空气 NH3增高和不同氮源供应下大叶相思叶片光合参数的变化

生长在空气 NH3增高下 45 d的 NOˉ3- N大叶相思植株 ,其光饱和光合速率较对照的植株高 ;而生长在空气 NH3增高下的 NH 4- N和 NH4 NO3- N的大叶相思 ,当光强在 70 0 μmol·m- 2 ·s- 1左右时 Pn 达到最大值 ,较对照植株的要高。而当光强 >70 0 μmol·m- 2·s- 1时 ,Pn 降低 ,且较生长在对照条件下的低。表明在空气 NH3增高下生长的 NH 4- N和 NH4 NO3- N植株 ,其净光合速率 Pn会受到强光抑制。空气 NH3增高并不明显改变光呼吸 ( Rd)和无光呼吸下的 CO2 补充点 (Γ* )。无论生长在何种氮源下的大叶相思 ,其最大Ru BP饱和羧化速率 ( Vcmax)和最大电子传递速率 ( Jmax)均较生长在对照植株的高 ( P<0 .0 5 ) ,其叶氮含量亦较高 ( P<0 .0 5 ) ,其碳氮比较对照的低。在空气 NH3增高下 ,无论何种氮源生长的大叶相思 ,其 PR和 PB明显高于对照的植株 ,表明大叶相思能从空气 NH3中摄取和同化氮 ,增加氮积累和有利于 Rubisco和电子传递组分的合成 ,增高光合速率。空气 NH3增高可能有利于 Rubisco和电子传递组分的合成 ,在较低光强下能增高光合速率。空气 NH3增高可能有利于退化生态系统的生态恢复过程中的氮积累和先锋植物的早期生长。

Variations of photosynthetic parameters in leaves of Acacia auriculaeformis grown in different nitrogen sources under increased atmospheric NH3

Higher light-saturated photosynthetic rate was observed for the NOˉ3-N plants of Acacia auriculaeformis under elevated atmospheric NH3 in comparison with that grown in control. As the irradiance intensity reached about 700μmol*m-2*s-1, the maximum rate of photosynthesis occurred in leaves of NH+4-N and NH4NO3-N plants of A. auriculaeformis in the elevated NH3, and higher than that of the plants grown in control. When irradiance intensity was higher than 700μmol*m-2*s-1, their net photosynthetic rate (Pn) decreased and even lower than that in control. It may suggest that higher light intensity restrict Pn of NH+4-N and NH4NO3-N plants grown in the elevated NH3. There were no significant effects of increased NH3 on the mitochondrial respiration rate in the light (Rd) and the CO2 compensation point in the absence of Rd (Γ*). The maximum RuBP-saturated rate of carboxylation (Vcmax) and the maximum rate of electron transfer (Jmax) in plant of A. auriculaeformis supplied with different nitrogen sources and grown in increased atmospheric NH3 were higher than those in control(p<0.05), and so was the leaf N content(p<0.05). Lower C/N ratio was found in plants grown in the elevated NH3. However, the leaf N investment in carboxylation capacity (PR) and N investment for the capacity of electron transport (PB) in the plants grown in the elevated NH3 with different N sources were higher than those of the control. It shows that more nitrogen was acquired by plants from the atmosphere with elevated NH3 and it favors the syntheses of Rubisco and composition of electron transport chain. Increased atmospheric N deposition would facilitate nitrogen accumulation and early growth of plants in the process of vegetation restoration.