不同施氮量对杂交酸模叶片光合电子流分配的影响

研究了不同施氮量对高蛋白含量植物杂交酸模(Rumex patientiaxR.tianschanicus)叶片中总光合电子流和分配在碳同化、光呼吸、Mehler反应以及氮代谢上的光合电子流的影响,并研究了不同施氮量对硝酸还原酶(NR)和谷氨酰胺合成酶(GS)的活性、叶片的蛋白质含量及叶绿素含量的影响。结果表明随着施氮量的增加,硝酸还原酶和谷氨酰胺合成酶的活性都显著提高,同时更多的光合电子流分配到氮代谢和光呼吸。氮代谢所需光合电子流约占总光合电子流的15%～21%。缺氮并没有造成光合电子流向Mehler反应分配的增加。

Effects of Different Nitrogen Application Rate on Allocation of Photosyn- thetic Electron Flux in Rumex K-1 Leaves

The total photosynthetic electron flux through PSII [J(e) (PSII)], the electron flux used for carbon assimilation [J(e) (PCR)], the electron flux used for photorespiration [J(e) (PCO)], the electron flux used for Mehler reaction [J(a) (O(2)-depend)] and the electron flux used for nitrogen metabolism [J(a) (O(2)-independ)] in leaves of Rumex K-1, a fodder crop with high protein content, were measured under three levels of nitrogen application (Fig.2). The nitrate reductase (NR) activity, glutamine synthetase (GS) activity, the leaf protein content, the chlorophyll content, P(n) and Phi (PSII) and F(v)/F(m) (Table 1) were also measured. The results showed that with the increase of nitrogen application, the NR and GS activities increased remarkably (Fig.3) and more electron flux was allocated to nitrogen metabolism as well as photorespiration (Fig.2). Nitrogen metabolism and carbon metabolism competed for energy, and the proportion of energy used in nitrogen metabolism to that used in carbon metabolism changed with nitrogen application rate. The electron flux used for nitrogen metabolism is about 15%-21% of the total electron flux under the three levels of nitrogen application (NO(3)(-) 0-30 mmol/L). Under lower nitrogen application, though energy used for carbon and nitrogen assimilation remarkably decreased, no significant increase of electron flux allocated to Mehler reaction was observed. The excess excitation energy in the leaves under the lower nitrogen application was efficiently dissipated via other energy dissipation mechanisms to protect the leaves against photo-damage.