Institut für Forstbotanik und Baumphysiologie, Professur für Baumphysiologie, Albert-Ludwigs-Universität Freiburg, Georges-Koehler-Allee 053/054, 79110 Freiburg, Germany.
Tree Physiol. 2010 Sep;30(9):1161-73. doi: 10.1093/treephys/tpq041. Epub 2010 Jun 1.
The poplar hybrid Populus x canescens (syn. Populus tremula x Populus alba) was subjected to salt stress by applying 75 mM NaCl for 2 weeks in hydroponic cultures. Decreasing maximum quantum yield (Fv/Fm) indicated damage of photosystem II (PS II), which was more pronounced under nitrate compared with ammonium nutrition. In vivo staining with diaminobenzidine showed no accumulation of H(2)O(2) in the leaf lamina; moreover, staining intensity even decreased. But at the leaf margins, development of necrotic tissue was associated with a strong accumulation of H(2)O(2). Glutathione (GSH) contents increased in response to NaCl stress in leaves but not in roots, the primary site of salt exposure. The increasing leaf GSH concentrations correlated with stress-induced decreases in transpiration and net CO(2) assimilation rates at light saturation. Enhanced rates of photorespiration could also be involved in preventing reactive oxygen species formation in chloroplasts and, thus, in protecting PS II from damage. Accumulation of Gly and Ser in leaves indeed indicates increasing rates of photorespiration. Since Ser and Gly are both immediate precursors of GSH that can limit GSH synthesis, it is concluded that the salt-induced accumulation of leaf GSH results from enhanced photorespiration and is thus probably restricted to the cytosol.
杂交杨（Populus x canescens，又名 Populus tremula x Populus alba）在水培条件下经 75mM NaCl 处理 2 周以模拟盐胁迫。最大光化学量子产量（Fv/Fm）的降低表明 PS II 受到了损伤，而硝态氮营养比铵态氮营养对 PS II 的损伤更为明显。活体二氨基联苯（DAB）染色表明叶片中并未积累 H2O2；相反，染色强度甚至降低。但在叶片边缘，坏死组织的发育与 H2O2的大量积累有关。谷胱甘肽（GSH）含量在叶片中随着 NaCl 胁迫的增加而增加，但在根中（盐暴露的主要部位）则没有增加。叶片中 GSH 浓度的增加与胁迫诱导的饱和光下蒸腾作用和净 CO2 同化速率的降低有关。增强的光呼吸速率也可能参与到防止叶绿体中活性氧的形成，从而保护 PS II 免受损伤。叶片中 Gly 和 Ser 的积累确实表明光呼吸速率的增加。由于 Ser 和 Gly 都是 GSH 的直接前体，可能会限制 GSH 的合成，因此可以得出结论，盐诱导的叶片 GSH 积累是由于增强的光呼吸作用所致，因此可能仅限于细胞质。
