不同氮素条件米槁幼苗光合作用对CO_2响应特征

Response characteristic of Cinnamomum migao seedling's photosynthesis to CO_2 in different conditions of nitrogen

为探求氮素对米槁幼苗叶片CO_2响应特征影响,以1年生米槁幼苗为试验材料,采用砂培法,利用Li-6400光合仪测定4种不同氮浓度胁迫下米槁叶片CO_2响应曲线及气孔导度(Gs)、胞间CO_2浓度(Ci)、蒸腾速率(Tr)等相关光合参数,并运用直角双曲线、非直角双曲线、直角双曲线修正3种模型拟合米槁叶片CO_2响应曲线。结果显示,直角双曲线修正模型拟合米槁叶片CO_2响应曲线,可克服直角双曲线模型未考虑曲线凸度缺陷及无法拟合CO_2过饱和净光合速率(Pn)下降缺点,得到光合参数与实测值相近,直接确定CO_2饱和点(CSP)。在控制外界条件下,各氮处理米槁Ci随叶室内CO_2浓度(Ca)升高呈同步直线上升趋势。同一Ca值下,米槁叶片Ci随氮浓度水平增加而增大。各氮处理下米槁叶片Gs随Ci升高总体呈下降趋势;Tr变化趋势与Gs一致,在同一Ci下,Gs与Tr均随氮浓度增大而增加。米槁叶片Pn随Ci升高逐步升高,但在高Ci阶段Pn略下降,增施氮素可提高米槁叶片CSP、最大净光合速率(Pnmax),降低叶片CO_2补偿点(CCP),表明增施氮素能可强米槁叶片光合作用对CO_2适应幅度,提高CO_2利用效率,促进有机物积累。研究表明,直角双曲线修正模型拟合米槁叶片CO_2响应曲线效果最佳,施氮可有效促进米槁幼苗生长。

To exploring the effect of nitrogen on C02 response Characteristics of Cinnamomum migao leaf. This research determined the CO2 response curve of migao leaf and a series of related photosynthetic parameters which including stomatal conductance（Gs）, intercellular CO2 concentration （C）, transpiration rate （Tr） by used Li-6400 portable Photosynthesis System, and fitted the CO2 response curve of migao leaf by used three models of rectangular hyperbola, non-rectangular hyperbola, modified rectangular hyperbola under the stress of four different concentration of nitrogen. Result showed that：the modified rectangular hyperbola models make up the defect from the rectangular hyperbola models do not consider the curve convexity and do not fit phenomena of CO2 supersaturation＇s and Net photosynthetic rate （P,）＇s decline, it＇s photosynthetic parameters close to measured values, obtained CO2 saturation point （CSP） directly. C~ of each migao treated by nitrogen with the increase of leaf chamber CO2 concentration （Ca） appeared a linear upward trend consistently under controlled ambient conditions. C, increased with the increased concentration of nitrogen and phosphorus at the same value C,. The change trend of Tr and G, almost unanimously that performed with the increase of C, appeared downtrend totally, and with the increase of concentration of nitrogen or performed increasing trend under the same C,. P, increased gradually as C, increases excepted for that P, declined slightly in high stage of C,, CSP and Maximum net photosynthetic rate （Pnmax） have been improved and CO2 compensation point （CCP） have been reduced in adding Nitrogen, This phenomena indicated that the adaptation of amplitude from photosynthesis of migao leaf to CO2 can be enhanced, the efficiency of CO2 utilization can be improved, the accumulation of organic matter can be promoted by adding nitrogen, the modified rectangular hyperbola models are the best on fitted the CO2 response curve of migao, the growth of migao＇s seedling can be promoted by adding nitrogen effectively.