空气NH_3增高情况下不同形式氮源对荫香光合作用和氮利用的影响

PHOTOSYNTHESIS AND NITROGEN UTILIZATION IN LEAVES OF CINNAMOMUM BURMANNI GROWN UNDER ELEVATED ATMOSPHERIC NH_3 CONCENTRATIONS AND SUPPLIED WITH DIFFERENT FORMS OF SOIL N

生长在供给NO-3 N、NH+ 4 N和NH4NO3 N氮源下的荫香 (Cinnamomumburmanni)幼树暴露在增高空气NH3浓度下 30d。利用气体交换测定和氮分析研究了植株的光合作用、氮利用和氮在光合过程一些组分中的分配 ,根据Farquhar_vonCaemmerer模式得出相关光合参数。结果表明在增高空气NH3 下生长于NO-3 N的植株Rubisco最大羧化速率 (Vcmax)和最大光合电子传递速率 (Jmax)较正常空气下的高 ,但生长于NH+ 4 N和NH4NO3 N的植株则较正常空气下的低。无论生长于何种形式氮下的植株 ,在空气NH3 增高下以单位叶面积为基准的叶氮含量 (Na)显著增高 (p <0 .0 5 )。在增高空气NH3 下 ,生长于NO-3 N下的植株 ,其类囊体氮量 (NT)、Rubisco氮 (NR)和结合于光合电子传递链的氮 (NE)的含量较正常空气下的增高 (p <0 .0 5 ) ;而生长于NH+ 4 N和NH4NO3 N下的植株则较正常空气下的低。表明在空气NH3 增高下生长于NO-3 N的植株能有效地利用氮合成光合过程必要的组份 ,而生长于NH+ 4 N和NH4NO-3 N的植株氮在NT、NR 和NE 的分配受到部分限制。在空气NH3 增高下生长于NO-3 N和NH4NO3 N的植株 ,其以单位干重为基准的有机氮量较正常空气下的高 ,但生长于NH+ 4 N的植株则较正常空气下的低 ,此外在空气NH3 增高下生长于NO-3 N?

We investigated the effects of different forms of soil nitrogen additions (NO - 3-N, NH + 4-N or NH 4NO 3-N) and exposure to elevated atmospheric NH 3 concentrations on photosynthesis, nitrogen utilization and nitrogen allocation in photosynthetic components in leaves of Cinnamomum burmanni. The results showed that maximum rates of carboxylation (V cmax) and maximum rates of potential electron transport (J max) were achieved in plants grown with additions of NO - 3-N and under elevated atmospheric NH 3 concentrations compared to plants growing under ambient conditions. Both J max and V cmax declined in plants supplied with NH + 4-N or NH 4NO 3-N and grown under elevated atmospheric NH 3. Regardless of the different forms of nitrogen supply, leaf nitrogen content on an area basis (N a) significantly increased under elevated atmospheric NH 3 concentrations (p<0.05). Thylakoid nitrogen (N T), Rubisco nitrogen (N R) and nitrogen associated with electron transport (N E) increased significantly in plants supplied with NO 3 --N and exposed to the elevated atmospheric NH 3 when compared to plants grown under ambient condition (p<0.05); however, N a, N T, N R and N E all decreased in plants supplied with NH + 4-N or NH 4NO 3-N. These results suggest that increased atmospheric NH 3 promotes the utilization of nitrogen for the synthesis of photosynthetic components, but inhibits the partitioning of nitrogen to N T, N R, and N E in plants supplied with NH + 4-N or NH 4NO 3-N. The organic nitrogen content per unit dry mass increased in plants that were supplied with NO - 3-N or NH 4NO 3-N (but not NH + 4-N) when exposed to increased atmospheric concentrations of NH 3. The soluble protein nitrogen content also increased in plants grown with NO - 3-N additions but not in plants grown with additions of NH + 4-N. The results suggest that increased atmospheric NH 3 concentration enhances nitrogen absorption and utilization and promotes photosynthesis in plants supplied with NO - 3-N additions but inhibits photosynthesis and nitrogen in plants supplied with NH + 4-N or NH 4NO 3-N.