Production Practices and Quality Assessment of Food Crops. Vol. 1

IMPACT OF OZONE ON CROPS
S. DEL VALLE-TASCON AND J. L. CARRASCO-RODRIGUEZ
Departamento de Fisiologia Vegetal, Fac. Ciencias Biológicas, Universidad de Valencia,
C/. Dr Moliner 50, 46100 Burjasot (Valencia), Spain
1. INTRODUCTION
Ozone (O 3) is regarded as one of the most damaging air pollutants to which plants
are exposed (Thompson, 1992). Over large rural areas of industrialized countries,
its average monthly concentration increased during the last century to between 20
and 80 ppb (Lucas et al., 1993; Heath, 1994a). During episodes of severe air
pollution, concentrations as high as 400 to 500 ppb have been monitored (Seinfeld,
1989). Ozone is a secondary pollutant resulting from photochemical reactions
(mainly volatile organic compounds and nitrogen oxides). Under favourable meteorological
conditions, ozone may accumulate in the troposphere and reach a level
that causes significant decrease in growth and yield of ozone-sensitive species in
many parts of the world. The problem of phytotoxicity is well established in Europe
(Jäger et al., 1992) and North America (Heck et al., 1988). More recently, high
concentrations of ozone have also been measured (Wahid et al., 1995).
Ozone enters the leaves through the stomata and diffuses within the apoplast.
In this microenvironment it is intensively reactive and produces high levels of
toxic compounds such as hydroxyl and superoxide radicals, hydrogen peroxide
and other reactive oxygen species (Heath and Taylor, 1997; Pell et al., 1997).
These active oxygen species react with proteins, lipids, and plasma membrane.
Antioxidative defence activity systems may prevent this damage. Impact on plant
crop yield ranges from minimal visible symptoms to substantial inhibition of productivity,
including reduced photosynthetic capacity, enhanced rate of maintained
respiration, and increased retention of fixed carbon in source leaves (Lefohn, 1992;
Alscher and Wellburn, 1994). These plant responses can affect the plants’ abilities
to respond to further stress attacks. The action of ambient O 3 on the plant defence
system enhances attack by pathogens but may lead to induce resistance (Sandermann
et al., 1998). In addition, the impact of O 3 is profoundly influenced by other environmental
factors.
Agricultural yield loss in the USA is approximately 1 to 2 billion dollars each
year (US EPA, 1998). In addition to this considerable yield reduction, damaging
of forest ecosystems and a reduction of lung functions in healthy people and people
with an impaired respiratory system have been demonstrated. Despite the economic
significance of these effects on crops, the mechanisms of the action of O 3 are still
poorly understood.
A number of points discussed below have been described in an earlier review that
describes the role of O 3 in phytotoxicity (Laurence and Weinstein, 1981; Gunderian,
1985; Heagle, 1989; Treshow and Anderson, 1989; Smith, 1990; Sandermann,
1996).
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R. Dris and S. M. Jain (eds.), Production Practices and Quality Assessment of Food Crops,
Vol. 1, “Preharvest Practice”, pp. 189–208.
© 2004 Kluwer Academic Publishers. Printed in the Netherlands.