Ozone affects gas exchange, growth and reproductive development in Brassica campestris (Wisconsin fast plants).

Exposure to ozone (O(3)) may affect vegetative and reproductive development, although the consequences for yield depend on the effectiveness of the compensatory processes induced. This study examined the impact on reproductive development of exposing Brassica campestris (Wisconsin Fast Plants) to ozone during vegetative growth. Plants were exposed to 70 ppb ozone for 2 d during late vegetative growth or 10 d spanning most of the vegetative phase. Effects on gas exchange, vegetative growth, reproductive development and seed yield were determined. Impacts on gas exchange and foliar injury were related to pre-exposure stomatal conductance. Exposure for 2 d had no effect on growth or reproductive characteristics, whereas 10-d exposure reduced vegetative growth and reproductive site number on the terminal raceme. Mature seed number and weight per pod and per plant were unaffected because seed abortion was reduced. The observation that mature seed yield per plant was unaffected by exposure during the vegetative phase, despite adverse effects on physiological, vegetative and reproductive processes, shows that indeterminate species such as B. campestris possess sufficient compensatory flexibility to avoid reductions in seed production.

Tansley Review No. 115: Impact of ozone on the reproductive development of plants.

Sexual reproductive development is a crucial stage in the life cycle of higher plants as any impairment of the processes involved might have significant implications for the productivity of crop plants and the survival of native species. There is considerable evidence that exposure to ozone, even at current ambient levels in many industrialized countries, reduces grain and fruit yields and adversely affects yield quality. It is also well established that sensitivity to ozone may differ not only between species, but also between cultivars and populations of individual species, and that the impact of exposure is highly dependent on ozone concentration and the duration and timing of exposure. However, few studies have attempted to distinguish between the direct effects of air pollutants on reproductive development, and indirect effects mediated by injury to the vegetative organs and associated changes in the supply of assimilates and other essential resources to support reproductive growth, or the levels of endogenous growth regulators. This review considers the impact of ozone on the reproductive biology of agricultural and native species, and examines its direct effects on specific reproductive processes. The extent to which compensatory responses redress the adverse effects of exposure is also explored, with particular reference to recent studies of Brassica napus (oilseed rape), Brassica campestris (Wisconsin Fast Plants), Plantago major (greater plantain) and Triticum aestivum (wheat). contents Summary 421 I. introduction 421 II. effects of ozone on reproduction 423 III. influence of reproductive habit and implications for field-grown plants 438 IV. conclusions and future research 441 Acknowledgements 442 References 442.