Alan Davison - Academia.edu (original) (raw)
Papers by Alan Davison
The Bryologist, 1993
ABSTRACT Specimens of six lichen species (Evernia prunastri (L.) Ach., Hypogymnia physodes (L.) N... more ABSTRACT Specimens of six lichen species (Evernia prunastri (L.) Ach., Hypogymnia physodes (L.) Nyl., Parmelia saxatilis (L.) Ach., Platismatia glauca (L.) W. Culb. & C Culb., Pseudevernia furfuracea (L.) Zopf., and Ramalina farinacea (L.) Ach.) were maintained at 5 mumol photons m-2 sec.-1 for 2 days. Then the fluorescence parameters F(o), F(p), F(v), and F(v)/F(m) were measured. Photoinhibition way studied at 300 and 1,000 mumol photons m-2 sec.-1 of light irradiance for 3 days, and then al 20 mumol photons m-2 sec.-1 for 5 hr. to achieve recovery. Different patterns of photoinhibition were observed among the considered species. Hypogymnia physodes, P. glauca, and P. furfuracea exhibited a significant decline in the F(v)/F(p) ratio (indicative of photoinhibition) at both photon flux densities. Platismatia glauca and P. furfuracea presented a significant increase of F(o) (photoinhibitory damage to Photosystem II centers). Furthermore, P. glauca was not able to recover after a period of lower photon flux density (PFD). In contrast, E. prunastri, P. saxatilis, and R. farinacea were only photoinhibited when exposed to the highest PFD, and always recovered. With the exception of P. saxatilis, there is a close correspondence between the species' sensitivity to the light treatments and their water relations, measured in terms of wet event duration, rate of water loss, and maximum thallus water content. A possible role of the previous light history at their natural habitats is also discussed.
New Phytologist, 1997
The relative ozone resistance of 20 European and two American populations oi Plantago major was e... more The relative ozone resistance of 20 European and two American populations oi Plantago major was examined, and relationships with climatic factors at the source of the plant material were explored using data provided by participants in the ICP-Crops initiative (International Co-operative Programme to Investigate the Effects of Air Pollutants and Other Stresses on Agricultural and Semi-Natural Vegetation). Plants grown from seed were exposed to either charcoal/Purafil® filtered air (CF < 5 nmol mol"^ O3) or CF 4-ozone (70 nmol mol"^ O3 7 h d~^) over a 2-wk period in controlled environment chambers, and effects on mean plant relative growth rate (R) and allometric root/shoot growth (K) determined. Ozone resistance (R%) was calculated from (Ro^/R^,^) x 100.
New Phytologist, 1998
Although there is a great deal of concern about the effects of human activities on biodiversity, ... more Although there is a great deal of concern about the effects of human activities on biodiversity, until recently there has been very little interest in the effects of ozone on the species that constitute the major part of the flora, the diverse herbaceous and shrubby species of natural and semi-natural communities. However, many wild species have been shown to be at least as sensitive to ozone as crops that show significant yield losses, so there is a pressing need for an evaluation of the risk to wild species posed by ozone. This review attempts to assess progress and highlight problems. It begins with a comment on semantics, discusses the difficulties involved in measuring relative ozone resistance and then proceeds to consider the effects of ozone on growth and resource allocation. The evidence for evolution of resistance is appraised and then the potential effects of several interactions (cutting\grazing, competition, soil water deficit and nutrition) are considered. The review ends with some remarks on observation of oxidant-induced changes in ecosystems. Ashmore MR, Ainsworth N. 1995. The effects of cutting on the species composition of artificial grassland communities.
Environmental and Experimental Botany, 1992
New Phytologist, 1998
Although there is a great deal of concern about the effects of human activities on biodiversity, ... more Although there is a great deal of concern about the effects of human activities on biodiversity, until recently there has been very little interest in the effects of ozone on the species that constitute the major part of the flora, the diverse herbaceous and shrubby species of natural and semi-natural communities. However, many wild species have been shown to be at least as sensitive to ozone as crops that show significant yield losses, so there is a pressing need for an evaluation of the risk to wild species posed by ozone. This review attempts to assess progress and highlight problems. It begins with a comment on semantics, discusses the difficulties involved in measuring relative ozone resistance and then proceeds to consider the effects of ozone on growth and resource allocation. The evidence for evolution of resistance is appraised and then the potential effects of several interactions (cutting\grazing, competition, soil water deficit and nutrition) are considered. The review ends with some remarks on observation of oxidant-induced changes in ecosystems. Ashmore MR, Ainsworth N. 1995. The effects of cutting on the species composition of artificial grassland communities.
The Bryologist, 1993
ABSTRACT Specimens of six lichen species (Evernia prunastri (L.) Ach., Hypogymnia physodes (L.) N... more ABSTRACT Specimens of six lichen species (Evernia prunastri (L.) Ach., Hypogymnia physodes (L.) Nyl., Parmelia saxatilis (L.) Ach., Platismatia glauca (L.) W. Culb. & C Culb., Pseudevernia furfuracea (L.) Zopf., and Ramalina farinacea (L.) Ach.) were maintained at 5 mumol photons m-2 sec.-1 for 2 days. Then the fluorescence parameters F(o), F(p), F(v), and F(v)/F(m) were measured. Photoinhibition way studied at 300 and 1,000 mumol photons m-2 sec.-1 of light irradiance for 3 days, and then al 20 mumol photons m-2 sec.-1 for 5 hr. to achieve recovery. Different patterns of photoinhibition were observed among the considered species. Hypogymnia physodes, P. glauca, and P. furfuracea exhibited a significant decline in the F(v)/F(p) ratio (indicative of photoinhibition) at both photon flux densities. Platismatia glauca and P. furfuracea presented a significant increase of F(o) (photoinhibitory damage to Photosystem II centers). Furthermore, P. glauca was not able to recover after a period of lower photon flux density (PFD). In contrast, E. prunastri, P. saxatilis, and R. farinacea were only photoinhibited when exposed to the highest PFD, and always recovered. With the exception of P. saxatilis, there is a close correspondence between the species' sensitivity to the light treatments and their water relations, measured in terms of wet event duration, rate of water loss, and maximum thallus water content. A possible role of the previous light history at their natural habitats is also discussed.
New Phytologist, 1997
The relative ozone resistance of 20 European and two American populations oi Plantago major was e... more The relative ozone resistance of 20 European and two American populations oi Plantago major was examined, and relationships with climatic factors at the source of the plant material were explored using data provided by participants in the ICP-Crops initiative (International Co-operative Programme to Investigate the Effects of Air Pollutants and Other Stresses on Agricultural and Semi-Natural Vegetation). Plants grown from seed were exposed to either charcoal/Purafil® filtered air (CF < 5 nmol mol"^ O3) or CF 4-ozone (70 nmol mol"^ O3 7 h d~^) over a 2-wk period in controlled environment chambers, and effects on mean plant relative growth rate (R) and allometric root/shoot growth (K) determined. Ozone resistance (R%) was calculated from (Ro^/R^,^) x 100.
New Phytologist, 1998
Although there is a great deal of concern about the effects of human activities on biodiversity, ... more Although there is a great deal of concern about the effects of human activities on biodiversity, until recently there has been very little interest in the effects of ozone on the species that constitute the major part of the flora, the diverse herbaceous and shrubby species of natural and semi-natural communities. However, many wild species have been shown to be at least as sensitive to ozone as crops that show significant yield losses, so there is a pressing need for an evaluation of the risk to wild species posed by ozone. This review attempts to assess progress and highlight problems. It begins with a comment on semantics, discusses the difficulties involved in measuring relative ozone resistance and then proceeds to consider the effects of ozone on growth and resource allocation. The evidence for evolution of resistance is appraised and then the potential effects of several interactions (cutting\grazing, competition, soil water deficit and nutrition) are considered. The review ends with some remarks on observation of oxidant-induced changes in ecosystems. Ashmore MR, Ainsworth N. 1995. The effects of cutting on the species composition of artificial grassland communities.
Environmental and Experimental Botany, 1992
New Phytologist, 1998
Although there is a great deal of concern about the effects of human activities on biodiversity, ... more Although there is a great deal of concern about the effects of human activities on biodiversity, until recently there has been very little interest in the effects of ozone on the species that constitute the major part of the flora, the diverse herbaceous and shrubby species of natural and semi-natural communities. However, many wild species have been shown to be at least as sensitive to ozone as crops that show significant yield losses, so there is a pressing need for an evaluation of the risk to wild species posed by ozone. This review attempts to assess progress and highlight problems. It begins with a comment on semantics, discusses the difficulties involved in measuring relative ozone resistance and then proceeds to consider the effects of ozone on growth and resource allocation. The evidence for evolution of resistance is appraised and then the potential effects of several interactions (cutting\grazing, competition, soil water deficit and nutrition) are considered. The review ends with some remarks on observation of oxidant-induced changes in ecosystems. Ashmore MR, Ainsworth N. 1995. The effects of cutting on the species composition of artificial grassland communities.