Speaker
Description
Background and objectives
Global tropospheric ozone concentrations have increased over the past two to three decades, especially in the Northern Hemisphere, tropical regions, and rapidly developing areas such as East Asia and India. Absorbed ozone can negatively affect plant growth by generation internal oxidative stress. Light is important for plant growth and can in theory modify ozone effects. To little light might increase ozone effects due to less energy for the ozone damage repair processes, too much light might also increase ozone effects due to oxidative stress created by the high light input while medium light might give enough energy for growth and damage repair only by giving little additional stress. Plant leaves are usually exposed transient to variable light levels in nature over the day and season, due to solar angle and direction, weather, leaf angles, shading by other leaves, movements by wind, etc. This study experimentally examines, across two separate experiments, the ecophysiological responses and dry-matter accumulation of several crop species exposed ozone along a light gradient
Methods
In a newly rebuilt Ecotron (Ecotron DTU) five different species (tomato, soybean, potato, beetroot and radish) were grown in 9 l well-watered pots with nutrient-enriched peat soil from seed/seed potato to maturity. The pots were positioned on tray tables and up to 18 pots were exposed to PAR light ranging from 200 to 1100 μmol m⁻² s⁻¹ in two large chambers. The ozone concentrations averaged 100 ppbv in the ozone-enriched treatment and 8 ppbv in the control. The day/night environmental conditions were kept constant across treatments, with a 16/8 h photoperiod, 22/19 °C temperature regime, and 50/50 % relative humidity. Only artificial LED lighting was used in the chambers. Leaf-level measurements of gas exchange, chlorophyll fluorescence, and pigment composition were conducted throughout the experiment.
Preliminary results
The experiments indicate clear interactions between light intensity and ozone responses, showing that chronic ozone exposure reduces yield even under moderate irradiance. They also reveal substantial inter-crop variation in physiological sensitivity to ozone.
Keywords: Ecotron DTU, gas exchange, leaf pigments, ozone, PAR gradient.
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