2011 年 67 巻 1 号 p. 21-32
To predict the yield losses in winter wheat due to the elevated ozone concentration in eastern China, we tested the ozone dose response functions (O3DRF), i.e. the relationship between the accumulated stomatal ozone flux above a threshold of 6 nmol m-2 s-1 (AFst6) and the relative grain yield (RY), via observations of three cultivars of winter wheat in a FACE-Ozone (free-air concentration enrichment with ozone) experiment. We also presented a new O3DRF based on the new ozone dose using the FACE-Ozone results.
The AFst6 was calculated by applying the flag leaf stomatal conductance model of each cultivar developed in this study. The observed RY fell below the linear O3DRF: ‘RY (%)=100-4.8 AFst6’, which has been derived in Europe and widely used (Pleijel et al., 2000; 2007), at higher AFst6. This deviation was due to the synergetic effect of the accelerated drop in photosynthesis and the decelerated increase of AFst6 caused by the stomatal closure at a higher ozone dose. We therefore presented a curvilinear O3DRF: ‘RY (%)=100-k (AFst6)l’ for the wheat cultivars in the FACE-Ozone experiment.
We also explored the applicability of the relative net primary productivity (NPP) of the flag leaf canopy (RNPPc) as a better ozone dose than AFst6. The NPP of the flag leaf was calculated by applying the flag leaf photosynthesis model developed in this study for each cultivar. The relationship between RNPPc and RY of the three cultivars showed good correlation, suggesting that RNPPc could be used as O3DRF to predict RY or the yield loss due to the increased ozone concentration.
