Stephan Flint - Academia.edu (original) (raw)

Papers by Stephan Flint

Photochemical & Photobiological Sciences, 2019

Physiologia Plantarum, Apr 1, 1995

Broad-band UV-B radiation inhibited hypocotyl elongation in etiolated tomato iLxcapersicon e.scii... more Broad-band UV-B radiation inhibited hypocotyl elongation in etiolated tomato iLxcapersicon e.sciilentiim Mill, cv, Alisa Craig) seedlings. This inhibition could be elicited by < 3 nmol ny-s' of UV-B radiation provided against a background of white light l> 620 pmol m"" s"' between 320 and 800 nm), and was similar in wild-type and phytochrome-l-deficient aiirea mutant seedlings. These observations suggest that the effect of UV-B radiation is not mediated by phytochrome. An activity spectrum obtained hy delivering I fimol m"" s" of monochromatic UV radiation against a white light background (63 pmol nr-s"') showed maximum effectiveness around 3(X) nm. which suggests that DN.A or aromatic residues in proteins arc not the chromophores mediating UV-B induced inhibition of elongation. Chemicals that affect tbe normal (photo)chemislry of flavins and possihiy pterins (Kl. NaN^ and phenylacetic acid) largely abolished the inhibitory effect of broad-hand UV-B radiation when applied to the root zone hefore irradiation. KI was effective at concentrations < lO-* M. which have been shown in vitro to he effective in quenching the triplet excited states of flavins hut not fluorescence from pterine or singlet states of flavins. Elimination of blue light or reduction of UV-A, two sources of llavin excitation, promoted hypocoty] elongation, but did not affect tbe inhibition of elongation exerted by UV-B. Kl applied after UV-B irradiation had no effect on the inhihition response. Taken together these findings suggest that the chromophore of tbe photoreceptor system invohed in UV-B perception by tomato seedlings during de-etiolation may be a flavin.

Oecologia, Mar 1, 1990

A multispecies canopy photosynthesis simulation model was used to examine the importance of canop... more A multispecies canopy photosynthesis simulation model was used to examine the importance of canopy structure in influencing light interception and carbon gain in mixed and pure stands of wheat (Triticum aestivum L.) and wild oat (Arena fatua L.), a common weedy competitor of wheat. In the mixtures, the fraction of the simulated canopy photosynthesis contributed by wheat was found to decline during the growing season and this decline was closely related to reductions in the amount of leaf area in upper canopy layers. For both species in mixture and in monoculture, simulated photosynthesis was greatest in the middle or upper-middle canopy layers and sensitivity analyses revealed that canopy photosynthesis was most sensitive to changes in leaf area and leaf inclination in these layers. Changes in LAI and leaf inclination affected canopy carbon gain differently for mixtures and monocultures, but the responses were not the same for the two species. Results from simulations where the structural characteristics of the two species were substituted indicated that species differences in leaf inclination, sheath area and the fraction of leaf area alive were of minor consequence compared with the differences in total leaf area in influencing relative canopy carbon gain in mixtures. Competition for light in these species mixtures appears to be influenced most by differences in the positioning of leaf area in upper canopy layers which determines, to a great extent, the amount of light intercepted.

Springer eBooks, 1986

... Page 15. 101 Biological Assessments and Errors Deriving from Action Spectra Before radiation ... more ... Page 15. 101 Biological Assessments and Errors Deriving from Action Spectra Before radiation amplification factors can be used in assessment of biolog-ical and ecological consequences of ozone reduction, it is necessary to demonstrate biological effects of UV-R radiation. ...

Physiologia Plantarum, Apr 28, 2021

The ecological and photobiological communities lost a leader, a pioneer, and a beloved mentor rec... more The ecological and photobiological communities lost a leader, a pioneer, and a beloved mentor recently with the death of Martyn M. Caldwell, who passed away January 24, 2021, in Washington, DC, after an extended battle with Parkinson's and Lewy body disease. While Martyn was instrumental in the development of the field of ultraviolet (UV) environmental photobiology, he was foremost a renowned plant physiological ecologist who played a leading role in the advancement of this discipline throughout the world. After receiving his Ph.D. from Duke University, where he studied with W. Dwight Billings, Martyn spent his academic career (41 years

Annals of Botany, Nov 1, 1977

American Biology Teacher, Oct 1, 1985

The promotion or inhibition of seed germination by light is a dramatic effect of environment on d... more The promotion or inhibition of seed germination by light is a dramatic effect of environment on development. For the past 25 years it has been known that the protein phytochrome mediates this, as well as several other plant developmental responses to light. Phytochrome exists in two forms, which are interconverted by absorption of light of appropriate wavelengths. The red-absorbing form (Pr) is converted into the far-red-absorbing form (Pfr) by wavelengths between about 550-700 nm. Pfr is converted to Pr by wavelengths between about 700-800 nm, known as far-red light. The ratio of Pr/Pfr in a plant tissue influences development. For an introduction to the physiology and ecology of these phenomena, consult chapter 19 in Salisbury and Ross (1978).

OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Dec 31, 1994

This essay will consider both physical and photobiological aspects of controlled environment ligh... more This essay will consider both physical and photobiological aspects of controlled environment lighting in the spectral region beginning in the blue and taken to the normal limit of the solar spectrum in the ultraviolet. The primary emphasis is directed to questions of plant response to sunlight. Measurement and computations used in radiation dosimetry in this part of the spectrum are also briefly treated.

ASSA, CSSA and SSSA, Nov 2, 2015

I As originally defined (Coblentz, 1932), the UV spectrum is: UV-A, 315 to 400 nm; UV-B, 280 to 3... more I As originally defined (Coblentz, 1932), the UV spectrum is: UV-A, 315 to 400 nm; UV-B, 280 to 315 nm; and UV-C, <280 nm. However, the division between UV-A and UV-B is often taken as 320 nm.

The ultraviolet action spectrum for photosynthesis inhibition was determined to fall between that... more The ultraviolet action spectrum for photosynthesis inhibition was determined to fall between that of the general DNA action spectrum and the generalized plant action spectrum. The characteristics of this action spectrum suggest that a combination of pronounced increase in effectiveness with decreasing wavelength, substantial specificity for the UV-B waveband, and very diminished response in the UV-A waveband result in large radiation amplification factors when the action spectra are used as weighting functions. Attempted determination of dose/response relationships for leaf disc inhibition provided inconclusive data from which to deconvolute an action spectrum.

Nature Sustainability, 2019

Thirty-three years ago, an unprecedented thinning of stratospheric ozone was reported over Antarc... more Thirty-three years ago, an unprecedented thinning of stratospheric ozone was reported over Antarctica 1. In response to concerns about elevated exposure to solar ultraviolet-B radiation (UV-B; wavelengths 280-315 nm) resulting from ozone depletion, the international community mobilized and worked together to understand the causes and find a solution to this dramatic change in Earth's environment. The policy solution that emerged to address this global environmental problem was the 1985 Vienna Convention for the Protection of the Ozone Layer. In this international agreement the United Nations recognized the fundamental importance of preventing the damaging effects of stratospheric ozone depletion, whether on human health or the environment. This convention was followed by the 1987 Montreal Protocol on Substances that Deplete the Ozone Layer with its subsequent amendments, adjustments, and decisions that were negotiated to control the consumption and production of anthropogenic ozone-depleting substances, including chlorofluorocarbons (CFCs). The Montreal Protocol now has the unique distinction of being the only treaty, ever, of any type, ratified by all 197 countries of the United Nations. The Parties to the Montreal Protocol base their decisions on scientific, environmental, technical, and economic information provided by three assessment Panels (Box 1). All three panels provide full assessment reports to the Parties every four years (quadrennial reports) and shorter, periodic updates in the intervening years as needed. The implementation of the Montreal Protocol has successfully prevented the uncontrolled global depletion of the stratospheric ozone layer 2,3. Concentrations of ozonedepleting substances have been declining in the stratosphere since the late 1990s. While significant seasonal ozone depletion over Antarctica has occurred annually since the 1980s (called the "ozone hole"), there have been small, but significant, positive trends in total column ozone in Antarctica in spring over the period 2001-2013. Global mean total ozone has been projected to recover to pre-1980 levels by about the middle of the 21 st century, assuming full compliance to the Montreal Protocol 2. Many of the chemical compounds controlled by the Montreal Protocol are not only involved in depletion of stratospheric ozone, but are also potent greenhouse gases 4. Modeling studies indicate that, in the absence of the Montreal Protocol, global mean temperatures would have risen by more than 2C by 2070, due to the warming effects from ozone-depleting substances alone 5. The adoption of the Kigali Amendment to the Montreal Protocol in 2016 limits the production and consumption of hydrofluorocarbons (HFCs), powerful greenhouse gases that are used as substitutes to ozone-depleting substances. This amendment has further broadened and strengthened the scope of the Montreal Protocol, creating an effective international treaty that not only addresses stratospheric ozone depletion, but is doing more to mitigate global climate change than any other human actions to date 7-10. One of the important reasons for the success of the Montreal Protocol has been its foundation on high quality science, which not only improves our understanding of the causes and mechanisms of ozone depletion, but also of the environmental effects of these atmospheric changes. The Environmental Effects Assessment Panel (EEAP) is specifically charged with providing regular assessments of the state of the science on the environmental effects of ozone depletion and consequent changes in UV radiation at Earth's surface, and the interactive effects of climate change (Box 1 and Fig. 1). Here, we summarize key findings from the most recent EEAP Quadrennial Assessment, and consider the significant policy and societal implications of these environmental effects. We specifically highlight the multiple ways by which the Montreal Protocol is contributing to environmental sustainability and human health and well-being consistent with many of the United Nations Sustainability Goals (Box 2). More in-depth information on ozone depletion and its environmental effects can be found in the full Assessments published by the Ozone Secretariat of the United Nations Environment Programme (https://ozone.unep.org) and elsewhere (Photochemical & Photobiological Sciences journal) 11-17. By focusing on the interactions between stratospheric ozone dynamics, UV radiation, and climate change, the report from the EEAP complements that of the UN's Intergovernmental Panel on Climate Change (IPCC;https://www.ipcc.ch; summarized by Pachauri, et al. 18) to provide a comprehensive assessment on the environmental effects of global changes in Earth's atmosphere.

Arctic and Alpine Research, 1987

Page 1. Arctic and Alpine Research, Vol. 19, No. 1, 1987, pp. 21-27 PHOTOSYNTHESIS DAMAGE AND PRO... more Page 1. Arctic and Alpine Research, Vol. 19, No. 1, 1987, pp. 21-27 PHOTOSYNTHESIS DAMAGE AND PROTECTIVE PIGMENTS IN PLANTS FROM A LA1l11UDINAL ARCTIC/ALPINE GRADIENT EXPOSED TO SUPPLEMENTAL UV-B RADIATION IN THE FIELD ...

Functional Ecology, 1988

... PW BARNES*, PW JORDANt, WG GOLDt, SD FLINT and MM CALDWELL Department of Range Science and Ec... more ... PW BARNES*, PW JORDANt, WG GOLDt, SD FLINT and MM CALDWELL Department of Range Science and Ecology Center, Utah State University ... experi-ment were similar, differential effects of UV-B on species growth form: leaf insertion heights and leaf blade lengths were ...

Photochemical & Photobiological Sciences

Linkages between stratospheric ozone, UV radiation and climate change: terrestrial ecosystems.

Frontiers in Plant Science

Journal of Photochemistry and Photobiology B Biology, Jun 10, 2009