Influence of plant age on ozone resistance in Plantago major

Abstract

$ on growth and reproductive performance confirmed the sensitivity of the population to the pollutant. In the absence of the development of typical visible symptoms of foliar damage, the total d. wt of plants maintained in O $ over a 56-d period was 35 % lower than that of control plants. However, the impact of the pollutant was found to decrease as plants aged. Plant relative growth rate (R E ) was only affected in seedlings, suggesting that effects of O $ on seedling growth were largely responsible for the decrease in accumulated biomass ; the growth rate of older plants was not affected by O $ . The observed shift in O $ resistance with plant age was mediated by both ' acclimation ' and ontogenetic changes. ' Acclimation ' was not associated with changes in O $ uptake, and there was some evidence to support the existence of compensatory growth responses. In addition to effects on vegetative growth, plants exhibited an O $ -induced decline in reproductive performance ; O $ reducing the number of flower spikes and seed capsules produced per plant. Ozone episodes administered at different stages of development indicated that reproductive development was particularly sensitive to O $ during the early stages of flowering.The findings of this study are discussed in relation to evolutionary adaptation to O $ in natural plant communities.The importance of plant age, prior exposure to the pollutant and the timing of O $ episodes in relation to plant developmental stage are highlighted.

Impacts of ozone on Plantago major: apoplastic and symplastic antioxidant status

“…Considerable variation in O $ resistance exists both within and between plant species (Davison & Barnes, 1998 ;Barnes et al, 1998). Furthermore, resistance is affected by the timing of the O $ exposure in relation to the stage of plant development (Reinert & Henderson, 1980 ;Walmsley et al, 1980 ;Krupa & Manning, 1988 ;Held et al, 1991 ;Kasana, 1991 ;Conklin et al, 1996) and is influenced by numerous environmental factors (Wolfenden & Mansfield, 1991 ;Polle & Rennenberg, 1993 ;Barnes & Wellburn, 1998).…”

“…Furthermore, resistance is affected by the timing of the O $ exposure in relation to the stage of plant development (Reinert & Henderson, 1980 ;Walmsley et al, 1980 ;Krupa & Manning, 1988 ;Held et al, 1991 ;Kasana, 1991 ;Conklin et al, 1996) and is influenced by numerous environmental factors (Wolfenden & Mansfield, 1991 ;Polle & Rennenberg, 1993 ;Barnes & Wellburn, 1998). Previous work on Plantago major has demonstrated that the adverse effects of O $ on growth decrease with plant age (Reiling & Davison, 1992 ;Lyons & Barnes, 1998 ;Zheng, 1998). The objective of the present study was to examine whether shifts in antioxidant status accompany previously reported age-related shifts in O $ resistance (Lyons & Barnes, 1998), paying special attention to the potential scavenging of ROS in the apoplast.…”

“…Effects on wild species are more difficult to quantify. However, the pollutant is known to be responsible for subtle shifts in the genetic composition of native plant communities (Fuhrer et al, 1997 ;Barnes et al, 1998 ;Davison & Barnes, 1998 underlying the phytotoxicity of the pollutant. Yet, despite more than 40 yr of research, many fundamental questions remain unanswered (Runeckles & Chevone, 1992 ;Heath & Taylor, 1997).…”

The effects of nutrient limitation on the response of Plantago major to ozone

“…Most experiments on wild plants have used nutrient-rich composts or soils in which none of the major nutrients were limiting (Mortensen & Nilsen, 1992 ;Pearson et al, 1996 ;Lyons & Barnes, 1998). However, most natural and semi-natural communities exist on soils in which growth is limited by nutrients, toxic metals or anoxia.…”

Patterns of molecular genetic variation in Plantago major and P. intermedia in relation to ozone resistance

“…The study also demonstrates that some wild species may be able to adapt to higher ground-level O $ concentrations, and this may be reflected in changes in genetic composition. It has been reported that fitness of O $ -sensitive genotypes in the wild is possibly lower due to the production of less seed (Whitfield et al, 1996 ;Lyons & Barnes, 1998) and\or due to lower competitive ability, especially in the early phases of life (Berrang et al, 1988).…”