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Dose–response of germinating Rudbeckia mollis (Asteraceae) seeds exposed to various thermal scenarios
- Keith Kettner, Hector Eduardo Pérez
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- Journal:
- Seed Science Research / Volume 22 / Issue 3 / September 2012
- Published online by Cambridge University Press:
- 08 June 2012, pp. 191-197
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Temperature is a key environmental signal regulating germination. A thorough understanding of how seed populations respond to various temperatures can inform end-users regarding effective establishment strategies and forms the basis for questions related to a taxon's thermo-biology. Although abundant information exists regarding germination responses of economically important crops to several temperature scenarios, much less is known concerning the seed biology of wild germplasm. To address this, we examined the germination response of non-dormant Rudbeckia mollis seeds to various doses of constant or simulated seasonal diel temperatures. Germination response was sigmoidal. Seeds of R. mollis were capable of germinating within a few days to high percentages (>95%) at relatively cool constant (15–25°C) or 12-hour alternating (22/11–33/24°C) temperatures, with optimum temperatures for germination occurring at 25°C or 29/19°C. Germination was inhibited as temperatures increased to 30°C or 33/24°C with early and late germinating phenotypes displaying differential responses at these temperatures. No germination occurred at 35°C. Results are discussed in terms of seedling establishment of R. mollis outside its natural range and implications of climate change on germination.
The Giant HII Region NGC 2363
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- By Rosa González-Delgado, Instituto de Astrofísica de Canarias, E-38200 La Laguna, Tenerife, Spain, Enrique Pérez, Instituto de Astrofísica de Canarias, E-38200 La Laguna, Tenerife, Spain, Guillermo Tenorio-Tagle, Instituto de Astrofísica de Canarias, E-38200 La Laguna, Tenerife, Spain, José M. Víchez, Instituto de Astrofísica de Canarias, E-38200 La Laguna, Tenerife, Spain, Elena Terlevich, Royal Greenwich Observatory, Madingley Road, Cambridge CB3 0EZ, UK, Roberto J. Terlevich, Royal Greenwich Observatory, Madingley Road, Cambridge CB3 0EZ, UK, Eduardo Telles, Royal Greenwich Observatory, Madingley Road, Cambridge CB3 0EZ, UK, José M. Rodríguez-Espinosa, Instituto de Astrofísica de Canarias, E-38200 La Laguna, Tenerife, Spain, Miguel Mas-Hesse, Laboratorio de Astrofísica Espacial y Física Fundamental (LAEFF), Apdo. 50727, 28080 Madrid, Spain, María Luisa García-Vargas, Depto. Física Teórica CIX, Universidad Autónoma, Cantoblanco, 28049 Madrid, Spain, Ángeles I. Díaz, Depto. Física Teórica CIX, Universidad Autónoma, Cantoblanco, 28049 Madrid, Spain, Jordi Cepa, Instituto de Astrofísica de Canarias, E-38200 La Laguna, Tenerife, Spain, Hector Castañeda, Instituto de Astrofísica de Canarias, E-38200 La Laguna, Tenerife, Spain
- G. Tenorio-Tagle, Instituto de Astrofísica de Canarias, Tenerife
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- Book:
- Violent Star Formation
- Published online:
- 10 November 2010
- Print publication:
- 22 September 1994, pp 117-122
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Summary
We present narrow-band Hα imaging and long-slit optical and near infrared spectroscopy of the giant HII region NGC 2363. We have found broad emission lines at 4686 Å and at 5810 Å attributed to WC stars at 6 arcsec to the East of the brightest core of the region. We confirm the existence of low-intensity broad components in Hα and [OIII] which extend some 500 pc. We have derived the physical conditions and chemical composition of the gas in 15 different zones in the region, and do not find significant variations in the abundances. The Paschen discontinuity has been found in emission. The Pa electron temperatures obtained are significantly smaller than those obtained from the [OIII] and [SIII] emission lines, indicating the presence of large temperature fluctuations.
Introduction
One of the targets of the GEFE programme is the giant HII region NGC 2363 located in the SW of the irregular galaxy NGC 2366. This is one of the largest extragalactic HII regions with high surface brightness. The object was observed in La Palma in narrow band Hα and long-slit spectrophotometry from [OII] λ3227 to [SIII] λ9532 at two positions, at the brighest core of the region (which we call knot A) and at 6 arcsec to the East (knot B).
Narrow-band images
The object was observed with the 1-m JKT telescope. We used a CCD with a spatial scale of 0.3 arcsec pixel−1.