Pearcy Robert W, Ustin Susan L
Department of Botany, University of California, 95616, Davis, CA, USA.
Oecologia. 1984 Apr;62(1):68-73. doi: 10.1007/BF00377375.
The comparative responses of photosynthesis and growth to salinity were investigated for two C and one C species native to the tidal marshes of the San Francisco Bay-Sacramento River estuary of Northern California. At low salinities (0 or 150 meq l), where photosynthetic rates were maximal for all species, the C grass Spartina foliosa maintained the highest photosynthetic capacity and the C stem-succulent shrub Salicornia virginica the lowest; photosynthetic rates of the C sedge Scirpus robustus were intermediate. Differences in photosynthetic responses to intercellular CO pressure and temperature were consistent with those generally observed between C and C plants.CO uptake was reduced at salinities above 150 meq l in Scirpus and 300 meq l in Spartina. In contrast, Salicornia exhibited no inhibition of CO uptake even at 450 meq l salinity. Analysis of the responses to intercellular CO partial pressures showed that the inhibition of photosynthesis by high salinity in both Spartina and Scirpus is primarily accounted for by reduced photosynthetic capacity of the mesophyll, and secondarily, by reduced leaf conductances.Species differences in relative growth rate (RGR) almost exactly opposed the differences in photosynthetic rates; the highest RGR was found in Salicornia and the lowest in Spartina. This reversal is accounted for by the greater allocation to photosynthetic shoots in Salicornia, which more than compensated for the lower photosynthetic capacity per unit surface area. RGR was more sensitive to salinity than photosynthetic rate in all three species, but the same relative sensitivities held. For Scirpus, reduced leaf elongation rates and changes in allocation patterns account for the greater limitation by salinity of RGR than of photosynthesis, and may be a primary factor restricting productivity of this species in saline habitats.
对原产于北加利福尼亚旧金山湾 - 萨克拉门托河河口潮汐沼泽地的两种C₃植物和一种C₄植物的光合作用和生长对盐分的比较响应进行了研究。在低盐度（0或150 meq l）下，所有物种的光合速率均达到最大值，C₃草本植物互花米草保持最高的光合能力，C₄茎肉质灌木弗吉尼亚海蓬子最低；C₃莎草粗壮藨草的光合速率居中。对细胞间CO₂压力和温度的光合响应差异与C₃和C₄植物之间通常观察到的一致。在盐分高于150 meq l时，粗壮藨草的CO₂吸收减少，互花米草在盐分高于300 meq l时CO₂吸收减少。相比之下，即使在盐度为450 meq l时，海蓬子也未表现出对CO₂吸收的抑制。对细胞间CO₂分压响应的分析表明，高盐度对互花米草和粗壮藨草光合作用的抑制主要是由于叶肉光合能力降低，其次是叶片导度降低。相对生长速率（RGR）的物种差异几乎与光合速率的差异完全相反；海蓬子的RGR最高，互花米草最低。这种逆转是由于海蓬子对光合枝的分配更多，这超过了单位表面积较低光合能力的补偿。在所有三个物种中，RGR对盐分比光合速率更敏感，但相对敏感性相同。对于粗壮藨草，叶片伸长率降低和分配模式变化导致盐分对RGR的限制大于对光合作用的限制，这可能是限制该物种在盐生栖息地生产力的主要因素。
