Assessment of loss of accumulated dry matter in winter wheat based on stomatal conductance and ozone uptake model
基于气孔导度和臭氧吸收模型的冬小麦干物质累积损失评估

To in-depth understand the injury of increased ozone concentration at surface to winter wheat, the Open-Top Chamber(OTC) is used to make field experiment, in which investigated are temperature, sunshine duration and vapor pressure difference (VPD) in various phases of growth, together with their difference in stages and impacts of ozone stress explored. Change in stomatal conductance are calculated by means of the Jarvis-type factorial model of stomatal conductance improved by Pleijel et al.(2007) and the calculation if compared with the daily variation in conductance in the flowing stage. Results show that the model is applicable to the assessment of the effects of local ozone increase upon winter wheat. Besides, the model of ozone absorption flux is utilized to compute the accumulative uptake flux AFst06 for the whole growth periods at daily ozone absorption flux higher than 6nmol·m-2, which is used to construct its relationship with the response to the loss of dry matter accumulated during the entire growth/development stage. Analysis suggests that the coefficient of determination is 0.91and 0.93(P<0.01) between AFst06 treated by 150nL·L-1 and 100nL·L-1 during the O3 smudging and the relative value of dry matter accumulation in winter wheat in different stages, respectively, both figures in high correlation. For the increase in AFst06 by 10mmol·m-2, the treatments of 150nL·L-1 and 100nL·L-1 compared to CK show the loss of dry matter to be 16.41% and 13.23%, respectively. Also, discussion if made of merits and demerits of different assessment methods and the strength of with the flux response assessment model under O3 stress as well as the effect of vapour pressure differences(VPD) and other upon stomatal conductance and O3 uptake flux. This research provides a new means for comprehensive evaluation of surface ozone increase influencing photosynthesis productivity of winter wheat and its yield formation conducted in China, and it thus of practical significance to the assessment of the intensification of surface ozone concentration impacting on food crop security in our country.