), which further increases the value of this plant. As a result, due to the high importance of cannabis in pharmacy, medicine, and industry, agricultural science must study the environmental factors affecting the cultivation of this valuable plant to increase its yield and efficiency of the plant. Today, light-emitting diodes are considered an influential factor in the production of agricultural products by many researchers. Over the past years, several studies have been conducted on the effect of light spectra on plant growth and development, which have well demonstrated the importance of the blue and red spectra. Consequently, finding the right combination of light spectra for better growth and development of plants, including cannabis, is under investigation to get the best performance from the plant at the most appropriate time.
... The most common light source used nowadays for indoor cannabis production is light emitting diodes (LEDs) which can have a widely varying spectrum [23,25]. Recent findings suggest that blue light increased fresh and dry biomass in industrial hemp, plant height, and number of leaves per plant [25] while the combination of red and blue light resulted in smaller leaf area and more compact morphology in comparison to a white light source [26,27]. ...
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Industrial hemp is a fast-growing, short-day plant, characterized by high biomass yields and low demands for cultivation. To manipulate growth, hemp is usually cultivated under prolonged photoperiods or continuous light that could cause photooxidative damage and adjustments of photosynthetic reactions. To determine the extent of changes in photosynthetic response caused by prolonged light exposure, we employed chlorophyll a fluorescence measurements accompanied with level of lipid peroxidation (TBARS) and FT-IR spectroscopy on two Cannabis cultivars. Plants were grown under white (W) and purple (P) light at different photoperiods (16/8, 20/4, and 24/0). Our results showed diverse photosynthetic reactions induced by the different light type and by the duration of light exposure in two cultivars. The most beneficial condition was the 16/8 photoperiod, regardless of the light type since it brought the most efficient physiological response and the lowest TBARS contents suggesting the lowest level of thylakoid membrane damage. These findings indicate that different efficient adaptation strategies were employed based on the type of light and the duration of photoperiod. White light, at both photoperiods, caused higher dissipation of excess light causing reduced pressure on PSI. Efficient dissipation of excess energy and formation of cyclic electron transport around PSI suggests that P20/4 initiated an efficient repair system. The P24/0 maintained functional electron transport between two photosystems suggesting a positive effect on the photosynthetic reaction despite the damage to thylakoid membranes.
... In some cases, blue light was noted to produce an enhanced biochemical yield in plants by increasing the plant's chlorophyll pigments. Also, red LED had produced shoots on the explant in some plants, Despite these facts, monochromatic blue and red lights did not produce enhanced responses among the many other growing plantlets 1,7,30 . ...
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The use of artificial light sources such as light-emitting diodes (LEDs) has become a prerequisite in tissue culture studies to obtain morphogenetic enhancements on in vitro plants. This technology is essential for developmental enhancements in the growing plant cultures due to its light quality and intensity greatly influencing the in vitro growing explants at a cellular level. The current study investigates the effects of different light-emitting diode (LED) spectra on the growth of apical buds of Ficus carica var. Black Jack. Ficus carica, commonly known as figs is rich in vitamins, minerals, and phytochemicals capable of treating microbial infections and gastric, inflammatory, and cardiac disorders. Apical buds of Ficus carica var. Black Jack, presented morphogenetic changes when grown under six different LED spectra. The highest multiple shoots (1.80 per growing explant) and healthy growing cultures were observed under the blue + red LED spectrum. Wound-induced callus formation was observed on apical buds grown under green LED spectrum and discolouration of the growing shoots were observed on the cultures grown under far-red LED spectrum. Multiple shoots obtained from the blue + red LED treatment were rooted using 8 µM indole-3-acetic acid (IAA), and the rooted plantlets were successfully acclimatised. Compared with the other monochromatic LEDs, blue + red proved to be significantly better for producing excellent plant morphogeny. It is apparent that blue and red LED is the most suitable spectra for the healthy development of plants. The findings have confirmed that the combination of blue + red LED can potentially be used for enhancing growth yields of medicinally and commercially important plants.
... Dynamic interactions between light and exogenous sugar are important for evoking many additional physiological responses relating to light attenuation and metabolism (Tichá et al., 1998;Roh and Choi, 2004;Gago et al., 2014). Lalge et al. (2017) observed that taller cannabis clones developed with W compared to B + R LEDs when grown in controlled climates. The optimal levels of R:Fr in promoting stem elongation has been well-documented (Trupkin et al., 2014;Ballaré and Pierik, 2017;Ma and Li, 2019). ...
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Micropropagation techniques offer opportunity to proliferate, maintain, and study dynamic plant responses in highly controlled environments without confounding external influences, forming the basis for many biotechnological applications. With medicinal and recreational interests for Cannabis sativa L. growing, research related to the optimization of in vitro practices is needed to improve current methods while boosting our understanding of the underlying physiological processes. Unfortunately, due to the exorbitantly large array of factors influencing tissue culture, existing approaches to optimize in vitro methods are tedious and time-consuming. Therefore, there is great potential to use new computational methodologies for analyzing data to develop improved protocols more efficiently. Here, we first tested the effects of light qualities using assorted combinations of Red, Blue, Far Red, and White spanning 0–100 μmol/m2/s in combination with sucrose concentrations ranging from 1 to 6% (w/v), totaling 66 treatments, on in vitro shoot growth, root development, number of nodes, shoot emergence, and canopy surface area. Collected data were then assessed using multilayer perceptron (MLP), generalized regression neural network (GRNN), and adaptive neuro-fuzzy inference system (ANFIS) to model and predict in vitro Cannabis growth and development. Based on the results, GRNN had better performance than MLP or ANFIS and was consequently selected to link different optimization algorithms [genetic algorithm (GA), biogeography-based optimization (BBO), interior search algorithm (ISA), and symbiotic organisms search (SOS)] for prediction of optimal light levels (quality/intensity) and sucrose concentration for various applications. Predictions of in vitro conditions to refine growth responses were subsequently tested in a validation experiment and data showed no significant differences between predicted optimized values and observed data. Thus, this study demonstrates the potential of machine learning and optimization algorithms to predict the most favorable light combinations and sucrose levels to elicit specific developmental responses. Based on these, recommendations of light and carbohydrate levels to promote specific developmental outcomes for in vitro Cannabis are suggested. Ultimately, this work showcases the importance of light quality and carbohydrate supply in directing plant development as well as the power of machine learning approaches to investigate complex interactions in plant tissue culture.
... Besides yield, light in particular influences plant morphology, mixing red and blue light caused shorter internodes, smaller leaf area and more compact morphology compared to a pure white light source [30]. A significant increase in yield and concentration of total Δ 9 -tetrahydrocannabinol (THC) was reported when using intracanopy red and blue lighting compared to the sunlight control treatment [31]. ...
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Cannabis is one of the oldest cultivated plants, but plant breeding and cultivation are restricted by country specific regulations. Plant growth, morphology and metabolism can be manipulated by changing light quality and intensity. Three morphologically different strains were grown under three different light spectra with three real light repetitions. Light dispersion was included into the statistical evaluation. The light spectra considered had an influence on the morphology of the plant, especially the height. Here, the shade avoidance induced by the lower R:FR ratio under the ceramic metal halide lamp (CHD) was of particular interest. The sugar leaves seemed to be of elementary importance in the last growth phase for yield composition. Furthermore, the last four weeks of flowering were crucial to influence the yield composition of Cannabis sativa L. through light spectra. The dry flower yield was significantly higher under both LED treatments compared to the conventional CHD light source. Our results indicate that the plant morphology can be artificially manipulated by the choice of light treatment to create shorter plants with more lateral branches which seem to be beneficial for yield development. Furthermore, the choice of cultivar has to be taken into account when interpreting results of light studies, as Cannabis sativa L. subspecies and thus bred strains highly differ in their phenotypic characteristics.
Cannabis sativa L. has raised a lot of interest in recent years, due to the different utilities of the plant, being useful in different types of industries, as well as the discovery of possible therapeutic utilities of different secondary metabolites of the plant. This chapter presents the effect of the different environmental factors on the different vital phases of the plant, emphasizing its effects on its secondary metabolism. Secondly, we will review different agronomic techniques related to irrigation, the behavior of the plant in water scarcity scenarios, mineral nutrition and the use of different phytohormones and chemical supplements, focusing on their influence on the secondary metabolism of C. sativa L. Finally, the use of the novel biostimulants and biocontrols in this crop and their future prospects are discussed.
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A closed system for plant production with artificial light is an innovative method of plant cultivation. By placing plants on shelves, higher space efficiency is achieved and costs of heating are reduced as compared to greenhouse cultivation. The aim of the study was to assess the influence of light colour and type of lamps on the quality and nutrient status of chrysanthemums (Chrysanthemum x grandiflorum Ramat./Kitam.) cultivated in a growth chamber with no access to natural light. Two-factorial experiments were conducted: (factor A: lamp type: LED and fluorescent, factor B: light colour: Red (denoted as R), Blue+White (B+W), Red+Blue (R+B); Green (G); White (W), Blue (B). For all colours the quantum irradiance was 35 µmol m⁻² s⁻¹ and the day length was 10 hours. The plant growing experiments were conducted in a controlled environment growth room. Measurements and observations were carried out at anthesis when 50% of all flower heads were completely developed. The measurements referred to plant features determining plant quality, i.e. the number of flower buds and flower head, diameter of flower head, height and diameter of plants, index of leaf greenness (SPAD). Plant quality was significantly dependent on light colour and the type of lamps used. Earlier flowering of plants was observed under LED lamps emitting white and blue light. The largest flower heads were produced by plants grown under blue and red + blue colour light. Red light emitted by both types of lamps had an adverse effect on plant flowering. Both the type of lamps and the colour of emitted light significantly modified the plant nutrient status. Interactions between the studied factors were found. The mean content of nitrogen, phosphorus, calcium, magnesium and sulphur was higher in plants grown under LED than FL lamps. A similar trend was also found for the microelement content. © 2017, Polish Society Magnesium Research. All rights reserved.
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In the present study, we investigated changes in chlorophyll fluorescence, photosynthetic parameters and fruit yields, as well as fruit phytochemical accumulation of strawberry (Fragaria ananassa Duch.) that had been cultivated in a greenhouse under different combinations of light intensity and temperature. In plants grown with low light (LL) photosystem II chlorophyll fluorescence was found to increase as compared with those grown under high light (HL). When strawberry plants were grown with temperature higher than 5°C in addition to LL, they showed decrease in non-photochemical quenching (NPQ), photochemical quenching (qP), as well as chlorophyll fluorescence decrease ratio (RFd) when compared with other combinations of light and temperature. Moreover, fruit yield of strawberry was closely correlated with chlorophyll fluorescence-related parameters such as NPQ, qP, and RFd, but not with the maximum efficiency of PS II (Fv/Fm). Although plant groups grown under different combinations of light and temperature showed almost comparable levels of photosynthesis rates (Pr) when irradiated with low-intensity light, they displayed clear differences when measured with higher irradiances. Plants grown under HL with temperature above 10°C showed the highest Pr, in contrast to the plants grown under LL with temperature above 5°C. When the stomatal conductance and the transpiration rate were measured, plants of each treatment showed clear differences even when analyzed with lower irradiances. We also found that fruit production during winter season was more strongly influenced by growth temperature than light intensity. We suggest that fruit productivity of strawberry is closely associated with chlorophyll fluorescence and photosynthesis-related parameters during cultivation under different regimes of temperature and light.
In this study, effects of yellow (Y), purple (P), red (R), blue (B), green (G), and white (W) light on growth and development of tobacco plants were evaluated. We showed that monochromatic light reduced the growth, net photosynthetic rate (PN), stomatal conductance, intercellular CO2, and transpiration rate of tobacco. Such a reduction in PN occurred probably due to the stomatal limitation contrary to plants grown under W. Photochemical quenching coefficient (qP), maximal fluorescence of dark-adapted state, effective quantum yield of PSII photochemistry (ΦPSII), and maximal quantum yield of PSII photochemistry (Fv/Fm) of plants decreased under all monochromatic illuminations. The decline in ΦPSII occurred mostly due to the reduction in qP. The increase in minimal fluorescence of dark-adapted state and the decrease in Fv/Fm indicated the damage or inactivation of the reaction center of PSII under monochromatic light. Plants under Y and G showed the maximal nonphotochemical quenching with minimum PN compared with the W plants. Morphogenesis of plants was also affected by light quality. Under B light, plants exhibited smaller angles between stem and petiole, and the whole plants showed a compact type, while the angles increased under Y, P, R, and G and the plants were of an unconsolidated style. The total soluble sugar content increased significantly under B. The reducing sugar content increased under B but decreased significantly under R and G compared with W. In conclusion, different monochromatic light quality inhibited plants growth by reducing the activity of photosynthetic apparatus in plants. R and B light were more effective to drive photosynthesis and promote the plant growth, while Y and G light showed an suppression effect on plants growth. LEDs could be used as optimal light resources for plant cultivation in a greenhouse.
The effect of different light qualities on growth, photosynthesis, leaf anatomy and isoprenoid emission was studied in two different fast-growing plant systems: a herbaceous crop, tomato (Solanum lycopersicum L.), and a tree, oriental plane (Platanus orientalis L.). Both plant species were subjected to three different light quality regimes: RGB (Red 33%, Green 33%, Blue 33%) and RB (Red 66%, Blue 33%), provided by light emitting diodes (LED); and white light (WL), considered as a control and provided by white fluorescent lamps. Compared to WL, RGB and RB reduced plant height, plant biomass and leaf area. The CO2 assimilation rate (A) was lower in tomato grown under WL than RGB and RB, while A was similar in oriental plane leaves exposed to the three light regimes. In tomato, stomatal (gs) and mesophyll (gm) conductance were higher under RGB and RB compared to WL. In plane, gs was also higher under RGB and RB, while gm was not significantly influenced by different light qualities. In both species, leaf lamina thickness (LT) and stomata size were the anatomical traits most affected by the different light regimes. In tomato, leaf lamina thickness was significantly reduced in RGB and RB leaves, whereas in oriental plane leaf lamina thickness was significantly higher in RGB and RB than in WL leaves. In both species, RB leaves showed bigger stomata size than WL and RGB leaves. Light quality also affected photosynthesis-dependent volatile isoprenoids. In tomato, β-phellandrene was lower under RB and RGB compared to WL. However, RGB and RB stimulated α-pinene, carene and α-terpinene emissions. Oriental plane released about 14 nmol m−2 s−1 isoprene when growing at WL, while the emission was reduced under RGB and even more under RB. In summary, photosynthetic performance, leaf anatomy, biomass production, and volatile isoprenoids are affected by light quality differently in tomato and plane plants. Light quality control may have important applications to modulate plant productivity and increase biosynthesis of useful biochemical compounds.
As an artificial light source, light-emitting diodes (LEDs) can be used to make the vegetables grow more quickly in closed-type plant production systems, especially in the environment of the light intensity is insufficient. In order to study the improvement of the cherry tomato growth rate using the LED light source, we have a design with a certain ratio of red and blue (relative spectral distribution) LED lighting system and carry out the manufacture of the LED supplementary lighting system. We carried on a track on the growth situation for a group of cherry tomatoes under the LED system and the other group of cherry tomatoes without the LED supplementary lighting system. We observed and compared with the growth of the two group of tomatoes in different growing period. In our experiment, we use supplementary lighting system with the red and blue LEDs which peak wavelenth are respectively 650 nm and 460nm, and the relative spectral distribution ratio is 4:1. The experimental results showed that the LED supplementary lighting system significantly improved the growth speed of tomatoes. Because of the difference preference for the wavelength between the stem and leaf growth stage and the blooming and bearing fruit growth stage, this paper presents the red and blue light proportion choice switch which can be applied to the LED supplementary lighting system.
Light-emitting diodes (LEDs) have tremendous potential as supplemental or sole-source lighting systems for crop production both on and off earth. Their small size, durability, long operating lifetime, wavelength specificity, relatively cool emitting surfaces, and linear photon output with electrical input current make these solid-state light sources ideal for use in plant lighting designs. Because the output waveband of LEDs (single color, nonphosphor-coated) is much narrower than that of traditional sources of electric lighting used for plant growth, one challenge in designing an optimum plant lighting system is to determine wavelengths essential for specific crops. Work at NASA's Kennedy Space Center has focused on the proportion of blue light required for normal plant growth as well as the optimum wavelength of red and the red/far-red ratio. The addition of green wavelengths for improved plant growth as well as for visual monitoring of plant status has been addressed. Like with other light sources, spectral quality of LEDs can have dramatic effects on crop anatomy and morphology as well as nutrient uptake and pathogen development. Work at Purdue University has focused on geometry of light delivery to improve energy use efficiency of a crop lighting system. Additionally, foliar intumescence developing in the absence of ultraviolet light or other less understood stimuli could become a serious limitation for some crops lighted solely by narrow-band LEDs. Ways to prevent this condition are being investigated. Potential LED benefits to the controlled environment agriculture industry are numerous and more work needs to be done to position horticulture at the forefront of this promising technology.
Chlorophyll fluorescence has been widely used in laboratory studies in understanding both the mechanism of photosynthesis itself and the mechanisms by which a range of environmental factors alter photosynthetic capacity. The measurement of chlorophyll fluorescence is both non-destructive and non-invasive, and thus has considerable potential for use in the field situation. Applications range simply from a means of rapidly identifying injury to leaves in the absence of visible symptoms to a detailed analysis of causes of change in photosynthetic capacity. This paper introduces the topic of chlorophyll fluorescence, its interpretation and its application in field studies, giving particular attention to interpretation and measurement of fluorescence induction kinetics and to the application of recently developed modulated light fluorimeters. Three commercial fluorimeters designed for field applications were compared: (1) Plant Stress Meter, BioMonitor AB, Sweden; (2) MFMS, Hansatech Ltd, UK; (3) PAM 101, H. Walz, Federal Republic of Germany. The structure and potential of each are briefly reviewed. It was beyond the scope of this comparison to examine the full potential of each instrument but measurements of the widely used parameter F<sub>v</sub>/F<sub>max</sub> were made with each on: (1) Triticum aestivum L. leaves treated with the herbicide Atrazine; and (2) Picea abies (L.) Karst. samples collected from sites which were known to receive different levels of ambient air pollution. In both experiments, the results obtained from the three fluorimeters showed good agreement. The relative merits of each instrument to field applications are discussed.
Transplants of the tomato cultivars 'Recento F 1 ', 'Tukan F 1 ', and 'Remiz F 1 ' were grown under fluorescent lamps emitting daylight and blue light with quantum irradiance 67 µmol m -2 s -1 . The morphological attributes, as plant height, stem thickness, number of leaves, length of internodes, fresh and dry mass were investigated. Irrespective of the cultivar, favourable influence of the blue light was observed. Those plants were short, with thick and strong stem, shortened internodes, enhanced participation of the dry mass in fresh mass. The first clusters were set considerably lower. The application of the lamps emitting blue light can be an effective and environment-friendly method of controlling the growth of tomato transplant.