Studies ON THE TOLERANCE TO SULPHUR DIOXIDE OF GRASS POPULATIONS IN POLLUTED AREAS

Abstract

SUMMARYDactylis glomerata, Festuca rubra, Holcus lanatus, Lolium perenne and Phleum bertolonii were collected from one or more of three sites with differing pollution characteristics in the north of England, and screened for tolerance to both acute and chronic sulphur dioxide injury in comparison with either bred cultivars or individuals of the same species collected from clean areas. Selection for tolerance was detected in all species and at all sites, suggesting that tbis is widespread in the field.Differential response to chronic injury was manifested as effects on senescence, dry matter production, and/or partition of assimilate between roots and shoots. No correlation was found between the degree of acute and chronic injury at either the intraspecific or interspecific levels, which may indicate independent physiological mechanisms for these. Tolerance may evolve within 17 to 25 years. The significance of the evolution of SOg tolerance for grasslands at polluted sites is discussed.

RELATIVE PERFORMANCE OF CONIFER POPULATIONS IN VARIOUS TESTS FOR SENSTIVITY TO SO2, AND THE IMPLICATIONS FOR SELECTING TREES FOR PLANTING IN POLLUTED AREAS

“…This study has demonstrated that the absence of a relationship between the effects of acute and chronic exposures to SOg described for grasses by Horsman et al (1979) and Ayazloo and Bell (1981) also occurs in trees. The order of sensitivity of the populations to SOg depended primarily on the concentration and duration of exposure, and it was evident that short exposures to high concentrations are of little use for selecting tree genotypes likely to be resistant at field sites where only chronic injury is expected.…”

“…The need for this approach was first shown by Horsman et al (1979) who found that in a single population of Lolium perenne there was no relationship between the relative sensitivities of individual genotypes to acute and chronic injury. In a simultaneous but more detailed study, involving 20 populations from five grass species, Ayazloo and Bell (1981) found a lack of correlation between sensitivity to acute and chronic injury in every population.…”

Studies ON THE TOLERANCE TO SULPHUR DIOXIDE OF GRASS POPULATIONS IN POLLUTED AREAS

“…Bradshaw (1977) uses it to describe the overall ability to withstand an environmental stress, while for Levitt (1972) it implies that the mechanism is internal (physiological) rather than one of avoidance, and the term 'resistance' is used to define the overall mechanism. Ayazloo and Bell (1981) used ' tolerance' in the same context as Bradshaw and this is continued in the present paper. To imply an internal mechanism of withstanding stress ('tolerance' in the sense of Levitt), we use the term 'physiological tolerance'.…”

“…In the previous paper (Ayazloo and Bell, 1981), it was shown that populations of grasses from areas with a history of sulphur dioxide (SOg) pollution have a greater degree of tolerance to SOg than populations from unpolluted sites or bred cultivars. It was demonstrated that tolerance of acute injury occurred independently of tolerance of long term chronic injury caused by lower levels of SOg.…”

“…Thus it is improbable that tolerance can be explained by a single overall mechanism. In the present paper some possible mechanisms of tolerance to both types of injury are examined in the populations of grasses used by Ayazloo and Bell (1981).…”