Abstract
The cultivar difference in the sensitivity of Brassica campestris L. to O3 based on the dry weight growth was investigated using the 10 cultivars. On the 8th, 10th and 12th days after sowing, 10 cultivars were exposed to 130±10nl·l-1 (ppb) O3 for 4h per day (10: 00-14: 00) at 29.0±1.0°C, 65±10% R. H. and 400μmol·m-2·s-1 PPFD. The control plants were exposed to charcoal-filtered air under the same environmental conditions. On the 15th day after sowing, all the plants were harvested to determine leaf area and dry weight.
The sensitivity of the 10 cultivars to O3 based on the percent reduction in the total dry weight per plant to the control value was ranked as follows: Misugi>Purara>Shinbansei>Maruba>Bansei=Rakuten>Gozekibansei>Harumi>Natsurakuten>Saori. This ranking could not be explained by the degree of O3-induced visible foliar injuries, whole-plant growth rate and stomatal density. However, the reduction in the photosynthetic CO2 uptake per unit amount of O3 absorbed by the leaf was significantly different among the three cultivars, and was ranked as follows: Misugi>Harumi>Saori. This ranking coincided with that in the sensitivity of whole-plant dry weight growth or net photosynthetic rate to O3. Therefore, the cultivar difference of Brassica campestris L. in the sensitivity to O3 based on the dry weight growth is considered to depend mainly on the capacity for physiological detoxification of O3 in the leaves.
