Crop Science Laboratory, Faculty of Agriculture, Iwate University, Iwate 020-8550, Japan.
National Institute of Crop Science, Ibaraki 305-8518, Japan.
Physiol Plant. 2019 Mar;165(3):451-463. doi: 10.1111/ppl.12767. Epub 2018 Aug 31.
We investigated the fate of carbon dioxide (CO ) absorbed by roots or internally produced by respiration using gas exchange and stable isotopic labeling. CO efflux from detached leaves supplied with bicarbonate/CO solutions was followed over six cycles. CO effluxes were detected when bicarbonate solution at high pH was used, corresponding to 71-85% of the expected efflux. No CO efflux was detected when CO solutions at low pH were used but CO efflux was subsequently detected as soon as bicarbonate solutions at high pH were supplied. By sealing the leaf and petiole in a plastic bag to reduce diffusion to the atmosphere, a small CO efflux signal (14-30% of the expected efflux) was detected suggesting that CO in the xylem stream can readily escape to the atmosphere before reaching the leaf. When the root-zones of intact plants were exposed to CO solutions, a significant efflux from leaf surface was observed (13% of the expected efflux). However, no signal was detected when roots were exposed to a high pH bicarbonate solution. Isotopic tracer experiments confirmed that CO supplied to the root-zone was transported through the plant and was readily lost to the atmosphere. However, little C moved to the shoot when roots were exposed to bicarbonate solutions at pH 8, suggesting that bicarbonate does not pass into the xylem.
我们使用气体交换和稳定同位素标记来研究二氧化碳（CO ）被根部吸收或内部呼吸产生的命运。我们对供应碳酸氢盐/CO 溶液的离体叶片进行了六轮 CO 逸出的追踪。当使用高 pH 的碳酸氢盐溶液时，会检测到 CO 逸出，对应的 CO 逸出量为预期值的 71-85%。当使用低 pH 的 CO 溶液时，没有检测到 CO 逸出，但一旦供应高 pH 的碳酸氢盐溶液，就会随后检测到 CO 逸出。通过将叶片和叶柄密封在塑料袋中以减少向大气的扩散，我们检测到一个较小的 CO 逸出信号（预期逸出量的 14-30%），这表明木质部流中的 CO 可以在到达叶片之前很容易地逸出到大气中。当完整植株的根部暴露于 CO 溶液中时，会从叶片表面观察到显著的 CO 逸出（预期逸出量的 13%）。然而，当根部暴露于高 pH 碳酸氢盐溶液时，没有检测到信号。同位素示踪实验证实，供给根部的 CO 通过植物运输，并很容易逸出到大气中。然而，当根部暴露于 pH 8 的碳酸氢盐溶液时，只有少量的 C 转移到地上部分，这表明碳酸氢盐不会进入木质部。
