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The response of native, herbaceous species to ozone: growth and fluorescence screening
Author(s) -
REILING K.,
DAVISON A. W.
Publication year - 1992
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1992.tb01055.x
Subject(s) - herbaceous plant , plantago , biology , population , shoot , allometry , taxon , chlorophyll fluorescence , botany , ecology , chlorophyll , demography , sociology
summary Ozone concentrations in many parts of Europe exceed the proposed UN‐ECE Critical Levels for the protection of ecosystems but there is so little known about the effects on native, herbaceous species, that it is presently impossible to judge what effect, if any, these concentrations are having on this group of plants. This paper reports the results of an initial screening of 32 taxa that was used to select a small number of species for further work. All were exposed to 70 nl 1 −1 O 3 given for 7 h d −1 for two weeks and the response measured in terms of mean relative growth rate (R̄), the allometric root/shoot coefficient (K), and changes in induced chlorophyll fluorescence (F R ). Only six species showed visible symptoms but 14 showed a significant reduction in R̄. There was no relationship between the extent of visible symptoms and growth reduction, confirming that visible symptoms are often of little value in determining growth sensitivity to O 3 stress. There were marked differences within genera and within species; a population of Plantago major collected in Athens showed no effects, while a Derbyshire population, with a 24% reduction in R̄, was the most sensitive of taxa tested, including Bel‐W3 tobacco which has been specifically bred for O 3 sensitivity. There was a significant regression of R % change on the R̄ of controls (R̄%= 12.4−10.4 ×R̄, P= 0.0007, r =−0.56), implying that > 30% of the variation in response between taxa was related to the inherent R̄; faster growing taxa tending to show a greater reduction in R̄ on exposure to O 3 . It is tentatively suggested that this may be related to differences in stomatal conductance. Ozone caused a significant shift in K in 14 taxa, with many of the biggest changes being in grasses. Although O 3 reduced K in some taxa, contrary to several published accounts, it increased it in others, and in some there was an effect on K with no effect on R̄. Possible reasons for this are discussed. Chlorophyll fluorescence was examined as a tool for detecting O 3 stress. The maximum rate of rise of induced fluorescence, F R , was very sensitive to O 3 but showed a complex pattern of response dependent on species and time. Most taxa showed a significant change in F R , even when there was no effect of the O 3 on R̄ or K. Whilst the sensitivity of F R makes it a useful method for in vivo detection of O 3 stress, the complexity of the response makes it very difficult to quantify and use for comparisons between species.