Light Deprivation Research Articles

Duration of light-emitting diode (LED) supplemental lighting providing far-red radiation during seedling production influences subsequent time to flower of long-day annuals

A low red (R) to far-red (FR) radiation ratio can hasten or promote a flowering response in many long-day plants (LDPs). However, the majority of light-emitting diode (LED) supplemental lighting (SL) fixtures on the market only contain blue (B) and R LEDs and thus, flowering of some LDPs may be delayed if FR radiation is not included in the spectrum. The objectives of this study were to determine 1) the minimum duration of FR radiation needed at the seedling stage to promote subsequent flowering of LDPs and 2) to quantify the response of day-neutral plants to the addition of FR radiation. Upon germination, seedlings of calibrachoa ‘Kabloom Light Pink Blast’ or ‘Kabloom Pink Blast’ (Calibrachoa ×hybrida), impatiens ‘Accent Premium Red’ (Impatiens walleriana), petunia ‘Wave Carmine Velour’ (Petunia ×hybrida), and snapdragon ‘Liberty Classic Yellow’ (Antirrhinum majus), were placed under lighting treatments that included a 9-h truncated short day (SD) or five SL treatments delivering a total photon flux density (TPFD) of 70 μmol m−2 s−1 for up to 16 h day–1 based on an instantaneous threshold. The LED SL treatments defined by their wavebands (photon flux density in μmol m–2 s–1) of B (400–500 nm) and R (600–700 nm) radiation with or without FR (700–800 nm) radiation were B15R40FR15 or B20R50. After 14 or 21 days under B20R50 LED SL, randomly selected seedlings were transferred to B15R40FR15 LED SL where they stayed for the remainder of the experiment for a total of 28 days. Thus, the treatments were 9-h SD, HPS SL, B20R50, B20R50 (21 days) + B15R40FR15 (7 days), B20R50 (14 days) + B15R40FR15 (14 days), and B15R40FR15 (28 days) LED SL. Petunia stem length was not influenced by lighting treatment whereas snapdragon was 17% taller under B20R50 (21 or 14 days) + B15R40FR15 SL (7 or 14 days) and HPS SL compared to B15R40FR15 SL. Additionally, the root dry mass for snapdragon was up to 33% and 22% lower under B20R50 (14 days) + B15R40FR15 SL (14 days) or B15R40FR15 SL, respectively, compared to all other treatments. Time to first visible bud and flower was hastened by B15R40FR15 SL (7–28 days) up to 3 and 8 days for calibrachoa and snapdragon, respectively, compared to HPS or B20R50 SL. Our results indicate that the inclusion of FR radiation via LED SL provided for ≥14 days at the end of the seedling stage can hasten time to flower of LDPs without excessive stem elongation at flower.

A critical role of the soybean evening complex in the control of photoperiod sensitivity and adaptation

Photoperiod sensitivity is a key factor in plant adaptation and crop production. In the short-day plant soybean, adaptation to low latitude environments is provided by mutations at the J locus, which confer extended flowering phase and thereby improve yield. The identity of J as an ortholog of Arabidopsis ELF3, a component of the circadian evening complex (EC), implies that orthologs of other EC components may have similar roles. Here we show that the two soybean homeologs of LUX ARRYTHMO interact with J to form a soybean EC. Characterization of mutants reveals that these genes are highly redundant in function but together are critical for flowering under short day, where the lux1 lux2 double mutant shows extremely late flowering and a massively extended flowering phase. This phenotype exceeds that of any soybean flowering mutant reported to date, and is strongly reminiscent of the "Maryland Mammoth" tobacco mutant that featured in the seminal 1920 study of plant photoperiodism by Garner and Allard [W. W. Garner, H. A. Allard, J. Agric. Res. 18, 553-606 (1920)]. We further demonstrate that the J-LUX complex suppresses transcription of the key flowering repressor E1 and its two homologs via LUX binding sites in their promoters. These results indicate that the EC-E1 interaction has a central role in soybean photoperiod sensitivity, a phenomenon also first described by Garner and Allard. EC and E1 family genes may therefore constitute key targets for customized breeding of soybean varieties with precise flowering time adaptation, either by introgression of natural variation or generation of new mutants by gene editing.

Winter Survival and Second-year Spring Yields of Day-neutral Strawberry Are Influenced by Cultivar and the Presence of Low Tunnels

Day-neutral (DN) strawberry (Fragaria ×ananassa) cultivars have potential to produce high yields in New England and greatly extend the period of regional strawberry production each year. However, DN strawberries have primarily been evaluated as an annual crop in cold climates; thus, winter hardiness and subsequent second-year spring yields are not well understood. Separate DN plantings were established as dormant bare-rooted plants in Durham, NH (U.S. Department of Agriculture hardiness zone 5b) in 2017 and 2018. During their first year of growth and fruit production, plants were grown under one of two cover treatments: a plastic-covered low tunnel or the traditional open field environment (open beds). In November, plants were covered with either straw much (Winter 2017–18) or rowcover (Winter 2018–19) for low-temperature protection during the winter months. In the spring of the second year when winter protection was removed, the same cover treatments (low tunnel or open bed) were re-administered to plants. Plant survival was affected by year and cultivar, with average survival rates of 82% and 98% in Spring 2018 and Spring 2019, respectively. Plant survival ranged from 34% (‘Monterey’) to 99% (‘Aromas’) in 2018, and 92% (‘Albion’) to 100% (‘San Andreas’ and ‘Seascape’) in 2019. Cultivar significantly affected total and marketable yields in both years, and marketable yields ranged from 35.8 to 167.3 g/plant in 2018 and 121.6 to 298.6 g/plant in 2019. The greatest marketable yields were produced by ‘Aromas’, ‘Cabrillo’, ‘San Andreas’, ‘Seascape’, and low-tunnel ‘Sweet Ann’. In 2019, ‘Cabrillo’, ‘San Andreas’, and ‘Seascape’ produced greater marketable yields during the 6-week second-year season than they had during the plants’ first year of fruit production the previous year, which spanned 18 weeks. Low tunnels hastened fruit ripening in the spring and result in earlier fruit harvests, and in 2019, marketable yields were significantly greater under low tunnels for the first 1 to 3 weeks, depending on cultivar. Total and marketable yields were unaffected by low tunnels in 2018, but were significantly greater under low tunnels in 2019. For cultivars in the 2019 experiment, the increase in marketable yield under low tunnels (compared with open beds) ranged from 92.3 to 166.5 g/plant, except for Sweet Ann, for which marketable yields were 256.6 g/plant greater under low tunnels than on open beds. Using a conservative direct market rate of $4.50/lb, the second-year spring yields produced in the present study had a direct market value of between $3899/ha and $95,647/ha, depending on cultivar and year. We demonstrate that it is not only possible to overwinter DN strawberry plants in northern New England, but that the second-year yield may even exceed first-year production. The results from the present study indicate great potential for profitability from an overwintered DN crop.

Light-stabilized FHA2 suppresses miRNA biogenesis through interactions with DCL1 and HYL1

The precise regulation of microRNA (miRNA) biogenesis is crucial for plant development, which requires core microprocessors and many fine tuners to coordinate their miRNA processing activity/specificity in fluctuating cellular environments. During de-etiolation, light triggers a dramatic accumulation of core microprocessors and primary miRNAs (pri-miRNAs) but decreases pri-miRNA processing activity, resulting in relatively constant miRNA levels. The mechanisms underlying these seemingly contradictory regulatory changes remain unclear. In this study, we identified forkhead-associated domain 2 (FHA2) as a light-stabilized suppressor of miRNA biogenesis. We found that FHA2 deficiency increased the level of mature miRNAs, accompanied by a reduction in pri-miRNAs and target mRNAs. Biochemical assays showed that FHA2 associates with the core microprocessors DCL1, HYL1, and SE, forming a complex to suppress their pri-miRNA processing activity. Further analyses revealed that FHA2 promotes HYL1 binding but inhibits the binding of DCL1-PAZ-RNase-RNA-binding domains (DCL1-PRR) to miRNAs, whereas FHA2 does not directly bind to these RNAs. Interestingly, we found that FHA2 protein is unstable in the dark but stabilized by light during de-etiolation. Consistently, disruption of FHA led to defects in light-triggered changes in miRNA expression and reduced the survival rate of de-etiolated seedlings after prolonged light deprivation. Collectively, these data suggest that FHA2 is a novel light-stabilized suppressor of miRNA biogenesis and plays a role in fine-tuning miRNA processing during de-etiolation.

Floral Induction in the Short-Day Plant Chrysanthemum Under Blue and Red Extended Long-Days.

Shorter photoperiod and lower daily light integral (DLI) limit the winter greenhouse production. Extending the photoperiod by supplemental light increases biomass production but inhibits flowering in short-day plants such as Chrysanthemum morifolium. Previously, we reported that flowering in growth-chamber grown chrysanthemum with red (R) and blue (B) LED-light could also be induced in long photoperiods by applying only blue light during the last 4h of 15h long-days. This study investigates the possibility to induce flowering by extending short-days in greenhouses with 4h of blue light. Furthermore, flower induction after 4h of red light extension was tested after short-days RB-LED light in a growth-chamber and after natural solar light in a greenhouse. Plants were grown at 11h of sole source RB light (60:40) in a growth-chamber or solar light in the greenhouse (short-days). Additionally, plants were grown under long-days, which either consisted of short-days as described above extended with 4h of B or R light to long-days or of 15h continuous RB light or natural solar light. Flower initiation and normal capitulum development occurred in the blue-extended long-days in the growth-chamber after 11h of sole source RB, similarly as in short-days. However, when the blue extension was applied after 11h of full-spectrum solar light in a greenhouse, no flower initiation occurred. With red-extended long-days after 11h RB (growth-chamber) flower initiation occurred, but capitulum development was hindered. No flower initiation occurred in red-extended long-days in the greenhouse. These results indicate that multiple components of the daylight spectrum influence different phases in photoperiodic flowering in chrysanthemum in a time-dependent manner. This research shows that smart use of LED-light can open avenues for a more efficient year-round cultivation of chrysanthemum by circumventing the short-day requirement for flowering when applied in emerging vertical farm or plant factories that operate without natural solar light. In current year-round greenhouses’ production, however, extension of the natural solar light during the first 11 h of the photoperiod with either red or blue sole LED light, did inhibit flowering.

Regulation of flowering under short photoperiods based on transcriptomic and metabolomic analysis in Phaseolus vulgaris L.

Common bean (Phaseolus vulgaris L.) is a short-day plant and its flowering time, and consequently, pod yield and quality is influenced by photoperiod. In this study, the photoperiodic-sensitive variety 'Hong jin gou', which flowers 31days (d) earlier in short-day than in long-day, was used as the experimental material. Samples were collected to determine the growth and photosynthetic parameters in each daylength treatment, and transcriptome and metabolome data were conducted. We identified eight genes related to flowering by further screening for differentially expressed genes. These genes function to regulate the biological clock. The combination of differentially expressed genes and metabolites, together with the known regulation network of flowering time and the day-night expression pattern of related genes allow us to speculate on the regulation of flowering time in the common bean and conclude that TIMING OF CAB EXPRESSION1 (TOC1) plays a pivotal role in the network and its upregulation or downregulation causes corresponding changes in the expression of downstream genes. The regulatory network is also influenced by gibberellic acid (GA) and jasmonic acid (JA). These regulatory pathways jointly comprise the flowering regulatory network in common bean.

Characterization of QTL and Environmental Interactions Controlling Flowering Time in Andean Common Bean (Phaseolus vulgaris L.)

Genetic variation for response of flowering time to photoperiod plays an important role in adaptation to environments with different photoperiods, and as consequence is an important contributor to plant productivity and yield. To elucidate the genetic control of flowering time [days to flowering (DTF); growing degree days (GDD)] in common bean, a facultative short-day plant, a quantitative trait loci (QTL) analysis was performed in a recombinant inbred mapping population derived from a cultivated accession and a photoperiod sensitive landrace, grown in different long-day (LD) and short-day (SD) environments by using a multiple-environment QTL model approach. A total of 37 QTL across 17 chromosome regions and 36 QTL-by-QTL interactions were identified for six traits associated with time to flowering and response to photoperiod. The DTF QTL accounted for 28 and 11% on average of the phenotypic variation in the population across LD and SD environments, respectively. Of these, a genomic region on chromosome 4 harboring the major DTF QTL was associated with both flowering time in LD and photoperiod response traits, controlling more than 60% of phenotypic variance, whereas a major QTL on chromosome 9 explained up to 32% of flowering time phenotypic variation in SD. Different epistatic interactions were found in LD and SD environments, and the presence of significant QTL × environment (QE) and epistasis × environment interactions implies that flowering time control may rely on different genes and genetic pathways under inductive and non-inductive conditions. Here, we report the identification of a novel major locus controlling photoperiod sensitivity on chromosome 4, which might interact with other loci for controlling common bean flowering time and photoperiod response. Our results have also demonstrated the importance of these interactions for flowering time control in common bean, and point to the likely complexity of flowering time pathways. This knowledge will help to identify and develop opportunities for adaptation and breeding of this legume crop.

Managing flowering time in Miscanthus and sugarcane to facilitate intra- and intergeneric crosses.

Miscanthus is a close relative of Saccharum and a potentially valuable genetic resource for improving sugarcane. Differences in flowering time within and between Miscanthus and Saccharum hinders intra- and interspecific hybridizations. A series of greenhouse experiments were conducted over three years to determine how to synchronize flowering time of Saccharum and Miscanthus genotypes. We found that day length was an important factor influencing when Miscanthus and Saccharum flowered. Sugarcane could be induced to flower in a central Illinois greenhouse using supplemental lighting to reduce the rate at which days shortened during the autumn and winter to 1 min d-1, which allowed us to synchronize the flowering of some sugarcane genotypes with Miscanthus genotypes primarily from low latitudes. In a complementary growth chamber experiment, we evaluated 33 Miscanthus genotypes, including 28 M. sinensis, 2 M. floridulus, and 3 M. ×giganteus collected from 20.9° S to 44.9° N for response to three day lengths (10 h, 12.5 h, and 15 h). High latitude-adapted M. sinensis flowered mainly under 15 h days, but unexpectedly, short days resulted in short, stocky plants that did not flower; in some cases, flag leaves developed under short days but heading did not occur. In contrast, for M. sinensis and M. floridulus from low latitudes, shorter day lengths typically resulted in earlier flowering, and for some low latitude genotypes, 15 h days resulted in no flowering. However, the highest ratio of reproductive shoots to total number of culms was typically observed for 12.5 h or 15 h days. Latitude of origin was significantly associated with culm length, and the shorter the days, the stronger the relationship. Nearly all entries achieved maximal culm length under the 15 h treatment, but the nearer to the equator an accession originated, the less of a difference in culm length between the short-day treatments and the 15 h day treatment. Under short days, short culms for high-latitude accessions was achieved by different physiological mechanisms for M. sinensis genetic groups from the mainland in comparison to those from Japan; for mainland accessions, the mechanism was reduced internode length, whereas for Japanese accessions the phyllochron under short days was greater than under long days. Thus, for M. sinensis, short days typically hastened floral induction, consistent with the expectations for a facultative short-day plant. However, for high latitude accessions of M. sinensis, days less than 12.5 h also signaled that plants should prepare for winter by producing many short culms with limited elongation and development; moreover, this response was also epistatic to flowering. Thus, to flower M. sinensis that originates from high latitudes synchronously with sugarcane, the former needs day lengths >12.5 h (perhaps as high as 15 h), whereas that the latter needs day lengths <12.5 h.

Visual Forms and Color Palette of Francesca Romana’s Holiness at Tor de’ Specchi in Rome

This article explores the two fresco cycles devoted to Saint Francesca Romana (Francesca Bussa de’ Leoni 1384-1440) in the monastery of Tor de’ Specchi in Rome, founded in 1433. The two cycles, created by different painters twenty years apart, are situated in two adjoining spaces of the monastery. The first, attributed to Antoniazzo Romano, was frescoed in 1468 in a space used for prayer and mass (the Oratorio) and represents her charitable actions, miracles, and celestial visions. The second cycle dated to 1485, in terra verde technique, is situated in the ancient refectory and depicts Francesca Romana’s encounter with demonic creatures. Intriguingly, although Francesca was not canonized until 1608, she is presented as a saint in both cycles. We analyze the two parietal decorations in relation to their sources, the Tractato delli visioni di santa Francesca Romana and Tractato delle bactaglie. These two texts were written in Roman vulgar by Francesca’s confessor, Giovanni Mattiotti, in 1447 to record her divine visions and battles with evil. By focusing on selected scenes from both the cycles, we ascertain how closely the images adhere to Mattiotti’s written accounts or, instead, the autonomy of the images. The aim is to grasp how images and words work together in dialogue and how, thanks to this interaction, the different polarities inherent to holiness can be rendered visual. Indeed, whereas the colorful scenes show aspects of holiness linked to a vivifying dimension - Francesca is welcomed into the heavenly realm in the presence of Christ and the Virgin - the terra verde images depict a noxious dimension characterized by light deprivation, indoor spaces, and opposition to the Devil’s torments. Ultimately, by investigating visual forms, material aspects, and narrative strategies, we unearth how Francesca’s sainthood status has been translated and codified.

Effect of Long-Term Light Deprivation on α-Tocopherol Content in Rats during Ontogeny.

We studied the effect of long-term light deprivation which began at different stages of ontogeny on the content of α-tocopherol in rats during the first 3 months of postnatal development. In the offspring postnatally exposed to constant darkness, the level of α-tocopherol in the liver, kidneys, heart, skeletal muscles, and lungs was significantly decreased at the early stages of postnatal ontogeny (2 weeks and 1 month). In rats kept under constant darkness after birth, the content of α-tocopherol in the lungs was also reduced at the age of 1 month. The modulating effect of light deprivation on the level of α-tocopherol can be associated both with the impact of disturbed circadian rhythms and with increased content of melatonin in the body.

Neuroprotective effect of anthocyanin oligomers demonstrated by ischemic insults and lipid peroxidation

PurposeThe purpose of the present study was to determine whether the flavonoid, anthocyanin oligomers is effective at blunting the negative influence of ischemia/reperfusion to the rat retina in situ and of various insults to a retinal precursor cells (R28) in culture.MethodsR28 in culture were given one of three different insults, light (1000 lux for 2 days), hydrogen peroxide (200 µM H2O2 for 24 hours) or serum deprivation (48 hours). Cell survival and reactive oxygen species (ROS) formation were assayed. Lipid peroxidation assay was used to compare the antioxidant capacity of anthocyanin oligomers. In animal studies, anthocyanin oligomers were administered intraperitoneally just before and after an ischemic insult, and ischemia was delivered by raising the intraocular pressure above the systolic blood pressure(50 min). Retinas were analysed for the localisation of various antigens, and retinal extracts were also analysed for various mRNAs.ResultsIschemia/reperfusion to the retina affected the localisation of Thy‐1 and choline acetyltransferase (ChAT) and the content of various proteins (optic nerve and retina) and mRNAs (retina). Importantly, anthocyanin Oligomers statistically blunted most of the effects induced by ischemia/reperfusion. Only the increase in caspase‐8 caused by ischemia/reperfusion was unaffected by anthocyanin oligomers treatment. Anthocyanin oligomers also attenuated significantly the negative insult of light, hydrogen peroxide and serum withdrawal to R28 cells. In the lipid peroxidation studies, anthocyanin oligomers was also found to be equally effective as EGCG to act as an antioxidant. Significantly, the negative insult of serum withdrawal on R28 cell survival was blunted by anthocyanin oligomers but not by EGCG revealing the different properties of the two flavonoids.ConclusionsOur results demonstrates the powerful antioxidant characteristics of anthocyanin oligomers. Together with anti‐apoptotic effects of anthocyanin oligomers suggest its potential use for the treatment of various ocular diseases such as glaucoma, where oxidative stress has been suggested to be involved in many aspects of pathogenesis.

ONTOGENETIC ASPECTS OF MELATONIN RECEPTORS 1A DENSITY IN THE LATERAL PREOPTIC NUCLEUS OF THE HYPOTHALAMUS UNDER VARIOUS LIGHT CONDITIONS

The aim: To find out density of melatonin receptors 1A in the neurons of the lateral preoptic nucleus of the hypothalamus in mature and old rats under various light conditions. Materials and methods: The study was carried out on 72 albino mature and old rats with light conditions appropriate for the experiment. To find out circadian differences of melatonin receptors 1A the material for the study was taken at 2 p.m. and 2 a.m. Visualization of primary antibodies against melatonin receptors 1A (Abcam) was conducted by means of the polymeric system Dako and diaminobenzidine staining under the microscope Delta Optical Evolution 100. The intensity of staining was assessed on the digital copies of images according to computer microdensitometry method. Results: Immunohistochemical examinations conducted enable to suggest that melatonin receptors 1A in the neurons of the lateral preoptic nucleus of the hypothalamus respond to different light conditions. In particular, intensity of immunohistochemical staining to melatonin receptors 1A under conditions of light deprivation increases both in mature and old rats, but it decreases under conditions of light stimulation. The parameter is higher at 2 a.m. as compared with 2 p.m. Intensity of immunohistochemical staining to melatonin receptors 1A in the neurons of the lateral preoptic nucleus of the hypothalamus is always lower in old rats than in mature ones. Conclusions: Density of melatonin receptors 1A in the neurons of the lateral preoptic nucleus of the hypothalamus is subordinated to the circadian rhythm: it increases at night and decreases in the daytime. At the same time, light stimulation results in disorders of the rhythm and development of desynchronization.

Studi Degreening, Kesegaran, dan Daya Simpan Buah Naga Merah (Hylocereus polyrhizus (Weber) Britton &amp; Rose) untuk Menentukan Kriteria Panen Optimum

Buah naga merah adalah buah non klimakterik dengan lintasan fotosintesis crassulacean acid metabolism. Kematangan optimum ditandai dengan warna kulit buah merah 100%. Tujuan percobaan adalah mempelajari perubahan warna kulit terkait dengan kesegaran dan daya simpan buah naga merah untuk menentukan kriteria panen optimum. Bahan percobaan disiapkan di kebun Sabisa Farm, Sindang Barang, Bogor (60 35’ 16” LS, 1060 46’ BT; elevasi 219 m di atas permukaan laut). Percobaan menggunakan rancangan kelompok lengkap teracak dengan perlakuan 5 taraf umur panen, yaitu 30, 32, 34, 36, dan 38 hari setelah antesis (HSA) dengan 5 ulangan. Hasil percobaan menunjukkan bahwa kulit buah naga merah 30 HSA memiliki skala warna 2 (1-25% merah), buah 32 HSA memiliki skala warna 4 (26-50% merah), dan buah 34, 36, dan 38 HSA telah mencapai skala warna 6 (100% merah) ketika dipanen. Kulit buah 30 HSA memerlukan waktu 6 hari setelah panen (HSP) dan buah 32 HSA memerlukan waktu 3 HSP untuk mencapai warna merah 100%. Pada saat warna merah 100%, buah 30 - 38 HSA memiliki kandungan padatan terlarut total 11.7 hingga 13.5 oBrix yang masih memenuhi standard pemasaran buah naga sebesar 11.0 oBrix. Kandungan asam tertitrasi total menurun, tetapi kandungan vitamin C meningkat dengan meningkatnya umur panen.&#x0D; Kata kunci: CAM, kematangan pascapanen, kesegaran buah, satuan panas, tanaman hari-panjang

Response of medical cannabis (Cannabis sativa L.) genotypes to P supply under long photoperiod: Functional phenotyping and the ionome

Phosphorus (P) is an essential macronutrient required for many central metabolic processes, and is therefore a major factor governing plant development, structure and function. Cannabis is a short-day plant that its' development progression involves a vegetative growth phase under long photoperiod, followed by a reproductive phase under a short photoperiod. The reproductive inflorescence yield potential in cannabis is therefore largely dependent on the morphology and physiological condition of the plants at the vegetative phase. Due to legal restrictions, there is lack of science-based knowledge about cannabis plant science, including mineral nutrition. The present study therefore focused on P nutrition of plants at the vegetative growth phase under long photoperiod. The plants were cultivated in pots in a controlled environment and subjected to 5 levels of P (5, 15, 30, 60, 90 mg L−1). We investigated impact on the ionome, physiological and morphological traits, uptake of nutrients into the plant, translocation to the shoot, and distribution in the plant organs for 2 medicinal cannabis genotypes. Plant biomass production, photosynthesis rate, stomatal conductance, transpiration rate and intercellular CO2 at the vegetative growth phase exceled under 30 mg L−1 P supply. Uptake and translocation of nutrients from root to the shoot was highly influenced by the P treatment. Under excess P supply, most of the plant P accumulated in the roots, and translocation to the shoot was inhibited. Uptake of Mg into the plants, and its' translocation to the shoot was inhibited by P deficiency in both cultivars, and was enhanced by increased P supply. Calcium uptake was increased by P application but translocation to the shoot was inhibited. Zinc retention in roots under P deficiency was found in both varieties. Our results suggest a wide optimum range for P in medicinal cannabis at the vegetative growth stage, with a minimum requirement of 15 mg L−1 P and a recommended application of 30 mg L−1. The functional physiology and ionome profiling revealed genotypic variability in P sensitivity.

In situ Responses of the Eelgrass Zostera marina L. to Water Depth and Light Availability in the Context of Increasing Coastal Water Turbidity: Implications for Conservation and Restoration.

Accelerating losses of seagrass meadows has led to efforts to restore these highly productive and beneficial ecosystems globally. Depth and light availability are critical determinants of seagrass restoration success. Eelgrass (Zostera marina L.) is the dominant seagrass species in the temperate northern hemisphere, but its global distribution has reduced dramatically. The main aims of this study were to determine: (1) the depth limit for Z. marina survival in Ailian Bay, north China, and (2) how light availability affects the growth and recruitment of Z. marina as a basis for identifying a suitable depth range for successful restoration. To achieve these aims, Z. marina shoots were transplanted from a nearby donor site, Swan Lake, to an experimental site, Ailian Bay, and the temporal responses of Z. marina shoots to light availability at water depths ranging from 1 to 8 m were investigated using in situ suspended cultures. Four suspended shoot transplantation experiments were conducted in 4 years. The results showed that the transplanted Z. marina shoots could survive and branch during an annual growth cycle, permanently underwater, at a depth ≤3 m. Due to the local turbidity of the waters in Ailian Bay, a depth of 4 m led to sufficient light deprivation (reduced to 6.48–10.08% of surface irradiance) to negatively affect seagrass shoot density and clonal reproduction. In addition, reproductive shoot density also tended to decline with water depth and light deprivation. Our results indicated that Z. marina population recruitment, through sexual and asexual (clonal growth) reproduction, were negatively affected by increasing water depth and light deprivation. These findings may provide a suitable depth range for the successful restoration of Z. marina in local coastal waters. They may also be applied to the management and restoration of Z. marina globally.

How Supplementary or Night-Interrupting Low-Intensity Blue Light Affects the Flower Induction in Chrysanthemum, A Qualitative Short-Day Plant.

This research examined the effects of the supplementary or night-interrupting (NI) blue (B) light supplied at a low intensity on the flowering, gene expression, and morphogenesis of chrysanthemum, a qualitative short-day plant. White (W) light-emitting diodes (LEDs) were used to provide light with a photosynthetic photon flux density (PPFD) of 180 μmol·m−2·s−1 during the photoperiod to grow the plants in a plant factory. The control group was constructed with plants that were exposed to a 10-h short day (SD10) treatment without any blue light. The B light in this research was used for 4 h to either (1) extend the photoperiod for plants at the end of a 9-h short day (SD) treatment as the sole light source (SD9 + 4B), (2) provide night interruption (NI) to plants in the 13-h long-day (LD) treatment (LD13 + NI − 4B), (3) provide NI to plants in the 10-h SD treatment (SD10 + NI − 4B), or (4) supplement the W LEDs at the end of a 13-h LD treatment (LD13 + 4B). Blue LEDs were used to provide the supplementary/NI light at 10 μmol·m−2·s−1 PPFD. The LD13 + NI − 4B treatment resulted in the greatest plant height, followed by LD13 + 4B. Plants in all treatments flowered. It is noteworthy that despite the fact that chrysanthemum is a qualitative SD plant, chrysanthemum plants flowered when grown in the LD13 + 4B and LD13 + NI − 4B treatments. Plants grown in the LD13 + 4B had the greatest number of flowers. Plants grown in the LD13 + 4B treatment had the highest expression levels of the cryptochrome 1, phytochrome A, and phytochrome B genes. The results of this study indicate that a 4-h supplementation of B light during the photoperiod increases flower bud formation and promotes flowering, and presents a possibility as an alternative method to using blackout curtains in LD seasons to practically induce flowering. The B light application methods to induce flowering in SD plants requires further research.

What is going on with the hormonal control of flowering in plants?

Molecular genetic studies using Arabidopsis thaliana as a model system have overwhelmingly revealed many important molecular mechanisms underlying the control of various biological events, including floral induction in plants. The major genetic pathways of flowering have been characterized in-depth, and include the photoperiod, vernalization, autonomous and gibberellin pathways. In recent years, novel flowering pathways are increasingly being identified. These include age, thermosensory, sugar, stress and hormonal signals to control floral transition. Among them, hormonal control of flowering except the gibberellin pathway is not formally considered a major flowering pathway per se, due to relatively weak and often pleiotropic genetic effects, complex phenotypic variations, including some controversial ones. However, a number of recent studies have suggested that various stress signals may be mediated by hormonal regulation of flowering. In view of molecular diversity in plant kingdoms, this review begins with an assessment of photoperiodic flowering, not in A. thaliana, but in rice (Oryza sativa); rice is a staple crop for human consumption worldwide, and is a model system of short-day plants, cereals and breeding crops. The rice flowering pathway is then compared with that of A. thaliana. This review then aims to update our knowledge on hormonal control of flowering, and integrate it into the entire flowering gene network.

Differences in Inflorescence Numbers and Endogenous Gibberellic Acid Levels in ‘Afterglow’ Bougainvillea

Bougainvillea (Bougainvillea sp.) plant inflorescence number will vary in response to multiple cues such as changes in temperature, water, light intensity, pruning, and photoperiod. Previous research reports that the application of plant growth regulators (PGRs) to bougainvillea grown under varying photoperiods improved inflorescence number, probably as a result of changes in gibberellic acid (GA) levels. There are many bioactive plant GAs, but we chose to investigate differences in gibberellic acid 3 (GA3) levels and inflorescence number in response to the application of ethephon (2-cholorethylphosponic acid) or abscisic acid (ABA) to ‘Afterglow’ bougainvillea (Bougainvillea ×buttiana) grown under 14-hour photoperiod [long-day (LD)] conditions. Plants were 5 inches tall with seven visible lateral nodes and were grown in a greenhouse in 4-inch pots filled with 5-mm coarse aquarium zeolite. Ethephon was applied as a foliar spray at 0.05, 0.07, 0.10, 0.15, or 0.20 mg/plant. ABA was applied as a soil drench at 1, 1.5, 3, 6, 8, or 10 mg/plant. Endogenous levels of GA3 were measured 1 and 48 days after treatment to calculate the change in GA3 (∆GA3). A short day (SD) control of 8 hours was included to measure differences in inflorescence number and ∆GA3 between photoperiods. ‘Afterglow’ plants grown under SD conditions had the greatest decrease in ∆GA3 (–1.09 µg·g–1) over 48 days and the most inflorescences (10.6) compared with LD control plants with a decrease in ∆GA3 of –0.09 µg·g–1 and fewer inflorescences (1.0). Plants grown under LD conditions and treated with 0.05 mg/plant ethephon had inflorescence numbers (9.6) and levels of ∆GA3 (–0.74 µg·g–1) similar to the SD control. As ethephon rate increased to more than 0.05 mg/plant, inflorescence number on LD plants decreased and ∆GA3 increased. Exogenous ABA rates of 1 mg/plant produced inflorescence numbers (1.4) and ∆GA3 (–0.10 µg·g–1) similar to the LD control. As the rate increased, ∆GA3 increased and inflorescence number decreased. Plants treated with ABA rates of 3 mg/plant and more were defoliated and had no inflorescences.

PLANT RESPONSES TO A SHORT-TERM DAILY TEMPERATURE DROP: EFFECT OF PHOTOPERIOD AND COMPARISON OF PLANTS FROM DIFFERENT PHOTOPERIODIC GROUPS

The paper summarizes and systematizes authors’ own and literary data indicating whether or not the plant response to short-term daily temperature drops depends on the photoperiod and photoperiodic group (long-day, neutral, and short-day plants). A daily shortterm temperature drop is used as an alternative to the growth retardants method of plant height control to produce compact vegetable and bedding transplants and ornamental plants. It was previously thought that long-day plants are less responsive to a temperature drop than short-day plants. Based on the analysis of the available data, it was concluded that plant response to a temperature drop does not depend on their belonging to a certain photoperiodic group, but is primarily determined by the conditions of the experiment, namely, the duration of the photoperiod. In particular, the greatest morphogenic effect of a temperature drop is manifested in a short photoperiod. As the photoperiod increases, the effect of a temperature drop gets weaker or is absent. For the effects of a temperature drop to be manifested under long photoperiods, longer temperature decreases are usually required. This is probably due to increased synthesis of gibberellins with an increase in photoperiod, which is characteristic of plants of all photoperiodic groups.

Antidepressant Effect of Blue Light on Depressive Phenotype in Light-Deprived Male Rats.

Blue light has been previously reported to play a salient role in the treatment of seasonal affective disorder. The present study aimed to investigate whether blue light had antidepressant effect on light-deprivation-induced depression model, and the underlying visual neural mechanism. Blue light mitigated depression-like behaviors induced by light deprivation as measured by elevated sucrose preference and reduced immobility time. Blue light enhanced melanopsin expression and light responses in the retina. We also found the upregulation of serotonin and brain derived neurotrophic factor expression in the c-fos-positive areas of rats treated with blue light compared with those maintained in darkness. The species gap between nocturnal albino (Sprague-Dawley rat) and diurnal pigmented animals (human) might have influenced extrapolating data to humans. Blue light has antidepressant effect on light-deprived Sprague-Dawley rats, which might be related to activating the serotonergic system and neurotrophic activity via the retinoraphe and retinoamygdala pathways. Blue light is the effective component of light therapy for treatment of depression.