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To clarify the relationship between cultivar difference in the sensitivity of net photosynthesis to ozone (O(3)) and the reactive oxygen species (ROS) scavenging system in wheat (Triticum aestivum), we investigated the effects of chronic exposure to ambient levels of O(3) on gas exchange rates, activity and concentration of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco), activity of ROS scavenging enzymes and concentration of antioxidants of the flag leaf in two Japanese winter wheat cultivars (Norin 61 and Shirogane-komugi). Although the net photosynthetic rate of the flag leaf in Norin 61 was not significantly reduced by exposure to O(3), that in Shirogane-komugi was significantly reduced by the exposure to O(3) during the anthesis and early grain-filling stages. In the two cultivars, stomatal diffusive conductance to H(2) O of the flag leaf was not significantly affected by the exposure to O(3). The exposure to O(3) induced significant reductions in the activity and concentration of Rubisco, activities of catalase (CAT) and monodehydroascorbate reductase (MDAR) and concentrations of reduced form of ascorbate and total glutathione of the flag leaf in Shirogane-komugi. It was concluded that the sensitivity of net photosynthesis of flag leaf to O(3) is higher in Shirogane-komugi than in Norin 61, and the difference in the sensitivity to O(3) between the two cultivars is mainly due to that in the effects of O(3) on the detoxification ability of ROS, mainly determined by the activity of ROS scavenging enzymes, such as CAT and MDAR.

The response of BARI Sunflower-2 (Helianthus annuus L.) to sodium chloride (NaCl) at germination and early seedling growth was investigated. The seeds and seedlings of sunflower were treated with a series of eight different concentrations of NaCl viz 25, 50, 75, 100, 125, 150, 175 and 200 mM and distilled water (control) and were allowed to grow under plate culture condition. The results showed that the highest salinity concentration (200 mM NaCl) remarkably decreased the germination percentage, germination index and speed of germination of BARI Sunflower-2. Fresh and dry masses of both shoot and root were significantly reduced at a 25-200 mM NaCl solution. Significant reductions of shoot and root length were also noted with the increase of NaCl concentration. The results also illustrate that up to 50 mM NaCl concentration, all of the germination indices and fresh and dry biomass were withstand more than 70%. Thus the present study concluded that the BARI Sunflower-2 could be cultivated in moderately saline soil.