Regulating Action Of Climate Factors To Stress Effects Of Ozone On Winter Wheat By Field Experiment And Modeling

The effect of increasing tropospheric ozone concentration on terrestrial ecosystems has become one of the hottest research fields at home and abroad. Further research about crops response to ozone stress in different regions and climatic conditions, has important scientific significance and application value on understanding the negative effects of tropospheric ozone comprehensively, and improveing and perfecting evaluation technology of crop yield losses. Based on an analysis of the accumulated data of the open top chamber experiments in Jiangsu Nanjing and Hebei Gucheng, this paper studied the indicators of growth and physiological indexes of winter wheat, that lived in the different climate conditions, with the difference of the response characteristics in different ozone concentration. In addition, by using the simulation model of stomatal conductance model and ozone uptake flux model, this paper revealed the physiological mechanism of the differences between the north and south on the response of fluxes, such as ozone absorption effective dose. Thus the paper thoroughly discussed regulatory role of regional climate on ozone stress. The main conclusions of this paper are as follows:(1) Under the stress of elevated03(100nL·L-1、150nL·L-1) in these two places, the winter wheat was growing in an anomalous way, such as growth stages and filling period reductions, accelerated senescence. That was one of the major reasons for the crop reduction.The delaying effect in Nanjing started from the heading stage, and represented slight premature ageing in flowering stage; the delaying effect in Hebei extends into the flowering stage, then showed a fast aging and a premature mature period.(2) As a result of the stress of elevated03(100nL·L-1、150nL·L-1) in these two places, the height and leaf area of winter-wheat had significant diminishment. Over the whole cropping season, the height and leaf area of winter-wheat in Nanjing with100nL·L-1&150nL·L-1had a smaller drop than the data in Gucheng, compared with CK. Through the growing stage, the leaf area under the150-treatment strongly displayed growth inhibition.(3) In the whole growing stage, compared with control, the dry weight of root, leaf and ear were general declined under the O3stress. The dry weight of root under100nL·L-1treatment in the blooming stage increased firstly, then decreased rapidly until the mature stage, compared with control (CK).(4) From the jointing stage to the booting stage, compared with control, the chlorophyll content and the carotenoid content with100nL·L-1treatment increased in varying degrees in both north and south, the increase rate in Nanjing was bigger than that in Gucheng;150nL·L-1treatments, leaf chlorophyll content decreased compared with control. From the blooming stage to the booting stage, the chlorophyll content and the carotenoid content kept fallen, and got the maximum downtrend in the filling stage. Compared with the data in South, the ozone stress in Gucheng in North was much bigger.(5) The rate of decreasing of gas exchange parameters which were under O3stress in South and North had increased firstly and then decreased in the trend. During the whole growth stages, O3cound inhibit effect of the net photosynthetic rate and the stomatal conductance. The variation trend of intercellular CO2concentration and stomatal limitation value was not regular. The drop of the net photosynthetic rate and the conductance of stomata, compared with CK, under the treatment of100nL·L-1&150nL·L-1in Gucheng in North was much bigger than the drop in Nanjing in South. With special difference in some growth period,the power of ozone stress with100nL·L-1treatment in Gucheng was bigger than that with150nL·L-1treatment in Nanjing. (6) Before the flowering stage, the temperature is the major factor limiting of stomatal conductance, and temperature restriction in Hebei is larger than that in Nanjing; After flowering, the vapor pressure deficit gradually become the main factor limiting. The influence of radiation stress on the stomata conductance is obvious difference between Nanjing and Hebei. Due to the pores are the main channel of the gas into the crop body, the impact on stomatal conductance is directly related to ozone absorption effective dose, then the difference of climate conditions between south and north would lead to different ozone absorption flux.(7) During ozone fumigation, the O3accumulated uptake flux of ck,100nL·L-1and150nL·L-1was8.4、14.47.15.49mmolO3·m-2and10.63、14.8、15.75mmolO3·m-2respectively in Nanjing and Gucheng. In Nanjing city, the relationship between the relative value of dry matter accumulation(y) and the accumulated uptake flux (x) is’y=1.997-0.0871*x,(R2=0.5772). Comparatively in Hebei Province, the relationship is’y=2.2836-0.113*x,(R2=0.6522). Flux model which is synthesizing climate factor clear indicated that ozone stress in Hebei was higher than which in Nanjing, revealed the climate adjustment mechanism of the differences in winter wheat growth and physiological characteristics between the north and south region. The main adjustment factor was vapour pressure defict and temperature.