Light In Growth Chambers Research Articles

Effects of Different Qualities of Light and Phytohormones on Seed Germination, Seedling Growth and Establishment of Papaya (Carica papaya) cv. Pusa Nanha

The present study was undertaken to study the effects of different qualities of light and phytohormones (GA3 @ 200ppm) on papaya seed germination, seedling growth, and establishment. The experiment was laid in Randomized Block Design. The experiment comprises of eight treatments viz. T0 {Natural Light (95000 lux)}, T1{Shade Net/Green House (Light 21500 lux)}, T2 {Polyhouse (light 7750 lux)}, T3 {Partially shaded area (light 2800 lux)}, T4 {Fully shaded area (light 880 lux)}, T5 {Incandescent Light (290 lux)}, T6 {Fluorescent Light (3000 lux)}, T7 {Growth Chamber Light (light 2500 lux)}. Among different treatments T6 performed best in terms of Seed germination, Seedling growth and Establishment of Papaya. The findings revealed that treatment T6 {Fluorescent Light (3000 lux)} + GA3 (200 ppm) performed best in term of Days to Germination (8 Days), Germination percentage (94.44%), Number of leaves (9.6), Plant height (16.23 cm), stem vigour index (1444.93), Leaf area (394.4 cm2), Chlorophyll content (41.47 SPAD value) and stem girth (0.37 cm), Establishment Percentage (93.33%). The highest B:C ratio was found in the same Treatment, T6 {Fluorescent Light (3000 lux)} + GA3 (200 ppm), with 3.5.

Effects of Greenhouse vs. Growth Chamber and Different Blue-Light Percentages on the Growth Performance and Quality of Broccoli Microgreens

Microgreens are a product category with a biochemical content that is currently earning them the status of a functional food. The genotype of the microgreens, and environmental factors, such as the photosynthetic photon flux density (PPFD) and light spectra, can influence the yield and biochemical profile. A landrace of broccoli called ‘Mugnoli’ was compared with a commercial variety (‘Broccolo Natalino’) in two microgreen growing systems (greenhouse vs. growth chamber) and under three growth chamber light spectra (blue, control, control + blue). The results showed that both Mugnoli and Broccolo Natalino can be used to produce microgreens, achieving similar yields, but that Mugnoli showed notably higher polyphenols and antioxidant contents. Due the higher PFFD of the greenhouse environment, microgreens yields were 18% higher than the yields from cultivation in the growth chamber. Regarding the results under different growth chamber spectra, monochromatic blue caused reductions in the microgreens yield and polyphenols content of 13.5% and 14.2%, respectively. In conclusion, Mugnoli can be considered a valuable genetic source for the production of microgreens given its fast crop cycle, good fresh weight production, and, compared to Broccolo Natalino, its superior biochemical content and lower susceptibility to PPFD variations.

Potato Tuber Growth and Yield Under Red and Blue LEDs in Plant Factories

To investigate the effects of red and blue light on potato growth and yield, potato plantlets were transplanted under white (W), red (R), blue (B), and red + blue (RB; 50%R + 50%B) light in growth chambers. Plants under W had a significantly lower tuber yield per plant than the other treatments, although their shoot dry weights were the highest among all treatments. Potato plants under R had the highest tuber yield per plant among all treatments. The distribution of tuber yield under R showed a lower ratio of 2–20 g tubers and a higher ratio of > 20 g tubers, compared to tubers under W. Plants under R had greater leaf dry weight and slowly decreasing total leaf area compared to other treatments in the late stage of potato growth, thereby extending active tuber bulking under R. Although plants under B and RB did not significantly differ in tuber yield per plant, tuber bulking under B and RB occurred in different ways. Plants under RB advanced tuberization in the seedling stage, while tubers under B rapidly accumulated biomass in the medium stage. Plants under B had higher sucrose transport from leaves to sinks and stronger tuberization signals in tubers than those under W. Tubers under B had significantly increased levels of ADP-glucose pyrophosphorylase and sucrose synthase to promote starch biosynthesis, compared to tubers under W. Overall, red light increased tuber biomass accumulation, while blue light rapidly promoted tuber bulking.

Optimal light intensity for sustainable water and energy use in indoor cultivation of lettuce and basil under red and blue LEDs

Indoor plant cultivation systems are gaining increasing popularity because of their ability to meet the needs of producing food in unfavourable climatic contexts and in urban environments, allowing high yield, high quality, and great efficiency in the use of resources such as water and nutrients. While light is one of the most important environmental factors affecting plant development and morphology, electricity costs can limit the widespread adoption of indoor plant cultivation systems at a commercial scale. LED lighting technologies for plant cultivation are also rapidly evolving, and lamps for indoor cultivation are often designed to optimize their light emissions in the photosynthetically active spectrum (i.e. red and blue), in order to reduce energetic requirements for satisfactory yield. Under these light regimens, however, little information is available in literature about minimum photosynthetic photon flux density (PPFD) for indoor production of leafy vegetables and herbs, while existing literature often adopts light intensities from 100 to 300 μmol m-2 s-1. This study aims at defining the optimal PPFD for indoor cultivation of basil (Ocimum basilicum L.) and lettuce (Lactuca sativa L.), by linking resource use efficiency to physiological responses and biomass production under different light intensities. Basil and lettuce plants were cultivated at 24 °C and 450 μmol mol-1 CO2 under red and blue light (with red:blue ratio of 3) and a photoperiod of 16 h d-1 of light in growth chambers using five PPFD (100, 150, 200, 250 and 300 μmol m-2 s-1, resulting in daily light integrals, DLI, of 5.8, 8.6, 11.5, 14.4 and 17.3 mol m-2 d-1, respectively). A progressive increase of biomass production for both lettuce and basil up to a PPFD of 250 μmol m-2 s-1 was observed, whereas no further yield increases were associated with higher PPFD (300 μmol m-2 s-1). Despite the highest stomatal conductance associated to a PPFD of 250 μmol m-2 s-1 in lettuce and to a PPFD ≥ 200 μmol m-2 s-1 in basil, water use efficiency was maximized under a PPFD ≥ 200 μmol m-2 s-1 in lettuce and PPFD ≥ 250 μmol m-2 s-1 in basil. Energy and light use efficiencies were increased under a PPFD of 200 and 250 μmol m-2 s-1 in lettuce and under a PPFD of 250 μmol m-2 s-1 in basil. Furthermore, in lettuce grown under 250 μmol m-2 s-1 antioxidant capacity, phenolics and flavonoids were higher as compared with plants supplied with PPFD ≤ 150 μmol m-2 s-1. Accordingly, a PPFD of 250 μmol m-2 s-1 seems suitable for optimizing yield and resource use efficiency in red and blue LED lighting for indoor cultivation of lettuce and basil under the prevailing conditions of the used indoor farming set-up.

Ultraviolet B radiation affects growth, physiology and fiber quality of cotton

The effects of artificial biologically effective UV-B radiation on a range of growth and physiological parameters in two cotton (Gossypium hirsutum L.) cultivars (Romanos and Allegria) were recorded. Three levels of biologically effective UV-B were used: (1) zero (2) ambient and (3) elevated (determined as that associated with a notional 15% depletion of stratospheric ozone). Plants were grown under artificial light in growth chambers and subjected to the biologically effective UV-B radiation treatments. Compared to the zero level, the ambient and elevated biologically effective UV-B radiation significantly reduced plant height, leaf chlorophyll content, net photosynthetic rate, stomatal conductance, bract length, petal length, anthers number, pollen germination, seed cotton weight, fibre strength, fibre elongation, fibre micronaire, fibre maturity index, fibre spinning consistency index, mean fibre length, fibre yellowness and fibre uniformity index. Both the ambient and the elevated UV-B radiation also significantly increased stomatal density, short fibre index and fibre reflectance. Key words: UV-B radiation, cotton, photosynthesis, stomatal density, flower characteristics, pollen germination, seed cotton weight, fibre quality.

Environmental triggers for photosynthetic protein turnover determine the optimal nitrogen distribution and partitioning in the canopy.

Plants continually adjust the photosynthetic functions in their leaves to fluctuating light, thereby optimizing the use of photosynthetic nitrogen (Nph) at the canopy level. To investigate the complex interplay between external signals during the acclimation processes, a mechanistic model based on the concept of protein turnover (synthesis and degradation) was proposed and parameterized using cucumber grown under nine combinations of nitrogen and light in growth chambers. Integrating this dynamic model into a multi-layer canopy model provided accurate predictions of photosynthetic acclimation of greenhouse cucumber canopies grown under high and low nitrogen supply in combination with day-to-day fluctuations in light at two different levels. This allowed us to quantify the degree of optimality in canopy nitrogen use for maximizing canopy carbon assimilation, which was influenced by Nph distribution along canopy depth or Nph partitioning between functional pools. Our analyses suggest that Nph distribution is close to optimum and Nph reallocation is more important under low nitrogen. Nph partitioning is only optimal under a light level similar to the average light intensity during acclimation, meaning that day-to-day light fluctuations inevitably result in suboptimal Nph partitioning. Our results provide insights into photoacclimation and can be applied to crop model improvement.

Low red: Far-red light ratio causes faster in vitro flowering in lentil

Artificial light in growth chambers typically has a higher red to far-red (R:FR) ratio compared with natural light. This higher ratio may delay flowering and reduce plant height in some long-day plants. Modification of light spectral quality to lower than the critical threshold of R:FR for a given plant species can have important implications with respect to plant structural and physiological traits. The objective of this study was to accelerate lentil (Lens culinaris) flower induction in growth chambers re-fitted with T5 fluorescent bulbs, using supplemental FR bulbs to re-balance the R:FR ratio. Lentil cultivars CDC Greenland and CDC Maxim were grown under three light sources differing in R:FR, namely light emitting diodes (LED; R:FR = 3.09), T5 fluorescent bulbs (R:FR = 5.6), and T5 supplemented with near far-red bulbs (R:FR = 3.1). All three light sources provided 500 µmol m−2 s−1 of photosynthetic photon flux (PPF). Lentil floral induction was significantly affected by the R:FR ratio. Plants grown under R:FR ratios of 3.1 or less flowered 10–11 d earlier than plants grown under an R:FR ratio of 5.6. Both cultivars had the same response to R:FR ratio in terms of days to flowering and flowering rate.

Cool-season Turfgrass Color and Growth Habit Response to Elevated Levels of Ultraviolet-B Radiation

Ultraviolet (UV) radiation poses a potential stress for plant growth and development due to its effect on photosynthesis and plant productivity. In the northern hemisphere, peak UV radiation exposure is predicted to occur from 2010 to 2020, with reduced color from UV-related injury, a possibility for turfgrasses. The objective of this study was to investigate the effects of ultraviolet-B (UV-B) light on turfgrass growth and morphology in three cool-season grasses. Cultivars Barvado tall fescue [Schedonorus arundinaceus (Schreb.) Dumort., nom. cons.], Penncross and L-93 creeping bentgrass (Agrostis stolonifera L.), and Barlenium perennial ryegrass (Lolium perenne L.), were selected because of limited information on their growth and development in elevated UV conditions at heights of cut above 10 cm. The impact of UV-B light treatment on color, relative growth rate, and tillering was measured over a 4-week period in repeated experiments. Ultraviolet-B radiation levels were measured at 16 kJ·m−2·d−1 biologically effective UV-B light in growth chambers programmed for a day/night regime of 14/10 hours. Chamber temperatures were maintained at 20 °C day/17 °C night. Ultraviolet-B light significantly inhibited tiller production in the first experiment in all grasses except PR, whereas no grasses were inhibited in the second experiment. Relative growth rates in all grasses were significantly lower in UV-B conditions 3 weeks after treatment initiation. Turfgrasses exposed to this level of UV-B light at typical lawn heights-of-cut had lower color ratings compared with the non-UV-B-treated control at 2 weeks after treatment initiation. The experiments demonstrated that exposure to UV-B resulted in a decline of growth rate and color in cool-season turfgrasses within a timeframe of 2 weeks. Coarse-textured turfgrasses [tall fescue (TF)/perennial ryegrass (PR)] may be more adapted to higher UV-B conditions due to morphological differences compared with the finer textured varieties [creeping bentgrass (CB)].

Efficient acclimation of the chloroplast antioxidant defence of Arabidopsis thaliana leaves in response to a 10- or 100-fold light increment and the possible involvement of retrograde signals

Chloroplasts are equipped with a nuclear-encoded antioxidant defence system the components of which are usually expressed at high transcript and activity levels. To significantly challenge the chloroplast antioxidant system, Arabidopsis thaliana plants, acclimated to extremely low light slightly above the light compensation point or to normal growth chamber light, were moved to high light corresponding to a 100- and 10-fold light jump, for 6 h and 24 h in order to observe the responses of the water–water cycle at the transcript, protein, enzyme activity, and metabolite levels. The plants coped efficiently with the high light regime and the photoinhibition was fully reversible. Reactive oxygen species (ROS), glutathione and ascorbate levels as well as redox states, respectively, revealed no particular oxidative stress in low-light-acclimated plants transferred to 100-fold excess light. Strong regulation of the water–water cycle enzymes at the transcript level was only partly reflected at the protein and activity levels. In general, low light plants had higher stromal (sAPX) and thylakoid ascorbate peroxidase (tAPX), dehydroascorbate reductase (DHAR), and CuZn superoxide dismutase (CuZnSOD) protein contents than normal light-grown plants. Mutants defective in components relevant for retrograde signalling, namely stn7, ex1, tpt1, and a mutant expressing E .coli catalase in the chloroplast showed unaltered transcriptional responses of water–water cycle enzymes. These findings, together with the response of marker transcripts, indicate that abscisic acid is not involved and that the plastoquinone redox state and reactive oxygen species do not play a major role in regulating the transcriptional response at t=6 h, while other marker transcripts suggest a major role for reductive power, metabolites, and lipids as signals for the response of the water–water cycle.

Cyclic electron flow around PSI monitored by afterglow luminescence in leaves of maize inbred lines (Zea mays L.): correlation with chilling tolerance

Maize (Zea mays L.) inbred lines of contrasting chilling sensitivity (three tolerant, three sensitive lines) were acclimated to 280 mumol photons m(-2) s(-1) white light at a 17 degrees C sub-optimal temperature. They showed no symptoms of photoinhibition, despite slight changes in photosystem II (PSII) fluorescence and thermoluminescence properties in two tolerant lines. A luminescence "afterglow" emission [Bertsch and Azzi (1965) Biochim Biophys Acta 94:15-26], inducible by a far-red (FR) illumination of unfrozen leaf discs, was detected either as a bounce in decay kinetics at constant temperatures or as a sharp thermoluminescence afterglow band at about 45 degrees C, in dark-adapted leaves. This band reflects the induction by warming of an electron pathway from stromal reductants to plastoquinones and to the Q(B) secondary acceptor of PSII, resulting in a luminescence-emitting charge recombination in the fraction of centres that were initially in the S(2/3)Q(B) non-luminescent state. A 5-h exposure of plants to growth chamber light shifted this luminescence emission towards shorter times and lower temperatures for several hours in the three chilling-tolerant lines. This downshift was not observed, or only transiently, in the three sensitive lines. In darkness, the downshifted afterglow band relaxed within hours to resume its dark-adapted location, similar for all maize lines. A faster dark re-reduction of P700(+) oxidized by FR light (monitored by 820-nm absorbance) and an increase of photochemical energy storage under FR excitation (determined by photoacoustic spectroscopy) confirmed that a cyclic pathway induced by white actinic light remained activated for several hours in the tolerant maize lines.

ORGANIC LIGAND-ENHANCED PHOTOCHEMICAL REDUCTION AND IMMOBILIZATION OF CHROMIUM(VI) ON TIO2 PARTICLES IN ACIDIC AQUEOUS MEDIA

Chromium(VI) is both toxic and mutagenic; Cr(III), on the other hand, is less toxic and essential for human nutrition. Thus, the reduction of Cr(VI) to less toxic Cr(III) is extremely important to decrease the potential hazard of Cr(VI) to the ecosystem. The reduction of Cr(VI) by organics alone is a slow proces; however, the simultaneous applications of light energy and activated surface sites may lead to the enhancement of Cr(VI) reduction by organic compounds. The objective of the study was to evaluate the effects of different intensities of photon flux on Cr(VI) reduction catalyzed by titanium dioxide (TiO 2 ), with or without the presence of organic compounds. The results show that less than 5% of 40 μM Cr(VI) was removed by 2 g L -1 TiO 2 in the dark. The application of fluorescence lights, however, could catalyze Cr(VI) reduction in the TiO 2 suspensions, and 40 μM Cr(VI) would be reduced upon exposure to growth chamber light at pH 2.5 within 2 days. In the absence of organics, photolysis of water molecules provided electrons for Cr(VI) reduction with the release of oxygen. Because organic compounds served as better reductants than water, light-induced TiO 2 -catalyzed Cr(VI) reduction was further enhanced. For instance, 40 μM Cr(VI) was reduced within 100 minutes in the presence of 0.2 mM HEDTA exposed to growth chamber light at pH 2.5. Therefore, to accelerate Cr(VI) reduction, lower pH (i.e., pH 2.5), stronger light intensity (i.e., growth chamber light), and decomposable organic compounds should be involved in the TiO 2 system.

Light-catalyzed chromium(VI) reduction by organic compounds and soil minerals.

Detoxification of Cr(VI) through reduction has been considered an effective method for reclaiming Cr-contaminated soil, sediment, and waste water. Organic matter is widely distributed in soil and aquatic systems; however, low Cr(VI) reduction rates inhibit the adoption of Cr reduction technologies by industry. Scientists have been aware of Cr(VI) reduction catalyzed by soil minerals; however, most of the studies focused on using semiconductors as catalysts with UV irradiation to accelerate the redox reactions. The objective of this study was to evaluate the rates of Cr(VI) reduction by fluorescence light in the presence of organic materials with or without specific soil minerals. Experimental results showed that dissolved organic compounds reduced Cr(VI) slowly under laboratory light; however, Cr(VI) reduction was greatly enhanced when growth chamber light was applied. Low photon flux (i.e., laboratory light) only enhanced Cr(VI) reduction by organics when Fe(III) was also present, because the Fe(II)-Fe(III) redox couple accelerated electron transfer and decreased electrostatic repulsion between reactants. Laboratory light was required to initiate Cr(VI) reduction catalyzed by TiO2; nonetheless, light-catalyzed Cr(VI) reduction by smectite and ferrihydrite could occur only when greater light energy was provided with a growth chamber light. Our results suggest a potential pathway for Cr(VI) reduction using naturally occurring organic compounds and colloids in acidic water systems or in surface soils when light is available.

Effects of Phosphate, HEDTA, and Light Sources on Cr(VI) Retention by Goethite

Iron hydrous hydro(oxide) has been regarded as an important sorbent for Cr(VI) in soil systems due to its wide distribution. However, many factors, such as phosphate (P), organic ligands, and light sources, could influence Cr(VI) retention by the soil components. The existence of inorganic or organic ligands not only competes with solution Cr(VI) for surface sites, but also results in releasing sorbed Cr(VI). Although organic matter can reduce Cr(VI) to less toxic Cr(III), the reduction rate is extremely slow. The objective of this study was to evaluate the influence of P on Cr(VI) sorption by goethite. The reduction of Cr(VI) by N-hydroxyethyl-ethylenediamine-triacetic acid (HEDTA) and goethite under different intensity of light was also investigated. Competitive sorption experiment indicated that P had lower inhibition of Cr(VI) sorption when the initial Cr(VI) concentration was higher than P. Goethite suspensions could catalyze Cr(VI) reduction under growth chamber light. Goethite accompanied with light could also accelerate Cr(VI) reduction by HEDTA. This phenomenon could be evidenced by the formation of Cr(III) and decreasing desorption of retained Cr(VI) by P.

Phytochrome-Mediated Detection of Changes in Reflected Light

Measurements of phytochrome photoequilibria and photoconversion rates in vivo, in seedlings of Cucurbita pepo L. exposed to light in growth chambers, indicate that significant changes in the state of phytochrome can be brought about by changes in the quality and quantity of the light reflected from the walls of the growth chambers. The changes in reflected light, although large, were small in terms of the total radiation (direct light from the lamps plus wall-reflected light) to which the seedlings were exposed. The conditions used were approximate simulations of direct and reflected sunlight conditions in the natural environment. Keeping in mind the limitations imposed by the approximation of the simulations, the results from this study are consistent with the hypothesis that, in the natural environment, a plant might be capable of detecting the presence of nearby plants, before being shaded by them, through the phytochrome-mediated perception of changes in reflected light.

Pigmentation Differences of Soybean Cultivars with Green Hypocotyl Color when Grown in Continuous Light1

Samples of 20 soybean (Glycine max L.) cultivars, classified as having green hypocotyl color, were grown in continuous 34,500 lux light. These cultivars could be placed into either of two groups based upon the presence or absence of a band of bronze pigmentation. The use of growth chamber light could be of value for the differentiation of soybean cultivars and the detection of offtypesin soybean seed lots.