Hyperspectral imaging and artificial intelligence enhance remote phenotyping of grapevine rootstock influence on whole vine photosynthesis.

Rootstocks are gaining importance in viticulture as a strategy to combat abiotic challenges, as well as enhancing scion physiology. Photosynthetic parameters such as maximum rate of carboxylation of RuBP (Vcmax) and the maximum rate of electron transport driving RuBP regeneration (Jmax) have been identified as ideal targets for potential influence by rootstock and breeding. However, leaf specific direct measurement of these photosynthetic parameters is time consuming, limiting the information scope and the number of individuals that can be screened. This study aims to overcome these limitations by employing hyperspectral imaging combined with artificial intelligence (AI) to predict these key photosynthetic traits at the canopy level. Hyperspectral imaging captures detailed optical properties across a broad range of wavelengths (400 to 1000 nm), enabling use of all wavelengths in a comprehensive analysis of the entire vine's photosynthetic performance (Vcmax and Jmax). Artificial intelligence-based prediction models that blend the strength of deep learning and machine learning were developed using two growing seasons data measured post-solstice at 15 h, 14 h, 13 h and 12 h daylengths for Vitis hybrid 'Marquette' grafted to five commercial rootstocks and 'Marquette' grafted to 'Marquette'. Significant differences in photosynthetic efficiency (Vcmax and Jmax) were noted for both direct and indirect measurements for the six rootstocks, indicating that rootstock genotype and daylength have a significant influence on scion photosynthesis. Evaluation of multiple feature-extraction algorithms indicated the proposed Vitis base model incorporating a 1D-Convolutional neural Network (CNN) had the best prediction performance with a R2 of 0.60 for Vcmax and Jmax. Inclusion of weather and chlorophyll parameters slightly improved model performance for both photosynthetic parameters. Integrating AI with hyperspectral remote phenotyping provides potential for high-throughput whole vine assessment of photosynthetic performance and selection of rootstock genotypes that confer improved photosynthetic performance potential in the scion.

Time-to-growth: photoperiod and photosynthesis make the call.

The intricate regulation of flowering time in response to day length has been extensively shown. A recent study has now revealed a similar mechanism for regulating vegetative growth. Wang et al. observed that plants measure daylength as the duration of photosynthesis and metabolite production to modulate vegetative growth.

Longer days, larger grays: carryover effects of photoperiod and temperature in gray treefrogs, Hyla versicolor.

Environmental conditions like temperature and photoperiod can strongly shape organisms' growth and development. For many ectotherms with complex life cycles, global change will cause their offspring to experience warmer conditions and earlier-season photoperiods, two variables that can induce conflicting responses. We experimentally manipulated photoperiod and temperature during gray treefrog (Hyla versicolor) larval development to examine effects at metamorphosis and during short (10-day) and long (56-day) periods post-metamorphosis. Both early- and late-season photoperiods (April and August) decreased age and size at metamorphosis relative to the average-season (June) photoperiod, while warmer temperatures decreased age but increased size at metamorphosis. Warmer larval temperatures reduced short-term juvenile growth but had no long-term effect. Conversely, photoperiod had no short-term carryover effect, but juveniles from early- and late-season larval photoperiods had lower long-term growth rates than juveniles from the average-season photoperiod. Similar responses to early- and late-season photoperiods may be due to reduced total daylight compared with average-season photoperiods. However, juveniles from late-season photoperiods selected cooler temperatures than early-season juveniles, suggesting that not all effects of photoperiod were due to total light exposure. Our results indicate that despite both temperature and photoperiod affecting metamorphosis, the long-term effects of photoperiod may be much stronger than those of temperature.

Long days induce adaptive secondary dormancy in the seeds of the Mediterranean plant Aethionema arabicum.

Secondary dormancy is an adaptive trait that increases reproductive success by aligning seed germination with permissive conditions for seedling establishment. Aethionema arabicum is an annual plant and member of the Brassicaceae that grows in environments characterized by hot and dry summers. Aethionema arabicum seeds may germinate in early spring when seedling establishment is permissible. We demonstrate that long-day light regimes induce secondary dormancy in the seeds of Aethionema arabicum (CYP accession), repressing germination in summer when seedling establishment is riskier. Characterization of mutants screened for defective secondary dormancy demonstrated that RGL2 mediates repression of genes involved in gibberellin (GA) signaling. Exposure to high temperature alleviates secondary dormancy, restoring germination potential. These data are consistent with the hypothesis that long-day-induced secondary dormancy and its alleviation by high temperatures may be part of an adaptive response limiting germination to conditions permissive for seedling establishment in spring and autumn.

Seasonality in regional brain glucose metabolism.

BACKGROUND: Daylength and the rates of changes in daylength have been associated with seasonal fluctuations in psychiatric symptoms and in cognition and mood in healthy adults. However, variations in human brain glucose metabolism in concordance with seasonal changes remain under explored. METHODS: In this cross-sectional study, we examined seasonal effects on brain glucose metabolism, which we measured using 18F-fluorodeoxyglucose-PET in 97 healthy participants. To maximize the sensitivity of regional effects, we computed relative metabolic measures by normalizing the regional measures to white matter metabolism. Additionally, we explored the role of rest-activity rhythms/sleep-wake activity measured with actigraphy in the seasonal variations of regional brain metabolic activity. RESULTS: We found that seasonal variations of cerebral glucose metabolism differed across brain regions. Glucose metabolism in prefrontal regions increased with longer daylength and with greater day-to-day increases in daylength. The cuneus and olfactory bulb had the maximum and minimum metabolic values around the summer and winter solstice respectively (positively associated with daylength), whereas the temporal lobe, brainstem, and postcentral cortex showed maximum and minimum metabolic values around the spring and autumn equinoxes, respectively (positively associated with faster daylength gain). Longer daylength was associated with greater amplitude and robustness of diurnal activity rhythms suggesting circadian involvement. CONCLUSIONS: The current findings advance our knowledge of seasonal patterns in a key indicator of brain function relevant for mood and cognition. These data could inform treatment interventions for psychiatric symptoms that peak at specific times of the year.

Loss of daylength sensitivity by splice site mutation in Cannabis pseudo-response regulator.

Photoperiod insensitivity (auto-flowering) in drug-type Cannabis sativa circumvents the need for short day (SD) flowering requirements making outdoor cultivation in high latitudes possible. However, the benefits of photoperiod insensitivity are counterbalanced by low cannabinoid content and poor flower quality in auto-flowering genotypes. Despite recent studies in cannabis flowering, a mechanistic understanding of photoperiod insensitivity is still lacking. We used a combination of genome-wide association study and genetic fine-mapping to identify the genetic cause of auto-flowering in cannabis. We then used gene expression analyses and transient transformation assays to characterize flowering time control. Herein, we identify a splice site mutation within circadian clock gene PSEUDO-RESPONSE REGULATOR 37 (CsPRR37) in auto-flowering cannabis. We show that CsPRR37 represses FT expression and its circadian oscillations transition to a less repressive state during SD as compared to long days (LD). We identify several key circadian clock genes whose expression is altered in auto-flowering cannabis, particularly under non-inductive LD. Research into the pervasiveness of this mutation and others affecting flowering time will help elucidate cannabis domestication history and advance cannabis breeding toward a more sustainable outdoor cultivation system.

Longer Photoperiod Substantially Increases Indoor-Grown Cannabis' Yield and Quality: A Study of Two High-THC Cultivars Grown under 12 h vs. 13 h Days.

Indoor-grown Cannabis sativa is commonly transitioned to a 12 h daily photoperiod to promote flowering. However, our previous research has shown that some indoor-grown cannabis cultivars can initiate strong flowering responses under daily photoperiods longer than 12 h. Since longer photoperiods inherently provide higher daily light integrals (DLIs), they may also increase growth and yield. To test this hypothesis, two THC-dominant cannabis cultivars, 'Incredible Milk' (IM) and 'Gorilla Glue' (GG), were grown to commercial maturity at a canopy level PPFD of 540 µmol·m-2·s-1 from white LEDS under 12 h or 13 h daily photoperiods, resulting in DLIs of 23.8 and 25.7 mol·m-2·d-1, respectively. Both treatments were harvested when the plants in the 12 h treatment reached maturity according to established commercial protocols. There was no delay in flowering initiation time in GG, but flowering initiation in IM was delayed by about 1.5 d under 13 h. Stigma browning and trichome ambering also occurred earlier and progressed faster in the 12 h treatment in both cultivars. The vegetative growth of IM plants in the 13 h treatment was greater and more robust. The inflorescence yields were strikingly higher in the 13 h vs. 12 h treatment, i.e., 1.35 times and 1.50 times higher in IM and GG, respectively, which is 4 to 6 times higher than the relative increase in DLIs. The inflorescence concentrations of major cannabinoids in the 13 h treatment were either higher or not different from the 12 h treatment in both cultivars. These results suggest that there may be substantial commercial benefits for using photoperiods longer than 12 h for increasing inflorescence yields without decreasing cannabinoid concentrations in some cannabis cultivars grown in indoor environments.

The nightscape of the Arctic winter shapes the diving behavior of a marine predator.

Predator-prey interactions in marine ecosystems are dynamically influenced by light, as demonstrated by diel vertical migrations of low-trophic level organisms. At high latitudes, the long winter nights can provide foraging opportunities for marine predators targeting vertically migrating prey closer to the surface at night. However, there is limited documentation of such diel patterns in marine predators under extreme light regimes. To address this, we recorded the diving behavior of 17 harbour porpoises just south of the Arctic circle in West Greenland, from summer to winter. Unlike classical diel vertical migration, the porpoises dove 24-37% deeper at night and the frequency of deep dives (> 100 m) increased tenfold as they entered the darkest months. The daily mean depth was negatively correlated with daylength, suggesting an increased diving activity when approaching the polar night. Our findings suggest a light-mediated strategy in which harbour porpoises would either target (i) benthic prey, (ii) pelagic prey migrating seasonally towards the seafloor, or (iii) vertically migrating prey that may be otherwise inaccessible in deeper waters at night, therefore maximizing feeding activity during extended periods of darkness. Extreme light regimes observed at high latitudes are therefore critical in structuring pelagic communities and food webs.

Impact of feed, light and access to manipulable material on tail biting in pigs with intact tails.

BACKGROUND: Tail biting (TB) is a welfare issue with economic consequences due to infections and ill-thrift. This study aimed to reduce tail injuries in a high-performing non-tail-docking pig herd. RESULTS: During eleven years preceding the trial, the annual incidence of tail injuries registered at slaughter in pigs from the herd increased from 3% (equivalent to the national mean) to 10%. It was positively correlated to a high weight gain and negatively correlated to daylight length. The overall incidence of tail injuries during the four years preceding the trial was 9.2% with significant differences between four identically structured buildings for fatteners (I < II < III < IV). The feed was enriched with amino acids, minerals and fibres. The buildings used different illumination strategies, I: standard fluorescent tubes with an invisible flickering light of 30-40% for 14 h daily, II: non-flickering led light for 14 h daily, III (control) and IV: standard fluorescent tubes for 2 h daily. IV had free access to manipulable material (hay-silage), while I-III was offered 100-200 g daily. During the adaptation period (6 months), the incidence of tail injuries decreased significantly in all buildings to a mean of 5.4%. The largest decrease (from 11.4 to 4.3%) was obtained in IV. During the trial period (12 months), the mean incidence of tail injuries decreased in all groups to a mean of 3.0%. There were no differences in treatment incidences of individual pigs due to TB between groups, but the use of enriched pellets due to TB in pens was lowest in II. The low incidence of tail injuries was retained during the post-trial period (6 months) when all buildings used artificial illumination for two hours per day. CONCLUSIONS: The incidence of TB in fast growing non-tail-docked pigs in the herd was successfully reduced by supplementing the feed with amino acids, minerals, vitamins and fibres. Additional manipulable material accelerated that process and non-flickering illumination may have had an impact in preventing TB. The results obtained do not support the need for tail-docking of pigs, provided that the needs of the pigs in terms of feed ingredients, stocking density and access to manipulable materials are fulfilled.

Negative photoperiod induces an increase in the number of ovulations in dairy cattle.

This study sought to examine the impact of negative photoperiod on the incidence of multiple ovulations and pregnancies in dairy cattle. The study population consisted of 5,373 pregnant cows in their third or greater lactation that experienced their first post-partum pregnancy after spontaneous estrus. The positive photoperiod (increasing day-length) extends from December 22 to June 21, whereas the negative photoperiod (decreasing day-length) extends from June 22 to December 21. The odds ratios (ORs) for multiple ovulations and pregnancies in cows that became pregnant during the negative photoperiod and the remaining cows that became pregnant during the positive photoperiod were 1.4 and 1.3 (P < 0.0001), respectively. The ORs for cows that became pregnant ≥ 90 days in milk and the remaining cows that became pregnant < 90 days in milk were 4.3 and 4.1 (P < 0.0001), respectively. No significant differences were detected in the monthly rates of multiple ovulations or pregnancies during positive and negative photoperiods. Thus, the present study demonstrates that the ovarian function in cows is related to changes in day-length, with decreasing day-length being associated with greater multiple ovulation and pregnancy rates. The present study also shows that positive and negative photoperiods exhibit different trends. The results of this study are consistent with a growing body of work demonstrating the effects of photoperiod patterns on the reproductive physiology of cows, with clear implications for twin pregnancy prevention.

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.

Acclimation of circadian rhythms in woodland strawberries (Fragaria vesca L.) to Arctic and mid-latitude photoperiods.

BACKGROUND: Though many abiotic factors are constantly changing, the photoperiod is a predictable factor that enables plants to time many physiological responses. This timing is regulated by the circadian clock, yet little is known about how the clock adapts to the differences in photoperiod between mid-latitudes and high latitudes. The primary objective of this study was to compare how clock gene expression is modified in four woodland strawberry (Fragaria vesca L.) accessions originating from two different populations in Italy (IT1: Tenno, Italy, 45°N, IT4: Salorno, Italy, 46°N) and two in Northern Norway (NOR2: Alta, Norway, 69°N, NOR13: Indre Nordnes, Norway 69°N) when grown under simulated daylength conditions of an Arctic or mid-latitude photoperiod. The second objective was to investigate whether population origin or the difference in photoperiod influenced phytohormone accumulation. RESULTS: The Arctic photoperiod induced lower expression in IT4 and NOR13 for six clock genes (FvLHY, FvRVE8, FvPRR9, FvPRR7, FvPRR5, and FvLUX), in IT1 for three genes (FvLHY, FvPRR9, and FvPRR5) and in NOR2 for one gene (FvPRR9). Free-running rhythms for FvLHY in IT1 and IT4 were higher after the Arctic photoperiod, while the free-running rhythm for FvLUX in IT4 was higher after the mid-latitude photoperiod. IT1 showed significantly higher expression of FvLHY and FvPRR9 than all other accessions, as well as significantly higher expression of the circadian regulated phytohormone, abscisic acid (ABA), but low levels of salicylic acid (SA). NOR13 had significantly higher expression of FvRVE8, FvTOC1, and FvLUX than all other accessions. NOR2 had extremely low levels of auxin (IAA) and high levels of the jasmonate catabolite, hydroxyjasmonic acid (OH-JA). CONCLUSIONS: Our study shows that circadian rhythms in Fragaria vesca are driven by both the experienced photoperiod and genetic factors, while phytohormone levels are primarily determined by specific accessions' genetic factors rather than the experienced photoperiod.

Is Twelve Hours Really the Optimum Photoperiod for Promoting Flowering in Indoor-Grown Cultivars of Cannabis sativa?

Cannabis sativa ("cannabis" hereafter) is a valuable recent addition to Canada's economy with the legalization for recreational use in 2018. The vast majority of indoor cannabis cultivators use a 12-h light/12-h dark photoperiod to promote flowering. To test the hypothesis that robust flowering initiation responses can be promoted in indoor-grown cannabis cultivars under longer photoperiods, clones of ten drug-type cannabis cultivars were grown under six photoperiod treatments. All treatments were based on a standard 24-h day and included 12 h, 12.5 h, 13 h, 13.5 h, 14 h, and 15 h of light. The plants were grown in a growth chamber for 3 to 4 weeks, receiving an approximate light intensity of 360 µmol·m-2·s-1 from white LEDs. Flowering initiation, defined as the appearance of ≥3 pairs of stigmas at the apex of the primary shoot, occurred in all cultivars under all photoperiod treatments up to 14 h. Delays in flowering initiation time under 14 h vs. 12 h ranged from no delay to approximately 4 days, depending on the cultivar. Some cultivars also initiated flowering under 15 h, but floral tissues did not further develop beyond the initiation phase. Harvest metrics of some cultivars responded quadratically with increasing photoperiod, with ideal levels of key flowering parameters varying between 12 h and 13 h. These results suggest there is potential to increase yield in some indoor-grown cannabis cultivars by using longer than 12-h photoperiods during the flowering stage of production. This is attributed to the inherently higher daily light integrals. Indoor cannabis growers should investigate the photoperiod responses of their individual cultivars to determine the optimal photoperiod for producing floral biomass.

An Improved Genome-Wide Association Procedure Explores Gene-Allele Constitutions and Evolutionary Drives of Growth Period Traits in the Global Soybean Germplasm Population.

In soybeans (Glycine max (L.) Merr.), their growth periods, DSF (days of sowing-to-flowering), and DFM (days of flowering-to-maturity) are determined by their required accumulative day-length (ADL) and active temperature (AAT). A sample of 354 soybean varieties from five world eco-regions was tested in four seasons in Nanjing, China. The ADL and AAT of DSF and DFM were calculated from daily day-lengths and temperatures provided by the Nanjing Meteorological Bureau. The improved restricted two-stage multi-locus genome-wide association study using gene-allele sequences as markers (coded GASM-RTM-GWAS) was performed. (i) For DSF and its related ADLDSF and AATDSF, 130-141 genes with 384-406 alleles were explored, and for DFM and its related ADLDFM and AATDFM, 124-135 genes with 362-384 alleles were explored, in a total of six gene-allele systems. DSF shared more ADL and AAT contributions than DFM. (ii) Comparisons between the eco-region gene-allele submatrices indicated that the genetic adaptation from the origin to the geographic sub-regions was characterized by allele emergence (mutation), while genetic expansion from primary maturity group (MG)-sets to early/late MG-sets featured allele exclusion (selection) without allele emergence in addition to inheritance (migration). (iii) Optimal crosses with transgressive segregations in both directions were predicted and recommended for breeding purposes, indicating that allele recombination in soybean is an important evolutionary drive. (iv) Genes of the six traits were mostly trait-specific involved in four categories of 10 groups of biological functions. GASM-RTM-GWAS showed potential in detecting directly causal genes with their alleles, identifying differential trait evolutionary drives, predicting recombination breeding potentials, and revealing population gene networks.

Seasonality of reproduction in an ever-wet lowland tropical forest in Amazonian Ecuador.

Flowering and fruiting phenology have been infrequently studied in the ever-wet hyperdiverse lowland forests of northwestern equatorial Amazonía. These Neotropical forests are typically called aseasonal with reference to climate because they are ever-wet, and it is often assumed they are also aseasonal with respect to phenology. The physiological limits to plant reproduction imposed by water and light availability are difficult to disentangle in seasonal forests because these variables are often temporally correlated, and both are rarely studied together, challenging our understanding of their relative importance as drivers of reproduction. Here we report on the first long-term study (18 years) of flowering and fruiting phenology in a diverse equatorial forest, Yasuní in eastern Ecuador, and the first to include a full suite of on-site monthly climate data. Using twice monthly censuses of 200 traps and >1000 species, we determined whether reproduction at Yasuní is seasonal at the community and species levels and analyzed the relationships between environmental variables and phenology. We also tested the hypothesis that seasonality in phenology, if present, is driven primarily by irradiance. Both the community- and species-level measures demonstrated strong reproductive seasonality at Yasuní. Flowering peaked in September-November and fruiting peaked in March-April, with a strong annual signal for both phenophases. Irradiance and rainfall were also highly seasonal, even though no month on average experienced drought (a month with <100 mm rainfall). Flowering was positively correlated with current or near-current irradiance, supporting our hypothesis that the extra energy available during the period of peak irradiance drives the seasonality of flowering at Yasuní. As Yasuní is representative of lowland ever-wet equatorial forests of northwestern Amazonía, we expect that reproductive phenology will be strongly seasonal throughout this region.

La fenología de floración y fructificación ha sido poco estudiada en los bosques bajos, lluviosos e hiperdiversos de la Amazonía noroccidental. Estos bosques neotropicales son típicamente llamados no estacionales debido a su clima siempre lluvioso y se asume que son no estacionales con respecto a la fenología. Los límites fisiológicos a la reproducción de las plantas impuestos por la disponibilidad de agua y luz en estos bosques son difíciles de desentrañar debido a que estas variables están a menudo correlacionadas temporalmente y las dos se estudian usualmente por separado, lo que desafía nuestra comprensión de su importancia relativa como desencadenantes de la reproducción. Este es el primer estudio de largo plazo (18 años) de la fenología de floración y fructificación en un bosque hiperdiverso de la Amazonía noroccidental ecuatorial, Yasuní, ubicado al este de Ecuador, y el primero en incluir un completo set de datos climáticos mensuales. Usando censos quincenales de 200 trampas y > 1000 especies, examinamos si la reproducción en Yasuní es estacional a nivel de comunidad y de especies y analizamos las relaciones de las variables ambientales con la fenología. También nos interesaba probar si la estacionalidad en la fenología, en caso de que esté presente está causada por la irradiancia. Tanto a nivel de comunidad como de especies, los datos demuestran una fuerte estacionalidad reproductiva en Yasuní. La floración alcanzó un máximo en septiembre-noviembre y la fructificación alcanzó un máximo en marzo-abril, con una fuerte y consistente señal anual en las dos fenofases. A su vez, la irradiancia y la lluvia fueron también marcadamente estacionales, aunque ningún mes en promedio experimentó sequía (i.e. <100 mm de lluvia). La floración fue positivamente correlacionada con la irradiación, apoyando nuestra hipótesis de que la energía extra disponible durante los periodos de mayor irradiación causa la estacionalidad de la floración en Yasuní. Debido a que Yasuní representa a los bosques ecuatoriales lluviosos de tierras bajas de la Amazonía noroccidental, esperamos que la fenología reproductiva sea fuertemente estacional a lo largo de esta región.

The Influence of Photoperiod, Intake of Polyunsaturated Fatty Acids, and Food Availability on Seasonal Acclimatization in Red Deer (Cervus elaphus).

Hypometabolism and hypothermia are common reactions of birds and mammals to cope with harsh winter conditions. In small mammals, the occurrence of hibernation and daily torpor is entrained by photoperiod, and the magnitude of hypometabolism and decrease of body temperature (Tb) is influenced by the dietary supply of essential polyunsaturated fatty acids. We investigated whether similar effects exist in a non-hibernating large mammal, the red deer (Cervus elaphus). We fed adult females with pellets enriched with either linoleic acid (LA) or α-linolenic acid (ALA) during alternating periods of ad libitum and restricted feeding in a cross-over experimental design. Further, we scrutinized the role of photoperiod for physiological and behavioral seasonal changes by manipulating the amount of circulating melatonin. The deer were equipped with data loggers recording heart rate, core and peripheral Tb, and locomotor activity. Further, we regularly weighed the animals and measured their daily intake of food pellets. All physiological and behavioral parameters measured varied seasonally, with amplitudes exacerbated by restricted feeding, but with only few and inconsistent effects of supplementation with LA or ALA. Administering melatonin around the summer solstice caused a change into the winter phenotype weeks ahead of time in all traits measured. We conclude that red deer reduce energy expenditure for thermoregulation upon short daylength, a reaction amplified by food restriction.

Sense in sensitivity: difference in the meaning of photoperiod insensitivity between wheat and barley.

The description of long photoperiod sensitivity in wheat and barley is a cause of confusion for researchers working with these crops, usually accustomed to free exchange of physiological and genetic knowledge of such similar crops. Indeed, wheat and barley scientists customarily quote studies of either crop species when researching one of them. Among their numerous similarities, the main gene controlling the long photoperiod sensitivity is the same in both crops (PPD1; PPD-H1 in barley and PPD-D1 in hexaploid wheat). However, the photoperiod responses are different: (i) the main dominant allele inducing shorter time to anthesis is the insensitive allele in wheat (Ppd-D1a) but the sensitive allele in barley (Ppd-H1) (i.e. sensitivity to photoperiod produces opposite effects on time to heading in wheat and barley); (ii) the main 'insensitive' allele in wheat, Ppd-D1a, does confer insensitivity, whilst that of barley reduces the sensitivity but still responds to photoperiod. The different behaviour of PPD1 genes in wheat and barley is put in a common framework based on the similarities and differences of the molecular bases of their mutations, which include polymorphism at gene expression levels, copy number variation, and sequence of coding regions. This common perspective sheds light on a source of confusion for cereal researchers, and prompts us to recommend accounting for the photoperiod sensitivity status of the plant materials when conducting research on genetic control of phenology. Finally, we provide advice to facilitate the management of natural PPD1 diversity in breeding programmes and suggest targets for further modification through gene editing, based on mutual knowledge on the two crops.

Photoperiod Genes Contribute to Daylength-Sensing and Breeding in Rice.

Rice (Oryza sativa L.), one of the most important food crops worldwide, is a facultative short-day (SD) plant in which flowering is modulated by seasonal and temperature cues. The photoperiodic molecular network is the core network for regulating flowering in rice, and is composed of photoreceptors, a circadian clock, a photoperiodic flowering core module, and florigen genes. The Hd1-DTH8-Ghd7-PRR37 module, a photoperiodic flowering core module, improves the latitude adaptation through mediating the multiple daylength-sensing processes in rice. However, how the other photoperiod-related genes regulate daylength-sensing and latitude adaptation remains largely unknown. Here, we determined that mutations in the photoreceptor and circadian clock genes can generate different daylength-sensing processes. Furthermore, we measured the yield-related traits in various mutants, including the main panicle length, grains per panicle, seed-setting rate, hundred-grain weight, and yield per panicle. Our results showed that the prr37, elf3-1 and ehd1 mutants can change the daylength-sensing processes and exhibit longer main panicle lengths and more grains per panicle. Hence, the PRR37, ELF3-1 and Ehd1 locus has excellent potential for latitude adaptation and production improvement in rice breeding. In summary, this study systematically explored how vital elements of the photoperiod network regulate daylength sensing and yield traits, providing critical information for their breeding applications.

New Horizons in Plant Photoperiodism.

Photoperiod-measuring mechanisms allow organisms to anticipate seasonal changes to align reproduction and growth with appropriate times of the year. This review provides historical and modern context to studies of plant photoperiodism. We describe how studies of photoperiodic flowering in plants led to the first theoretical models of photoperiod-measuring mechanisms in any organism. We discuss how more recent molecular genetic studies in Arabidopsis and rice have revisited these concepts. We then discuss how photoperiod transcriptomics provides new lessons about photoperiodic gene regulatory networks and the discovery of noncanonical photoperiod-measuring systems housed in metabolic networks of plants. This leads to an examination of nonflowering developmental processes controlled by photoperiod, including metabolism and growth. Finally, we highlight the importance of understanding photoperiodism in the context of climate change, delving into the rapid latitudinal migration of plant species and the potential role of photoperiod-measuring systems in generating photic barriers during migration.

Gradual daylength sensing coupled with optimum cropping modes enhances multi-latitude adaptation of rice and maize.

To expand crop planting areas, reestablishment of crop latitude adaptation based on genetic variation in photoperiodic genes can be performed, but it is quite time consuming. By contrast, a crop variety that already exhibits multi-latitude adaptation has the potential to increase its planting areas to be more widely and quickly available. However, the importance and potential of multi-latitude adaptation of crop varieties have not been systematically described. Here, combining daylength-sensing data with the cropping system of elite rice and maize varieties, we found that varieties with gradual daylength sensing coupled with optimum cropping modes have an enhanced capacity for multi-latitude adaptation in China. Furthermore, this multi-latitude adaptation expanded their planting areas and indirectly improved China's nationwide rice and maize unit yield. Thus, coupling the daylength-sensing process with optimum cropping modes to enhance latitude adaptability of excellent varieties represents an exciting approach for deploying crop varieties with the potential to expand their planting areas and quickly improve nationwide crop unit yield in developing countries.