浑善达克沙地固沙先锋豆科植物的光合特性

Photosynthesis Characteristics of a Sand-fixing Pioneer Legume in Hunshandake Sandland

豆科植物木岩黄芪是浑善达克沙地的优势种,也是流动沙丘的先锋种,研究其对沙丘恶劣生境的光合适应性有助于揭示固沙植物的适应性机制,为其在沙地恢复中的充分利用提供理论依据。研究了木岩黄芪的光合特征、资源利用效率、PSII光化学效率以及光合酶活性。结果表明,木岩黄芪的光合速率、水分和氮素利用效率较高,忍受中午强光和高温的能力强,还表现出了显著的高的光饱和点和低的光补偿点,气孔和非气孔调节能力强,属于低耗水型植物;C4光合酶的活性高,但稳定性碳同位素的测定结果显示木岩黄芪是C3植物,因此木岩黄芪可能属于C3和C4植物的中间类型。C4光合酶作用下的高羧化效率和高资源利用效率以及固氮优势使得该物种对沙丘的恶劣生境适应性较强。

Hedysarum fruticosum var. lignosum is a superior species in the sand dunes of Hunshandake Sandland. Exploring the photosynthetic characteristics of this species will be helpful to reveal the adaptive mechanisms of the pioneer species in the sandy environment. The photosynthetic characteristics of H. fruticosum var. lignosum are monitored and compared with those of Sallx gordejevii, a typical C3 species co-existing with H. fruticosum in semi-fixed or fixed sand dunes. The maximal photosynthetic rate （Pmax） and water use efficiency of H. fruticosum are approximately one times higher than that of S. gordejevii. H. fruticosum could endure high light and temperature at noon and has a high light saturation point and a low light compensation point. Except Ribulose-1.5-bisphosphate carboxylase （RuBPcase）, the activities of photosynthetic carbon assimilation enzymes, such as phosphoenolpyruvate carboxylase （PEPcase）, NAD-malic enzymes （NAD-ME）, NADP-malic enzymes （NADP-ME）, NAD-malate dehydrogenase （NAD-MDH）, NADP- malate dehydrogenase （NADP-MDH）, and pyruvate phosphate dikinase （PPDK）, in H. fruticosum are at least four times greater than that in S. gordejevii, it is suggested that H. fruticosum might have a C4 photosynthetic syndrome. However, the stable carbon isotope analysis reveals that H. fruticosum has the δ3C value of -23×10^-3, which is closed to that of C3 plants. Therefore, it is likely that H. fruticosum is either a C3-C4 intermediate species, or a C3 species displaying C4 metabolic characteristics in the habitat of sand dune. The involvement of C4 metabolism in H. fruticosum might account for its greater efficiencies for photosynthesis and water use, and allows H. fruticosum to colonize the shifting sand dune with high temperature, light intensity, and water stress.