Messerli Mark A, Smith Peter J S, Lewis Robert C, Robinson Kenneth R
BioCurrents Research Center, Program in Molecular Physiology, Marine Biological Laboratory, Woods Hole, MA 02543, USA.
Plant J. 2004 Dec;40(5):799-812. doi: 10.1111/j.1365-313X.2004.02252.x.
Microelectrodes, made from a Cl(-)-selective liquid ion exchanger previously used to measure putative Cl- fluxes in Lilium longiflorum pollen tubes, were characterized. The electrodes were poorly selective, possessing only about 10-fold selectivity for Cl- over other anions tested. They had only 2.4-fold selectivity for Cl- over the anionic form of the H+ buffer, MES, indicating that the electrode can indirectly detect H+ gradients. Apparent anion influx was detected along the pollen tube shafts and at the grains while apparent anion efflux was detected near the tip of the tube. During oscillating growth, the peak of the oscillating apparent anion efflux at the tip occurred, on average, 7.9 sec after the peak of the growth oscillations. Consideration of the previously characterized H+ fluxes in lily pollen grains and tubes, as well as the poor anion selectivity of the Cl- electrodes, indicates that the putative Cl- fluxes are in fact changes in the anionic concentration of the buffer resulting from H+ gradients and not changes in Cl- concentration. The claim of a central role for Cl- in lily pollen tube growth is further undermined by the fact that these tubes grow at the same rate if the Cl- content of the growth medium is reduced to trace levels (< or =31 microM), and that the grains have only small reserves of Cl-. These results lead to the conclusion that Cl- fluxes are not a significant component of pollen tube growth and Cl- itself is not required for growth.
对由一种氯离子选择性液体离子交换剂制成的微电极进行了表征，该离子交换剂先前用于测量麝香百合花粉管中假定的氯离子通量。这些电极选择性较差，对氯离子的选择性仅比对其他测试阴离子高约10倍。它们对氯离子的选择性仅比对氢离子缓冲剂MES的阴离子形式高2.4倍，这表明该电极可以间接检测氢离子梯度。在花粉管轴和花粉粒处检测到明显的阴离子内流，而在花粉管尖端附近检测到明显的阴离子外流。在振荡生长过程中，花粉管尖端振荡明显阴离子外流的峰值平均在生长振荡峰值后7.9秒出现。考虑到先前表征的百合花粉粒和花粉管中的氢离子通量，以及氯离子电极较差的阴离子选择性，表明假定的氯离子通量实际上是由氢离子梯度导致的缓冲剂阴离子浓度变化，而不是氯离子浓度变化。生长培养基中氯离子含量降低到痕量水平（≤31微摩尔）时，这些花粉管仍以相同速率生长，且花粉粒中氯离子储备很少，这一事实进一步削弱了氯离子在百合花粉管生长中起核心作用的说法。这些结果得出结论：氯离子通量不是花粉管生长的重要组成部分，生长本身不需要氯离子。
