Determining the Optimum Night Length for Flower Development in a Modern Poinsettia Cultivar

The effect of night length (NL) on the flower development of poinsettia (Euphorbia pulcherrima Willd. ex Klotzsch) ‘Prestige Red’ was evaluated. Flower initiation occurred by subjecting plants to a 14-hour NL for 10 or 17 days, termed short-day (SD) treatments, and then transferring the plants to each of four NL treatments (11, 12, 13, or 14 hours) to observe the effects of NL on flower development. The plants grown continuously with the 14-h NL treatment were the control group. The timing of first color, visible bud, and anthesis were recorded during flower development, and bract and leaf data were collected at anthesis. Leaf number was unaffected by the SD or NL treatments, suggesting that flower initiation occurred during the 10-day SD treatment before the start of NL treatments; thus, the NL treatments only affected flower development. The timing of first color and visible bud were significantly delayed with the 10-day SD × 11-hour NL treatment relative to the 14-hour NL control; however, first color and visible bud were not delayed with the 17-day SD × 11-hour NL treatment. The 11-hour NL treatment resulted in fewer plants reaching anthesis, and these plants had fewer stem bracts and less bract color development compared with the 12-hour, 13-hour, and 14-hour NL treatments. Therefore, an 11-hour NL is suboptimal for flower development; nonetheless, significant development did occur. The 12-hour NL resulted in less color development than the 13-hour and 14-hour NL treatments in the lowest stem bract positions, but the plants had a commercially acceptable appearance. These results demonstrate that minimal differences in flower development occur with NL ≥12 hours, but that optimal development required NL ≥13 hours.

Optimizing Photoperiod Switch to Maximize Floral Biomass and Cannabinoid Yield in Cannabis sativa L.: A Meta-Analytic Quantile Regression Approach

Cannabis sativa L. is an annual, short-day plant, such that long-day lighting promotes vegetative growth while short-day lighting induces flowering. To date, there has been no substantial investigation on how the switch between these photoperiods influences yield of C. sativa despite the tight correlation that plant size and floral biomass have with the timing of photoperiod switches in indoor growing facilities worldwide. Moreover, there are only casual predictions around how the timing of the photoperiodic switch may affect the production of secondary metabolites, like cannabinoids. Here we use a meta-analytic approach to determine when growers should switch photoperiods to optimize C. sativa floral biomass and cannabinoid content. To this end, we searched through ISI Web of Science for peer-reviewed publications of C. sativa that reported experimental photoperiod durations and results containing cannabinoid concentrations and/or floral biomass, then from 26 studies, we estimated the relationship between photoperiod and yield using quantile regression. Floral biomass was maximized when the long daylength photoperiod was minimized (i.e., 14 days), while THC and CBD potency was maximized under long day length photoperiod for ~42 and 49–50 days, respectively. Our work reveals a yield trade-off in C. sativa between cannabinoid concentration and floral biomass where more time spent under long-day lighting maximizes cannabinoid content and less time spent under long-day lighting maximizes floral biomass. Growers should carefully consider the length of long-day lighting exposure as it can be used as a tool to maximize desired yield outcomes.

Phenylalanine Suppresses Cell Death Caused by Loss of Fumarylacetoacetate Hydrolase in Arabidopsis

Fumarylacetoacetate hydrolase (FAH) catalyzes the final step of Tyrosine (Tyr) degradation pathway essential to animals and the deficiency of FAH causes an inborn lethal disease. In plants, a role of this pathway was unknown until we found that mutation of Short-day Sensitive Cell Death1 (SSCD1), encoding Arabidopsis FAH, results in cell death under short day. Phenylalanine (Phe) could be converted to Tyr and then degraded in both animals and plants. Phe ingestion in animals worsens the disease caused by FAH defect. However, in this study we found that Phe represses cell death caused by FAH defect in plants. Phe treatment promoted chlorophyll biosynthesis and suppressed the up‑regulation of reactive oxygen species marker genes in the sscd1 mutant. Furthermore, the repression of sscd1 cell death by Phe could be reduced by α-aminooxi-β-phenylpropionic acid but increased by methyl jasmonate, which inhibits or activates Phe ammonia-lyase catalyzing the first step of phenylpropanoid pathway, respectively. In addition, we found that jasmonate signaling up‑regulates Phe ammonia-lyase 1 and mediates the methyl jasmonate enhanced repression of sscd1 cell death by Phe. These results uncovered the relation between chlorophyll biosynthesis, phenylpropanoid pathway and jasmonate signaling in regulating the cell death resulting from loss of FAH in plants.

Testis development in the Japanese eel is affected by photic signals through melatonin secretion

Objective According to reported spawning characteristics of Japanese eel, Anguilla japonica, which exhibit spawning and migration patterns that are synchronized with lunar cycles and photoperiod, we hypothesized that a close association exists between specific photic signals (daylight, daylength, and moonlight) and endocrinological regulation. Given the photic control in melatonin secretion, this hypothesis was tested by investigating whether melatonin signals act as mediators relaying photic signals during testis development in the eel. Methods We examined changes in melatonin-secretion patterns using time-resolved fluorescence immunoassays in sexually immature and mature male Japanese eels under the condition of a new moon (NM) and a full moon (FM). Results The eye and plasma melatonin levels exhibited a nocturnal pattern under a 12-h light: dark cycle (12L12D) or under constant darkness (DD), but not with constant light (LL). Eye melatonin levels were similar under the 12L12D and short-day (9L15D) conditions. In the long-day condition (15L9D), secreted plasma melatonin levels were stable, whereas short-day melatonin secretion began when darkness commenced. Sexual maturation began at 8 weeks following intraperitoneal injection of human chorionic gonadotropin (hCG), and NM exposure led to significantly higher eye and plasma melatonin levels compared with those detected under FM exposure.

The Role of Endogenous Carbon Monoxide (CO) in the Functioning of Biological Clocks in Pig and Wild Boar Hybrids During Long- and Short-day Seasons

Mature males of a wild boar-pig crossbreed during long- and short-day seasons were used for the study, which demonstrated that the chemical light carrier CO regulates the expression of biological clock genes in the hypothalamus (preoptic area - POA and dorsal part of hypothalamus - DH) via humoral pathways. Autologous blood with experimentally elevated concentrations of endogenous CO (using lamps with white light-emitting diodes) was infused into the ophthalmic venous sinus via the right dorsal nasal vein.The results showed that elevated endogenous CO levels through blood irradiation induced changes in gene expression involved in the functioning of the main biological clock. Changes in the expression of the transcription factors Bmal1, Clock and Npas2 had a similar pattern in both structures, where a very large decrease in gene expression was shown after exposure to elevated endogenous CO levels. The changes in the gene expression of PER 1-2, CRY 1-2, REV-ERB α-β and ROR β are not the same for both POA and DH hypothalamic structures, indicating that both structures respond differently to the received humoral signal.The obtained results indicate that CO is a chemical light molecule whose production in organisms depends on the amount of light. An adequate amount of light is an essential factor for the proper functioning of the main biological clock.

The Role of Endogenous Carbon Monoxide (CO) on Functioning of Biological Clock in Pig and Wild Boar Hybrid During Long and Short Day Season

Bacground: The master biological clock (pacemaker) is located in the suprachiasmatic nuclei (SCN) of the preoptic part of the hypothalamus (POA) and makes organisms adjust to the rhythms, both annual and circadian. Intrinsic pacemaker function is based on the 24-hour oscillator of the transcription factor genes Bmal1/Clock or its paralog Npas2 in which an E-box-bound heterodimeric transcription factor drives the expression of Per 1-2, Cry 1-2 and Rev-erb α-β (NR1D1 and NR1D2) genes. The main factor that influences the functioning of this clock rhythm is the light signal reaching the SCN from the retina via the neural pathway, the so-called non-forming image signal. On the other hand, endogenous carbon monoxide (CO) whose formation and availability depends on the amount of light is a chemical signal delivered through the humoral pathway independently of the neural signal. The aim of this experiment was to demonstrate that chemical light carrier CO, regulates the expression of biological clock genes via humoral pathways. Mature males of a wild boar-pig crossbreed, during long and short day season, were used for the study. Autologous blood with experimentally elevated concentrations of endogenous CO (using lamps with white light-emitting diodes) was infused into ophthalmic venous sinus via the right dorsal nasal vein.Results: The results showed that elevated endogenous CO levels through blood irradiation induces changes in genes expressioninvolved in functioning of the major biological clock. Changes in the expression of the transcription factors Bmal1, Clock and Npas2 have a similar pattern in both structures where a very large decrease in gene expression was shown after exposure to elevated endogenous CO levels. The changes in the gene expression of Per 1-2, Cry 1-2, and Rev-erb α-β and Ror β are not the same for both POA and DH structures indicating that both structures respond differently to the received humoral signal.Conclusion: Obtained results indicate that CO is a chemical light molecule whose production in organism depends on the amount of light. An adequate amount of light is an essential factor for the proper functioning of the internal biological clock which is a regulator of many important physiological processes.