Attainment of reproductive competence, phase transition, and quantification of juvenility in mutant genetic screens

Plant development between seedling emergence and flowering is characterized by a series of successive qualitative phases: (1) a post embryonic photoperiodinsensitive phase, during which plants are insensitive to photoperiod; (2) a photoperiod- sensitive inductive phase, in which plants require a number of short day (SD) or long day (LD) inductive cycles, depending on their age for rapid flowering, and (3) a photoperiod-insensitive post-inductive phase, in which plant development is no longer influenced by photoperiod (Figure 1; Matsoukas et al., 2013)

Florigens and antiflorigens: a molecular genetic understanding

Florigens, the leaf-derived signals that initiate flowering, have been described as mysterious, elusive and the Holy Grail of plant biology.Comment: 16 pages, 3 figures, 2 tables, journal. arXiv admin note: text overlap with arXiv:1210.660

Genetic and physiological analysis of juvenility in plants

One of the distinguishable plant developmental events is the transition from the vegetative to reproductive phase (RP) of development. This stage is preceded by the juvenile to adult transition within the vegetative phase. During the juvenile vegetative phase (JVP) plants are incompetent to initiate reproductive development and are effectively insensitive to photoperiod. With the change to the adult vegetative phase (AVP), plants attain competence to respond to floral inducers, which is required for the transition to the RP. This study exploits Antirrhinum and Arabidopsis as model systems to understand the genetic and environmental factors that regulate floral incompetence during the JVP. Determinants such as irradiance and [CO2] were found to be key modifiers of the JVP. A relationship between photosynthetic assimilate levels and vegetative phase transition was revealed by analysis of carbohydrates in plants at defined developmental stages. Experimental data suggest that carbohydrate levels may be required to reach a specific threshold before plants undergo the transition from a juvenile to an adult phase of vegetative growth. This may be necessary in order to sustain a steady supply of sugars for sufficient bulk flow from the leaves to the shoot apical meristem (SAM), via the phloem, to enable delivery of florigen, which thus renders the SAM competent to flower. Determination of the JVP in Arabidopsis mutants impaired in different genetic pathways has shown that multiple inputs influence the timing of the vegetative phase transition. Carbohydrates have been demonstrated to be involved possibly through their function as nutrients or signals or by their interaction with hormones. Physiological analysis of flowering time mutants has shown that a variety of signals act to promote and enable the juvenile to adult phase transition that involves both floral activators and repressors

Genetic and physiological analysis of juvenility in plants

One of the distinguishable plant developmental events is the transition from the vegetative to reproductive phase (RP) of development. This stage is preceded by the juvenile to adult transition within the vegetative phase. During the juvenile vegetative phase (JVP) plants are incompetent to initiate reproductive development and are effectively insensitive to photoperiod. With the change to the adult vegetative phase (AVP), plants attain competence to respond to floral inducers, which is required for the transition to the RP. This study exploits Antirrhinum and Arabidopsis as model systems to understand the genetic and environmental factors that regulate floral incompetence during the JVP. Determinants such as irradiance and [CO2] were found to be key modifiers of the JVP. A relationship between photosynthetic assimilate levels and vegetative phase transition was revealed by analysis of carbohydrates in plants at defined developmental stages. Experimental data suggest that carbohydrate levels may be required to reach a specific threshold before plants undergo the transition from a juvenile to an adult phase of vegetative growth. This may be necessary in order to sustain a steady supply of sugars for sufficient bulk flow from the leaves to the shoot apical meristem (SAM), via the phloem, to enable delivery of florigen, which thus renders the SAM competent to flower. Determination of the JVP in Arabidopsis mutants impaired in different genetic pathways has shown that multiple inputs influence the timing of the vegetative phase transition. Carbohydrates have been demonstrated to be involved possibly through their function as nutrients or signals or by their interaction with hormones. Physiological analysis of flowering time mutants has shown that a variety of signals act to promote and enable the juvenile to adult phase transition that involves both floral activators and repressors.EThOS - Electronic Theses Online ServiceGreek State Scholarship FoundationWarwick Horticulture Research InternationalUniversity of WarwickGCRI TrustSociety for Experimental Biology (Great Britain)Great Britain. Dept. for Environment, Food & Rural Affairs (DEFRA)GBUnited Kingdo

ENSO surface shortwave radiation forcing over the tropical Pacific

International audienceWe have studied the spatial and temporal variation of the downward shortwave radiation (DSR) at the surface of the Earth during ENSO events for a 21-year period over the tropical and subtropical Pacific Ocean (40° S?40° N, 90° E?75° W). The fluxes were computed using a deterministic model for atmospheric radiation transfer, along with satellite data from the ISCCP-D2 database, reanalysis data from NCEP/NCAR for the key atmospheric and surface input parameters, and aerosol parameters from GADS (acronyms explained in main text). A clear anti-correlation was found between the downward shortwave radiation anomaly (DSR-A) time-series, in the region 7° S?5° N 160° E-160° W located west of the Niño-3.4 region, and the Niño-3.4 index time-series. In this region where the highest in absolute value DSR anomalies are observed, the mean DSR anomaly values range from ?45 Wm?2 during El Niño episodes to +40 Wm?2 during La Niña events. Within the Niño-3.4 region no significant DSR anomalies are observed during the cold ENSO phase in contrast to the warm ENSO phase. A high correlation was also found over the western Pacific (10° S?5° N, 120?140° E), where the mean DSR anomaly values range from +20 Wm?2 to ?20 Wm?2 during El Niño and La Niña episodes, respectively. There is also convincing evidence that the time series of the mean downward shortwave radiation anomaly in the north subtropical Pacific region 7?15° N 150?170° E, precedes the Niño-3.4 index time-series by about 7 months. Thus, the downward shortwave radiation anomaly is a complementary index to the SST anomaly for the study of ENSO events and can be used to assess whether or not El Niño or La Niña conditions prevail

Ten-year global distribution of downwelling longwave radiation

International audienceDownwelling longwave fluxes, DLFs, have been derived for each month over a ten year period (1984?1993), on a global scale with a resolution of 2.5° × 2.5°. The fluxes were computed using a deterministic model for atmospheric radiation transfer, along with satellite and reanalysis data for the key atmospheric input parameters, i.e. cloud properties, and specific humidity and temperature profiles. The cloud climatologies were taken from the latest released and improved International Satellite Climatology Project D2 series. Specific humidity and temperature vertical profiles were taken from three different reanalysis datasets; NCEP/NCAR, GEOS, and ECMWF (acronyms explained in main text). DLFs were computed for each reanalysis dataset, with differences reaching values as high as 30 Wm?2 in specific regions, particularly over high altitude areas and deserts. However, globally, the agreement is good, with the rms of the difference between the DLFs derived from the different reanalysis datasets ranging from 5 to 7 Wm?2. The results are presented as geographical distributions and as time series of hemispheric and global averages. The DLF time series based on the different reanalysis datasets show similar seasonal and inter-annual variations, and similar anomalies related to the 86/87 El Niño and 89/90 La Niña events. The global ten-year average of the DLF was found to be between 342.2 Wm?2 and 344.3 Wm?2, depending on the dataset. We also conducted a detailed sensitivity analysis of the calculated DLFs to the key input data. Plots are given that can be used to obtain a quick assessment of the sensitivity of the DLF to each of the three key climatic quantities, for specific climatic conditions corresponding to different regions of the globe. Our model downwelling fluxes are validated against available data from ground-based stations distributed over the globe, as given by the Baseline Surface Radiation Network. There is a negative bias of the model fluxes when compared against BSRN fluxes, ranging from ?7 to ?9 Wm?2, mostly caused by low cloud amount differences between the station and satellite measurements, particularly in cold climates. Finally, we compare our model results with those of other deterministic models and general circulation models