猪毛菜属3种不同光合型物种的生长适应特征比较

干旱是促进C₄光合途径进化的外部动力之一,探究干旱胁迫导致植物光合型向C₄发生适应性演化对荒漠化植被的保护和恢复意义重大。猪毛菜属是藜科包含不同光合型物种的属,是研究干旱驱动C₄进化的理想材料。当前支持植物C₄光合进化的解剖结构证据充分且深入,而关注C₄光合进化进程中生长适应特征的研究不多。为此,基于猪毛菜属内各个种的系统进化关系,以蒿叶猪毛菜(C₃型)、松叶猪毛菜(C₃-C₄型)和东方猪毛菜(C₄型)为试验材料,研究其在各自生境下的叶片形态解剖结构和种子形态特征、抗旱生理和生态化学计量特征,分析猪毛菜属不同光合型植物在干旱胁迫下的生长适应差异。结果表明:C₃型猪毛菜是原始祖先,C₃-C₄型猪毛菜与C₄型猪毛菜由C₃型猪毛菜进化而来;与C₃型蒿叶猪毛菜相比,C₃-C₄中间型松叶猪毛菜以及C₄型东方猪毛菜叶从外部形态和解剖结构上逐渐形成适应干旱的结构特征,且种子的传播策略也因种子大小不同而发生变化;C₄型猪毛菜因高光合能力使其具备通过可溶性糖来调节渗透能力的物质基础,从而提高抗旱能力;C₃-C₄型猪毛菜是通过提高氮和磷的利用效率来增加固碳量,C₄型猪毛菜是通过氮和磷含量的增多来增加固碳量。相较于C₃蒿叶猪毛菜,C₃-C₄松叶猪毛菜和C₄东方猪毛菜更能适应贫瘠的环境。以上试验结果可为完善C₄光合进化理论提供生理生态适应性证据。

Growth adaptation characteristics of three Salsola species with different photosynthetic systems

Drought is one of the external forces that has promoted the evolution of the C₄ photosynthetic pathway. It is great of significance to explore the photosynthetic evolution of the C₄ pathway under drought stress for the protection and restoration of vegetation in areas threatened by desertification. Because the Salsola genus contains different photosynthetic types, it is an ideal material to study C₄ evolution driven by drought. Most previous studies on the photosynthetic evolution of plants have focused on changes at the anatomical level, rather than on the characteristics of growth adaptation. On the basis of the phylogenetic relationships of various species in the Salsola genus, we chose Salsola abrotanoides (C₃), Salsola laricifolia (C₃-C₄) and Salsola orientalis (C₄) as the experimental materials. We analyzed growth adaptation characteristics such as leaf morphology and anatomy, seed morphology, resistance physiological indicators, and ecological chemometric indexes. The results showed that the C₃-photosynthetic type in the Salsola genus is the original ancestor, and that the C₃-C₄ photosynthetic type and the C₄ photosynthetic type have evolved from the C₃ photosynthetic type. Compared with the C₃ species S. abrotanoides, the C₃-C₄ species S. laricifolia and the C₄ species S. orientalis have gradually adapted to drought by changing their external morphology and anatomical structure, and by adjusting their seed propagation strategies by forming differently sized seeds. The high photosynthetic capacity of C₄ plants provides materials (soluble sugars) involved in regulation, and with the evolution to C₄ photosynthesis, the drought resistance capacity of the Salsola genus has been enhanced. To increase the amount of carbon fixed by photosynthesis, S. laricifolia has increased its nitrogen and phosphorus use efficiencies, while S. orientalis has increased its nitrogen and phosphorus contents. Compared with S. abrotanoides, S. laricifolia and S. orientalis are more adapted to barren environments. These experimental data provide evidence of the physio-ecological adaptations that have improved C₄ photosynthesis, consistent with evolutionary theory.