Light Deprivation Research Articles

Several short-day species can flower under blue-extended long days, but this response is not universal

Sole-source LED lighting enables spectral flexibility to achieve desirable plant characteristics and product quality. An earlier study from our lab showed that short-day plant chrysanthemum flowers normally under long days with dynamic lighting of 11 h dichromatic red-blue LED light extended with 4 h sole blue LED light. Such dynamic LED lighting is possible in vertical farms and opens the possibility to supply a higher daily light integral (DLI) to short-day plants by providing more hours of light and thus increase growth rate. This study aims to investigate for several short-day species whether normal flowering is obtained when 11 h of red-blue is extended with 4 h of sole blue LED light. Twelve genotypes of nine short-day plants species (kalanchoe - Kalanchoe blossfeldiana, perilla - Perilla frutescens, stevia - Stevia rebaudiana, artemisia - Artemisia annua, chrysanthemum - Chrysanthemum seticuspe and Chrysanthemum morifolium, cosmos - Cosmos bipinnatus, poinsettia - Poinsettia pulcherrima and wild tomato - Solanum habrochaites) were grown at three light conditions in a climate room: 11 h red-blue short day, 11 h red-blue extended with 4 h of sole blue, and 15 h red-blue long day. Mixed red and blue light (ratio 60:40) was provided at a total photosynthetic photon flux density (PPFD) of 100 µmol m−2 s−1 and sole blue light was provided at 40 µmol m−2 s−1 PPFD. Flowering response differed among species: kalanchoe, perilla and stevia flowered only in red-blue short day. Artemisia, chrysanthemum, cosmos, poinsettia, and wild tomato flowered in red-blue short day, and blue-extended long day but not in red-blue long day. However, there was a flowering delay in cosmos, poinsettia, and wild tomato under blue-extended long days compared to short days. In blue-extended long days plants received 15 % higher DLI resulting in a 4 to 36 % increase in total dry weight compared to short days. This study shows that increasing growth rate under light-limiting growth conditions through daylength-extension with sole blue light, without compromising flowering and quality, is possible for some, but not all short-day species.

Corydalis speciosa Maxim. is a day-neutral plant with an obligate cold requirement

In the modern floricultural industry, there is a market demand for a continuous supply of products, imposing the need for year-round production. The most common and efficient tools for the manipulation of flowering are photoperiodic control and cold treatment. The objective of this study was to identify the cold and daylength requirements for flowering of Korean native biennial Corydalis speciosa Maxim.. The Year 1 experiment was designed to observe the general response of the plant in a greenhouse. Nine-week-old seedlings were treated with 5°C cold for 0, 4, or 8 weeks and then grown under a 9/15-, 12/12-, 14/10-, 16/8-, or 24/0-h photoperiod. The Year 2 experiment aimed to determine the plant response in a more controlled environment using a growth chamber. Seedlings were divided into two stages to examine the age-dependent response. Five-week-old (Stage 1, 5 leaves) or 8-week-old (Stage 2, 10 leaves) seedlings were treated with 5°C cold for 0, 4, 8, or 12 weeks. Plants were grown under a 12/12-h photoperiod because the Year 1 experiment did not show any photoperiodic response. The results from Year 1 demonstrated no photoperiodic response with an obligate cold requirement for flowering. The average flowering percentages were 36% under 4 weeks of cold and 100% under 8 weeks of cold. The Year 2 experiment revealed no significant effect of seedling age on flowering. The average flowering percentages in Year 2 were 81% under 8 weeks of cold and 100% under 12 weeks of cold. The higher flowering rate in Year 1 was presumably because the greenhouse temperature fell below 5°C during the experiment and extended cold exposure. Based on these results, it can be concluded that C. speciosa is a day-neutral plant with an obligate cold requirement of at least 8 weeks.

Circadian clock does not play an essential role in daylength measurement for growth-phase transition in Marchantia polymorpha.

Daylength is perceived as a seasonal cue to induce growth-phase transition at a proper time of a year. The core of the mechanism of daylength measurement in angiosperms lies in the circadian clock-controlled expression of regulators of growth-phase transition. However, the roles of the circadian clock in daylength measurement in basal land plants remain largely unknown. In this study, we investigated the contribution of circadian clock to daylength measurement in a basal land plant, the liverwort Marchantia polymorpha. In M. polymorpha, transition from vegetative to reproductive phase under long-day conditions results in differentiation of sexual branches called gametangiophores which harbor gametangia. First, we showed that a widely used wild-type accession Takaragaike-1 is an obligate long-day plant with a critical daylength of about 10 hours and requires multiple long days. Then, we compared the timing of gametangiophore formation between wild type and circadian clock mutants in long-day and short-day conditions. Mutations in two clock genes, MpTIMING OF CAB EXPRESSION 1 and MpPSEUDO-RESPONSE REGULATOR, had no significant effects on the timing of gametangiophore formation. In addition, when M. polymorpha plants were treated with a chemical which lengthens circadian period, there was no significant effect on the timing of gametangiophore formation, either. We next observed the timing of gametangiophore formation under various non-24-h light/dark cycles to examine the effect of phase alteration in circadian rhythms. The results suggest that daylength measurement in M. polymorpha is based on the relative amount of light and darkness within a cycle rather than the intrinsic rhythms generated by circadian clock. Our findings suggest that M. polymorpha has a daylength measurement system which is different from that of angiosperms centered on the circadian clock function.

Genome-wide association study and transcriptome analysis reveal candidate genes for off-season flowering in blueberry

Off-season flowering in daylength-sensitive plants is an intriguing characteristic that represents an opportunity to expand crop's production timing and regions, and potentially speed up breeding. Southern Highbush Blueberry (SHB) is classified as a short-day plant, with a blooming period in the northern hemisphere ranging from late winter through spring. In Florida, some blueberry genotypes have consistently bloomed during the fall season, suggesting that flower bud initiation occurred during the summer. Such a characteristic indicates a facultative response to daylength or day-neutrality capacity, leading to the off-season flowering observed. To understand the genetic basis of off-season flowering in SHB, we performed a genome-wide association study (GWAS), followed by transcriptomic analysis of contrasting genotypes. Among the 536 genotypes evaluated, 14 % bloomed during the fall, of which seven presented consistently high scores for off-season flowering capacity. The GWAS revealed 12 single nucleotide polymorphisms (SNPs) significantly associated with the off-season flowering trait, which together accounted for 17 % of the phenotypic variance. A gene homologous to an RNA helicase and reported to modulate florescence formation and flowering time in other plant species, was identified within a genomic region associated with the off-season flowering. This gene was up-regulated in a fall-flowering blueberry genotype. Additionally, we detected down-regulation of flowering repressors and up-regulation of MADS-box transcription factors known to be involved in the fate of floral meristems. Our findings provide insights into the genetic and molecular basis of this complex trait in blueberry. These results can be useful for marker-assisted selection and further functional gene validation to accelerate the development of blueberry varieties suitable for off-season production.

Transcriptomic response for revealing the molecular mechanism of oat flowering under different photoperiods.

Proper flowering is essential for the reproduction of all kinds of plants. Oat is an important cereal and forage crop; however, its cultivation is limited because it is a long-day plant. The molecular mechanism by which oats respond to different photoperiods is still unclear. In this study, oat plants were treated under long-day and short-day photoperiods for 10 days, 15 days, 20 days, 25 days, 30 days, 40 days and 50 days, respectively. Under the long-day treatment, oats entered the reproductive stage, while oats remained vegetative under the short-day treatment. Forty-two samples were subjected to RNA-Seq to compare the gene expression patterns of oat under long- and short-day photoperiods. A total of 634-5,974 differentially expressed genes (DEGs) were identified for each time point, while the floral organ primordium differentiation stage showed the largest number of DEGs, and the spikelet differentiation stage showed the smallest number. Gene Ontology (GO) analysis showed that the plant hormone signaling transduction and hormone metabolism processes significantly changed in the photoperiod regulation of flowering time in oat. Moreover, Kyoto Encyclopedia of Genes and Genomes (KEGG) and Mapman analysis revealed that the DEGs were mainly concentrated in the circadian rhythm, protein antenna pathways and sucrose metabolism process. Additionally, transcription factors (TFs) involved in various flowering pathways were explored. Combining all this information, we established a molecular model of oat flowering induced by a long-day photoperiod. Taken together, the long-day photoperiod has a large effect at both the morphological and transcriptomic levels, and these responses ultimately promote flowering in oat. Our findings expand the understanding of oat as a long-day plant, and the explored genes could be used in molecular breeding to help break its cultivation limitations in the future.

Influence of the spectral composition of light on the morphogenesis of seedlings of <i>Myrtus communis</i> L. and <i>Psidium cattleianum</i> Sabine (<i>Myrtaceae</i> Juss.) in a small pot greenhouse culture

The influence of the intensity and spectral composition of LED and fluorescent (FL) light on the morphogenesis of Myrtus communis L. and Psidium cattleianum Sabine (Myrtaceae) seedlings in a small pot greenhouse culture in the Central Botanical Garden of the National Academy of Sciences of Belarus (CBG) was studied. It was shown that in terms of plant height, the number and total surface of leaves, as well as the specific dry weight of the leaf, seedlings of both species over 120 cultivation days in all variants with irradiation surpassed control plants. The increase in dry weight per 1 cm2 of leaf (mg with respect to the control) that characterizes the photosynthesis productivity was influenced by the spectral composition of radiation, which made it possible to identify interspecies and intervariant differences. The variant with an FL Narva lamp with a total photon flux density PFD = 76.22 µmol/m2/s, with a share of the green spectrum PFD-G = 46.47 %, red – PFD-R = 20.00 % and with the value of the ratio R/FR = 5.77 in the subtropical long-day species M. communis, it was 1.24 mg, while in the tropical short-day species P. cattleianum had only 0.39 mg. In plants irradiated with an LED lamp with a photon flux density PFD = 186.20 µmol/m2/s, with a share of PFD-R = 59.34 %, and at R/FR = 54.43, the growth was 2.60 and 1.93 mg with respect to control, respectively. LED sources are the most efficient in terms of the photosynthesis productivity for both short-day and long day plants.

Effects of end-of-day far-red light and relative humidity on flowering and stem elongation of petunia (Petunia × hybrida) seedlings

Far-red light at the end of the day (EOD-FR) can promote the flowering of long-day plants. However, it can cause excessive stem elongation that reduces the quality of transplants. Therefore, flowering and stem elongation must be balanced when EOD-FR is used in bedding-plant production. Here, we examined the interactive role of relative humidity (RH) to suppress excessive elongation caused by EOD-FR and the combined effects of EOD-FR and RH on flowering and stem elongation of petunia (Petunia × hybrida) seedlings. We grew seedlings for 28 days in controlled-environment chambers after two true leaves had expanded, with or without EOD-FR, at 40 % or 80 % RH. We found a significant EOD-FR × RH interaction in stem length, with a smaller increase in stem length due to EOD-FR at lower RH. Flower development, which was evaluated using the node position at first flowering, was promoted by EOD-FR. However, low RH suppressed flower development both with and without EOD-FR, thereby counteracting the promotion of flower development by EOD-FR. Thus, EOD-FR treatment at low RH could not prevent excessive stem elongation while promoting flowering. Clarifying the eco-physiological reasons why low RH counteracts the FR-induced promotion of flowering associated with the shade-avoidance response may be necessary to improve flowering control with bedding plant transplants under a controlled environment.

Daylength variation affects growth, photosynthesis, leaf metabolism, partitioning, and metabolic fluxes.

Daylength, a seasonal and latitudinal variable, exerts a substantial impact on plant growth. However, the relationship between daylength and growth is nonproportional, suggesting the existence of adaptive mechanisms. Thus, our study aimed to comprehensively investigate the adaptive strategies employed by plants in response to daylength variation. We grew false flax (Camelina sativa) plants, a model oilseed crop, under long-day (LD) and short-day (SD) conditions and used growth measurements, gas exchange measurements, and isotopic labeling techniques, including 13C, 14C, and 2H2O, to determine responses to different daylengths. Our findings revealed that daylength influences various growth parameters, photosynthetic physiology, carbon partitioning, metabolic fluxes, and metabolite levels. SD plants employed diverse mechanisms to compensate for reduced CO2 fixation in the shorter photoperiod. These mechanisms included enhanced photosynthetic rates and reduced respiration in the light (RL), leading to increased shoot investment. Additionally, SD plants exhibited reduced rates of the glucose 6-phosphate (G6P) shunt and greater partitioning of sugars into starch, thereby sustaining carbon availability during the longer night. Isotopic labeling results further demonstrated substantial alterations in the partitioning of amino acids and TCA cycle intermediates between rapidly and slowly turning over pools. Overall, the results point to multiple developmental, physiological, and metabolic ways in which plants adapt to different daylengths to maintain growth.

Photoperiod sensitivity of Ppd-H1 and ppd-H1 isogenic lines of a spring barley cultivar: exploring extreme photoperiods.

Barley is a long-day plant with a major gene (PPD-H1) that determines its photoperiod sensitivity. Under long days (i.e. 16 h), flowering occurs earlier in sensitive (Ppd-H1) than in insensitive (ppd-H1) genotypes, while under short days (i.e. 12 h) both flower late and more or less simultaneously. We hypothesized that (i) the sensitive line should flower later than the insensitive line under very short days (<12 h), and (ii) both the sensitive and insensitive lines should have similar phenology under very long days (>18 h). When comparing a pair of spring isogenic lines for sensitive and insensitive PPD-H1 alleles (introgressing the PPD-H1 allele into the barley cultivar 'WI4441'), we found responses fully in line with expectations for the commonly explored range from 12 to 16-18 h. When the responses were extended to very short days, sensitivity increased noticeably, and time to flowering of the sensitive line was longer than that of the insensitive one. Under very long days, the sensitive line did not respond further (it seemed to have reached its minimum time to flowering under a 16 h period), while the insensitive line continued shortening its time to flowering until c. 21 h. Consequently, both lines flowered similarly under very long days, which opens opportunities to easily test for differences in earliness per se, as in wheat.

Invited Session II: Myopia and myopia control: Interactions between Light Exposure and Diurnal Rhythms on the Choroid.

Increasing evidence demonstrates that light exposure and circadian rhythms plays a role in myopia, with high intensity outdoor light being protective. The choroid may be involved in this mechanism. The goals of our studies were to examine the interaction between light exposure and circadian influences on the choroid. In Experiment 1, choroid diurnal rhythms were investigated during monocular light deprivation in adults using spectral domain optical coherence tomography imaging (SD-OCT). The left eye was light deprived for 20 hours. In Experiment 2, the effects of two hours of high intensity outdoor light exposure on retinal and choroid thickness were investigated and compared to indoor illumination and darkness. For Experiment 1, choroid diurnal variation persisted and retinal diurnal variation was eliminated in light deprived eyes. Total retinal and inner segment thicknesses decreased (P < 0.001) and outer segment + RPE thickness increased (P < 0.05) with light deprivation. For Experiment 2, the choroid was significantly thinner during outdoor light exposure compared to indoors and darkness (P < .01), but returned to baseline at follow-up (P > .05). Total retinal thickness was significantly thicker during and after the outdoor compared to indoor and dark conditions (P < .05). These studies demonstrate that the choroid is mediated by both intrinsic circadian mechanisms as well as light exposure. Choroidal thickness rhythms were not impacted by short-term light deprivation. Surprisingly, high intensity sunlight resulted in an unexpected thinning of the choroid. These findings have implications regarding the interaction between light exposure, circadian rhythm, and the choroid on myopia.

Characterization of a Chromochloris zofingiensis mutant with enhanced canthaxanthin accumulation

The green alga Chromochloris zofingiensis is able to accumulate value-added ketocarotenoids and represents an alternative producer with industrial production potential. To further understand the biosynthesis of ketocarotenoids, we generated mutants of C. zofingiensis and obtained two (czchy1 and czchy2) with profound changes in carotenoid profile. Both mutants showed a considerably higher level of canthaxanthin than the wild type (WT), with czchy1 being more significant. Clearly, among various stress conditions, czchy1 accumulated the highest level of canthaxanthin under the combination of high light and nitrogen deprivation (HL + ND), which was more than doubled of WT. Prolonged induction of HL + ND allowed canthaxanthin of the alga to reach 2.8 mg g−1 of dry weight, which could be further promoted by the addition of fulvic acid. czchy1 also had higher β-carotene level and lower levels of astaxanthin, lutein and zeaxanthin than WT. Molecular characterization of czchy1 revealed that the β-carotene hydroxylase (CHYb) gene possessed a point mutation and encoded an enzyme with attenuated hydroxylating activity. Besides, in czchy1 as compared to WT, CHYb was transcriptionally down-regulated, β-carotene hydroxylase (BKT1) and lycopene β-cyclase (LCYb) were transcriptionally up-regulated. Therefore, czchy1 likely adopted a multiple strategy combining pull, push and impairment of competing pathway towards boosting canthaxanthin accumulation.

Influence of doses of nitrogen fertilizers and plant growth regulators on generative and vegetative productivity of strawberry (&lt;i&gt;Fragaria×ananassa&lt;/i&gt; Duch.) in a repository

The modern system of nursery management of strawberry should be aimed at the use of adaptive cultivars and clones, allowing to obtain high yields of high-quality products. Optimization of mineral nutrition of plants, the use of plant growth regulators are necessary for the modern management of plant repositories, including strawberry. The study of ways to increase the yield of planting material of strawberry due to the simultaneous inhibition of the formation of peduncles is an urgent task in uterine plantings of the highest quality categories. The purpose of the research: to study the effectiveness of ways to reduce the components of generative productivity and increase the yield of planting material of strawberry garden varieties of short daylight hours and neutral daylight hours. In a field agrochemical experiment with plant growth regulators and doses of nitrogen fertilizer in the Stupinsky district of the Moscow region, on sod-podzolic soils, strawberry cv. Lubava, Tsaritsa, Nashe Podmoscov’e, Polka were studied. Doses of nitrogen fertilizer: N = 80 kg/ha and 120 kg/ha. Plant growth regulators: chlormequat chloride and gibberellic acid (GC3). As a result of the first year of research, it was found that the use of plant growth regulators and an increased dose of nitrogen in the strawberry cultivar of neutral day (Lyubava) contributed to a decrease in generative productivity, but also caused a decrease in the number of outlets. In shortday strawberry plants, a cultivar-specific reaction to fertilizer doses and plant growth regulators was observed, as a result of which it was revealed that the nitrogen dose N 80 kg /ha contributes to an increase in the generative productivity of plants cv. Nashe Podmoskov’e to a greater extent than cv. Polka and cv.Tsaritsa.

Photoperiod effects on guar (Cyamopsis tetragonoloba L.)

Guar (Cyamopsis tetragonoloba), a short-day annual legume plant, is an economically important industrial crop with richness in high valuable guar gum. The photoperiod limits guar’s cultivated region, however, the mechanism of photoperiod effects on guar remains ambiguous. Based on Illumina RNA-seq, PacBio Iso-seq and UPLC-MS for analysis, the current study used different photoperiods to cultivate guar to illustrate the mechanism. The results showed that numerous genes responded to photoperiods differentially, involved in rhythm, flowering, biosynthesis and metabolism pathways. As processing time increased, the number of differentially expressed genes (DEGs) increased from 2518 to 5708. The genes of rhythm, flowering and key transcription factors phyA, GI, ELF3, TOC1, NF-Y and GATA positively responded to short-day, Whereas PRR, FLC, SVP, COL16 and B3 responded negatively to short-day, but positively to long-day. Additionally, the long-day inhibited the expression of genes related to phytohormones metabolism, such as GA synthetic correlation genes GA20ox and GA3ox, and JA synthesis genes AOS and ACX. As a result, the levels of GA and JA reduced, indicating their essential regulatory function in guar flowering. Furthermore, the expressions of the galactomannan synthesis genes were not influenced by photoperiod. In short, the phyA, GI, ELF3, TOC1, NF-Y, GATA, GA20ox and GA3ox were selected as candidate genes for flowering-promotion, while the PRR, FLC, SVP, COL16 and B3 for flowering-repression. This study provides several vital candidate genes for further genetic improvement for obtaining insensitive guar to photoperiod.

Quantifying the role of photoacclimation and self-facilitation for seagrass resilience to light deprivation.

Light gradients are ubiquitous in marine systems as light reduces exponentially with depth. Seagrasses have a set of mechanisms that help them to cope with light stress gradients. Physiological photoacclimation and clonal integration help to maximize light capture and minimize carbon losses. These mechanisms can shape plants minimum light requirements (MLR), which establish critical thresholds for seagrass survival and help us predict ecosystem responses to the alarming reduction in light availability. Using the seagrass Cymodocea nodosa as a case study, we compare the MLR under different carbon model scenarios, which include photoacclimation and/or self-facilitation (based on clonal integration) and that where parameterized with values from field experiments. Physiological photoacclimation conferred plants with increased tolerance to reducing light, approximately halving their MLR from 5-6% surface irradiance (SI) to ≈ 3% SI. In oligotrophic waters, this change in MLR could translate to an increase of several meters in their depth colonization limit. In addition, we show that reduced mortality rates derived from self-facilitation mechanisms (promoted by high biomass) induce bistability of seagrass meadows along the light stress gradient, leading to abrupt shifts and hysteretic behaviors at their deep limit. The results from our models point to (i) the critical role of physiological photoacclimation in conferring greater resistance and ability to recover (i.e., resilience), to seagrasses facing light deprivation and (ii) the importance of self-facilitating reinforcing mechanisms in driving the resilience and recovery of seagrass systems exposed to severe light reduction events.

Synthesis and characterization of a far-red-emitting Sr2ScNbO6: Mn4+ phosphor for short-day plant cultivation

Far-red phosphors with higher thermal stability and exhibit excellent spectral compatibility with the far-red light phytochrome (PFR) absorption spectrum. They are currently a research hotspot and widely applied in plant growth lamps. In this study, we have prepared a Mn4+-activated Sr2ScNbO6 far-red phosphor by using the high temperature solid phase method in air. The strongest excitation center of the Sr2ScNbO6: Mn4+ phosphor was located at 365 nm. Due to the 2Eg→4A2 g transition, this phosphor generates strong deep-red light at 703 nm, which significantly overlaps with the absorption spectrum of plant phytochrome PFR. The variable temperature photoluminescence (PL) emission spectra from 303 K to 503 K confirmed this phosphor possesses relatively good thermal stability. In addition, the concentration quenching effect and the thermal quenching mechanism are studied in detail. The results demonstrate that Sr2ScNbO6: 0.4 % Mn4+ phosphor provides a novel choice for the far-red phosphor required for short-day plant cultivation.

Marine heatwave and reduced light scenarios cause species-specific metabolomic changes in seagrasses under ocean warming.

Climate change and extreme climatic events, such as marine heatwaves (MHWs), are threatening seagrass ecosystems. Metabolomics can be used to gain insight into early stress responses in seagrasses and help to develop targeted management and conservation measures. We used metabolomics to understand the temporal and mechanistic response of leaf metabolism in seagrasses to climate change. Two species, temperate Posidonia australis and tropical Halodule uninervis, were exposed to a combination of future warming, simulated MHW with subsequent recovery period, and light deprivation in a mesocosm experiment. The leaf metabolome of P. australis was altered under MHW exposure at ambient light while H. uninervis was unaffected. Light deprivation impacted both seagrasses, with combined effects of heat and low light causing greater alterations in leaf metabolism. There was no MHW recovery in P. australis. Conversely, the heat-resistant leaf metabolome of H. uninervis showed recovery of sugars and intermediates of the tricarboxylic acid cycle under combined heat and low light exposure, suggesting adaptive strategies to long-term light deprivation. Overall, this research highlights how metabolomics can be used to study the metabolic pathways of seagrasses, identifies early indicators of environmental stress and analyses the effects of environmental factors on plant metabolism and health.

Spectrum of low-intensity screw-in horticultural light-emitting diode lamps influences time to flower and finished quality of long-day ornamental species

Bedding plants with a long-day (LD) flowering requirement constitute a substantial portion of annuals and perennials produced in the United States for spring sales. However, greenhouse production often occurs when the day length is naturally short and not conducive for flower induction of LD plants (LDPs). Thus, growers must create artificial LDs through day-extension, cyclic, or night-interruption (NI) lighting to promote flowering of LDPs. Many low-intensity, screw-in horticultural light-emitting diode (LED) lamps are now commercially available, though their emission spectra vary. Therefore, the objective of our study was to quantify the influence of various commercially available low-intensity screw-in horticultural LED lamps on the flowering and growth responses of LDPs. We grew several obligate and facultative LD annuals under either a 9-h truncated short-day (SD), or a 9-h SD with NI lighting from 2200 to 0200 hr each day. NI treatments consisted of Feit 9-W Non-Dimmable Plant Grow Lights (Feit), General Electric (GE) 10-W Arize™ Greenhouse Pro-Photoperiodic LED Lamps (GE), Philips 13-W GreenPower LED flowering lamp 2.0 s (Philips), or TotalGrow ™ 16-W Pure Flowering 200 Lamps (TotalGrow). Philips and GE lamps hastened flowering of all LDPs studied, while TotalGrow lamps promoted or hastened flowering on a genus-specific basis. Flowering was delayed by up to 11 d under Feit lamps and plants developed more nodes and inflorescences at open flower than the other lighting treatments. Generally, the height of plants within genera were similar regardless of the lighting treatment. However, plants grown under TotalGrow lamps had a larger stem length than those grown under the other lighting treatments as they emitted the highest percentage of FR light. Therefore, greenhouse growers should not base their decision solely on the price of lamps.

Shift in the Light Quality of Night Interruption Affects Flowering and Morphogenesis of Petunia hybrida.

Petunia hybrida Hort. "Easy Wave Pink", a qualitative long-day plant (LDP), was investigated to study the effects of the night interruption light (NIL) provided by light-emitting diodes (LEDs) quality shifting on the morphogenesis, blooming, and transcription of photoreceptor genes. Plants were grown in a closed-type plant factory employing white (W) LEDs at an intensity of 180 μmol·m-2·s-1 PPFD provided for short day (SD, 10 h light, 14 h dark), long day (LD, 16 h light, 8 h dark), or SD with 4 h night interruption (NI) with LEDs at an intensity of 10 μmol·m-2·s-1 PPFD. The NIL quality was shifted from one light spectrum to another after the first 2 h of NI. Light treatments consisting of all possible pairings of W, far-red (Fr), red (R), and blue (B) light were tested. The SD and LD were referenced as the control, while 12 NI treatments involved altering LED NIL qualities, as follows: from R to B (NI-RB), from B to R (NI-BR), from Fr to R (NI-FrR), from R to Fr (NI-RFr), from Fr to B (NI-FrB), from B to Fr (NI-BFr), from B to W (NI-BW), from W to B (NI-WB), from W to Fr (NI-WFr), from Fr to W (NI-FrW), from W to R (NI-WR), and from R to W (NI-RW). The NI-RFr resulted in the longest shoots, while the NI-WR and NI-RW resulted in the shortest shoots. NI-WR, NI-RW, NI-BW, NI-WB, NI-RFr, NI-RB, NI-BR, and LD all exhibited flowering. High-level expressions of photoreceptor genes were confirmed in the NI-RFr, NI-FrR, NI-BFr, NI-RW, and NI-WR treatments. Morphogenesis and blooming were both impacted by the photoperiod. The first NIL had no effects on the flowering or the morphogenesis, but the second NIL had a profound impact on both.

LONG-TERM LIGHT DEPRIVATION AFFECTS DIGESTIVE FUNCTION IN RATS DURING ONTOGENY

The effects of light deprivation on age-related changes in body weight, food and water intake, as well as the activity of digestive enzymes in pancreatic tissues of male rats was studied. Animals were divided into three groups: the first was in standard light conditions (12 h light/12 h dark, control, LD), the second was kept under conditions of long-term light deprivation from the moment of birth (LD/DD), and the third – from the prenatal period (DD/DD). Prolonged keeping of rats under conditions of light deprivation led to disruption of the age-associated dynamics of the studied parameters, at the same time, the detected changes in response to a specific light condition differed depending on the stage of ontogenesis at which its exposure began. Thus, body mass (age 3 and 18 months) and food and water intake (12 months), amylase and lipase activities (18 months) were lower, and protease activities after the end of the stable growth stage (12, 18 and 24 months) were higher in LD/DD-rats than in LD-rats. Significant changes in the studied parameters were observed under DD/DD conditions in 12‑month-old and 18-month-old rats – body mass was the largest, and food and water intake were the lowest compared to LD and LD/DD. In addition, the maximum amylase activity (1 and 6 months) among the studied groups and the higher values of total proteolytic activity during the period of stable growth (6 and 12 months) were found in DD/DD-rats compared to controls. Thus, our results indicate that light deprivation disrupts the ontogenetic development program of the digestive system of mammals.

Long-Term Light Deprivation Affects Digestive Function in Rats in Ontogeny

Long-Term Light Deprivation Affects Digestive Function in Rats in Ontogeny