Abstract James Webb Space Telescope (JWST) observations have been demonstrated to be efficient in detecting multiple stellar populations in globular clusters (GCs) in the low-mass regime of M dwarfs. ...We present an overview, and first results, of different projects that can be explored by using the JWST observations gathered under program GO2560 for 47 Tucanae, the first program entirely devoted to the investigation of multiple populations in very-low-mass stars, which includes spectroscopic data for the faintest GC stars for which spectra are available. Our color–magnitude diagram (CMD) shows some substructures for ultracool stars, including gaps and breaks in slope. In particular, we observe both a gap and a minimum in the F322W2 luminosity function less than 1 mag apart, and discuss which it could be associated with the H-burning limit. We detect stars fainter than this minimum, very likely brown dwarfs. We corroborate the ubiquity of the multiple populations across different masses, from ∼0.1 M ⊙ up to red giants (∼0.8 M ⊙ ). The oxygen range inferred for the M dwarfs, both from the CMD and from the spectra of two M dwarfs associated with different populations, is similar to that observed for giants. We have not detected any difference between the fractions of stars in distinct populations across stellar masses ≳ 0.1 M ⊙ . This work demonstrates the JWST's capability in uncovering multiple populations within M dwarfs and illustrates the possibility to analyze very-low-mass stars in GCs approaching the H-burning limit and the brown-dwarf sequence.
Understanding the formation of multiple populations in globular clusters (GCs) represents a challenge for stellar population studies. Nevertheless, the outermost GC regions, which may retain ...information of the initial configuration of the multiple populations, are poorly studied. We use synthetic spectra that account for the chemical compositions of first- and second-population (1P, 2P) stars of 47 Tucanae to identify the spectral regions that are sensitive to its multiple populations. Hence, we defined new photometric bands that are efficient to disentangle 1P and 2P giant stars from Gaia XP spectra. To test these new filters, we constructed the pseudo two-color diagrams dubbed chromosome maps (ChMs) and identified for the first time, 1P and 2P stars in the outermost cluster regions of 47 Tucanae and outside the tidal radius. We constructed similar diagrams for NGC3201, NGC6121, NGC6752, and NGC6397, thus exploring GCs with different metallicities. The ChMs allowed us to clearly disentangle 1P and 2P stars in the external regions of all clusters, with the exception of the metal-poor NGC6397. Our findings, together with literature results from more-internal regions, show that the 2P stars of 47 Tucanae and NGC 3201 are more-centrally concentrated than the 1P, whereas the multiple populations of NGC 6121, and NGC 6752 share the same radial distributions. These radial behaviors are consistent with the GC formation scenarios where 2P stars originate in the central regions. Noticeably, results on NGC 3201 are in tension with the conclusion from recent work that its 1P is more centrally concentrated than the 2P and might form with more central concentration.
The James Webb Space Telescope (JWST) observations have been demonstrated to be efficient in detecting globular clusters' (GCs) multiple stellar populations in the low mass regime of M dwarfs. We ...present an overview, and first results, of different projects that can be explored by using the JWST observations gathered under the GO2560 for 47 Tucanae, a first program entirely devoted to the investigation of multiple populations in very low mass stars, which includes spectroscopic data for the faintest GC stars for which spectra are available. Our color-magnitude diagram (CMD) shows some substructures for ultracool stars, including gaps and breaks in slope. In particular, we observe both a gap and a minimum in the F322W2 luminosity function less than one magnitude apart, and discuss which one could be associated with the H-burning limit. We detect stars fainter than this minimum, very likely the brown dwarfs. We corroborate the ubiquity of the multiple populations across different masses, from ~0.1 solar masses up to red giants (~0.8 solar masses). The oxygen range inferred from the M dwarfs, both from the CMD and from the spectra of two M dwarfs associated with different populations, is similar to that observed in giants. We have not detected any difference between the fractions of stars in distinct populations across stellar masses >~0.1 solar masses. This work demonstrates the JWST's capability in uncovering multiple populations within M dwarfs and illustrates the possibility to analyse very low-mass stars in GCs approaching the H-burning limit and the brown-dwarf sequence.
BACKGROUND AND AIMS: Accelerated berry sugar accumulation resulting in wines of excessive alcohol concentration, subâoptimal colour and atypical flavour has become increasingly frequent in warm ...growing districts, a trend induced by factors that include global warming. The application of a filmâforming antitranspirant may be an effective way of reducing early sugar accumulation without affecting colour development. METHODS AND RESULTS: An antitranspirant emulsion was applied in 2013 and in 2014 on fieldâgrown cv. Barbera vines at preâflowering (PF), preâveraison (PV) and at both dates (PFPV), and compared with the unsprayed control. Postâtreatment assessment included seasonal gas exchange, yield components, growth of berry organs and must composition. Although all treatments were effective in reducing gas exchange by as much as 46% compared with that of the control, berry growth was not affected. Conversely, whereas PF slightly modified the ripening pattern, PV and PFPV markedly delayed accumulation of sugar in the warm 2013 season (â2.4 and â3.7° Brix, respectively, vs control) without detriment to colour development because the onset of anthocyanins occurred at lower TSS. In the cooler, wet 2014 season, PV and PFPV were again able to delay sugar accumulation without affecting colour development. CONCLUSIONS: Preâveraison application of the antitranspirant alone or in combination with a PF spray proved effective in slowing sugar accumulation while avoiding concurrent delay of colour development. SIGNIFICANCE OF THE STUDY: The use of antitranspirants is a practical and flexible way of regulating the sugarâ:âanthocyanin ratio under conditions of excessively fast ripening.
Background and Aims
Global warming is inducing a general earliness in the onset of grapevine phenological stages including ripening, a phenomenon that occurs often in the hottest seasons and which ...leads to unbalanced wines. Our aim was to assess the physiological basis of late leaf removal applied above the bunch area as a tool for delaying ripening.
Methods and Results
Potted cv. Sangiovese grapevines were subjected to leaf removal treatments applied preveraison (DEF‐I) and postveraison (DEF‐II) by pulling out six to seven primary leaves and laterals, if any, above the bunch zone; untouched vines served as the control. Whole‐canopy net CO2 gas exchange was monitored seasonally from 9 days before DEF‐I to 35 days after DEF‐II. Concurrently, single‐leaf gas exchange was assessed, and at harvest yield components, grape composition and the leaf‐to‐fruit ratio were determined. The seasonal carbon/yield ratio did not differ between treatments because of the high capacity for photosynthetic compensation shown by the DEF treatments and quantified as about a 35% higher net CO2 gas exchange per unit of leaf area per day. While ripening was temporarily retarded in both DEF treatments, with sugar content being lower and titratable acidity higher, a week later both treatments had fully or partially recovered; phenolic ripening was unaffected at either harvest date.
Conclusions
Defoliation above the bunch zone applied at lag‐phase and postveraison (average 12°Brix) was effective in temporarily delaying technological ripeness without affecting colour and phenolics. This result depended upon the high compensation capacity for photosynthesis shown by vines in both treatments.
Significance of the Study
The data provide a preliminary yet robust physiological background for targeting better field application of the technique.
Testing of new rootstocks for drought tolerance targets traditionally rain-fed districts where supplemental irrigation is more frequently needed due to the pressures of global warming. A seasonal ...evaluation of gas exchange and water-use efficiency (WUE) of cv. Sangiovese grafted to the new drought-tolerant genotype M4 in a dry-down trial against the commercial SO4 stock is reported. The experiment was conducted in 2014 on twelve 2-year-old, non-fruiting potted Sangiovese grapevines grafted on M4 and SO4 stocks and assigned to SO4-WW (well-watered), SO4-WS (water-stressed), M4-WW and M4-WS treatments. Progressive water deficit was imposed by reducing water supply to 70, 50 and 30 % of whole-canopy demand derived from concurrent measurements of transpiration in WW. Unlike SO4, M4 showed slower stress progression, as highlighted by pre-dawn leaf water potential, and retained higher whole-canopy net CO
2
exchange rates (NCER) and transpiration rates per unit of leaf area at all replenishment levels as well as exhibiting higher canopy WUE at both 50 and 30 % WW. Although single-leaf assessment was in partial disagreement with data recorded on the whole-canopy basis, robust data were acquired to confirm that the M4 stock performs better than SO4 at any water replenishment level in terms of higher NCER/leaf area and/or canopy WUE. Findings feed expectations that grafting Sangiovese to the M4 rootstock should result in a problem-solving tool for rain-fed areas subject to temporary summer drought.
Background and Aims: While shoot thinning is one of the most widely applied practices in the vineyard as a tool to regulate canopy density and/or crop level, its physiological bases are still fairly ...obscure and have been poorly investigated. Our aim was to assess seasonal modification of whole‐canopy net CO2 exchange rate (NCER) in thinned and non‐thinned grapevines, as well as establishing correlations with grape composition.
Methods and Results: Potted, mature cv. Barbera vines were thinned (ST) to 10–15 shoots/m over the two trial years and compared with a non‐thinned control (C). The data logged each season included whole‐vine NCER monitored pre‐ and post‐veraison for periods of variable lengths, vine growth, yield components and grape composition. While final leaf area per vine did not differ between treatments, ST showed reduced yield and improved berry colour and must sugar accumulation. In 2009, NCER/vine recovery in ST was 85% of C at verasion, whereas in 2010 full recovery was already reached around bloom.
Conclusions: A load of 15 shoots/m maximised canopy efficiency by inducing the fastest recovery of whole‐vine photosynthesis and markedly improved sugar, colour and phenolics. Retaining 10 shoots/m delayed NCER recovery while improving overall grape composition as compared to C.
Significance of the Study: Direct assessment of the complex seasonal canopy NCER dynamics triggered by shoot thinning indicates that the source‐sink balance evolves in ST towards a higher supply of assimilates per unit of crop than that available in non‐thinned canopies during the veraison‐to‐harvest period.
