中科院：藜科中新的C3-C4中间型植物及其碳同化机制

C3-C4中间型植物一直受到研究学者的关注，与C3植物相比，C3-C4中间型植物在叶片解剖结构和光合生理上具有很多中间型的性状，研究它们有助于了解C4植物的进化以及光呼吸减少的机制。

中国科学院新疆生态与地理研究所干旱区生物地理与生物资源重点实验室闻志彬在前期的研究中发现藜科猪毛菜属中松叶猪毛菜具有类似C3-C4中间型的解剖结构，但其δ13C值为-22.062‰，处于C3植物δ13C值的范围(-21‰~-30‰)，它是C3植物还是C3-C4中间型植物值得深入研究。进一步的研究表明，它的叶片解剖结构具有类似C3-Sympegmoid型的2-3层叶肉细胞，但是与C3-Sympegmoid型相比，具有更加明显并且类似于C4-Kranz结构的维管束鞘细胞，低的叶肉细胞和维管束鞘细胞的比值，更多的维管束鞘叶绿体细胞，并且维管束鞘细胞中更多、更大的线粒体沿着靠近维管束的壁分布。松叶猪毛菜的CO2补偿点为30.4μmol mol-1，表明它具有较低程度的光合呼吸。松叶猪毛菜类似于C3植物的δ13C值(-22.4‰)，低的PEPC酶活性(61.5μmol mg-1chlorophyll-1h-1)和P-GDC酶专一的在维管束鞘细胞中表达，表明松叶猪毛菜属于type I C3-C4中间型植物。与藜科猪毛菜族已经报道的C3-C4中间型植物相比，虽然具有不同的叶片结构，但是它们却具有相近生理生化特性。

原文链接：

Salsola laricifolia, another C3-C 4 intermediate species in tribe Salsoleae s.l. (ChenopodiAceae) doi: 10.1007/s11120-014-0037-1.

This study identifies Salsola laricifolia as a C3-C4 intermediate in tribe Salsoleae s.l., Chenopodiaceae, and compares S. laricifolia with the previously described C3-C4 intermediates in Salsoleae. Photosynthetic pathway characteristics were studied in four species of this tribe including S. laricifolia, C3 Sympegma regelii, C3-C4 S. arbusculiformis, and C4 S. arbuscula, using the approaches of leaf anatomy and ultrastructure, activities of ribulose 1-5-bisphosphate carboxylase/oxygenase (Rubisco) and PEP carboxylase (PEPC), CO2 compensation point, and immunolocalization of Rubisco, PEPC, and the P-subunit of glycine decarboxylase (GDC). Salsola laricifolia has intermediate features, with near continuous and distinctive Kranz-like Cells (KLCs) compared with the C3-Sympegmoid anatomical type and the C3-C4 intermediate S. arbusculiformis, a relatively low CO2 compensation point (30.4 μmol mol(-1)) and mesophyll (M)-to KLC tissue ratio, mitochondria in KLCs primarily occurring along the centripetal wall, and specific localization of P-protein GDC in the KLCs. The C3-type isotope value (-22.4 ‰), the absence of the clear labeling for PEPC in M cells, and the low activity of the PEPC enzyme (61.5 μmol mg(-1 )chlorophyll(-1) h(-1)) support the identification of S. laricifolia as a type I C3-C4 intermediate. Although these C3-C4 intermediate species have different structural features, one with discontinuous KL cells and the other with continuous, they have similar characteristics in physiology and biochemistry.

作者：新疆生态与地理研