Lintilhac P M, Wei C, Tanguay J J, Outwater J O
Department of Botany and Agricultural Biochemistry, The University of Vermont, Burlington 05405, USA.
J Plant Growth Regul. 2000 Mar;19(1):90-7. doi: 10.1007/s003440000009.
In this article we describe a new method for the determination of turgor pressures in living plant cells. Based on the treatment of growing plant cells as thin-walled pressure vessels, we find that pressures can be accurately determined by observing and measuring the area of the contact patch formed when a spherical glass probe is lowered onto the cell surface with a known force. Within the limits we have described, we can show that the load (determined by precalibration of the device) divided by the projected area of the contact patch (determined by video microscopy) provides a direct, rapid, and accurate measure of the internal turgor pressure of the cell. We demonstrate, by parallel measurements with the pressure probe, that our method yields pressure data that are consistent with those from the pressure probe. Also, by incubating target tissues in stepped concentrations of mannitol to incrementally reduce the turgor pressure, we show that the pressures measured by tonometry accurately reflect the predicted changes from the osmotic potential of the bathing medium. The advantages of this new method over the pressure probe are considerable, however, in that we can move rapidly from cell to cell, taking measurements every 20 s. In addition, the nondestructive nature of the method means that we can return to the same cell repeatedly for periodic pressure measurements. The limitations of the method lie in the fact that it is suitable only for superficial cells that are directly accessible to the probe and to cells that are relatively thin walled and not heavily decorated with surface features. It is also not suitable for measuring pressures in flaccid cells.
在本文中，我们描述了一种测定活植物细胞膨压的新方法。基于将生长中的植物细胞视为薄壁压力容器的处理方式，我们发现，当用已知力将球形玻璃探针降落到细胞表面时，通过观察和测量形成的接触斑面积，就能准确测定压力。在我们所描述的范围内，我们可以证明，负载（由设备的预校准确定）除以接触斑的投影面积（由视频显微镜确定）可直接、快速且准确地测量细胞的内部膨压。我们通过与压力探针进行平行测量证明，我们的方法得出的压力数据与压力探针的数据一致。此外，通过将目标组织置于逐步增加浓度的甘露醇中以逐步降低膨压，我们表明，张力测定法测得的压力准确反映了由浴液渗透压预测的变化。然而，这种新方法相对于压力探针的优势相当显著，因为我们可以在细胞间快速移动，每20秒进行一次测量。此外，该方法的非破坏性意味着我们可以反复回到同一个细胞进行定期压力测量。该方法的局限性在于，它仅适用于探针可直接触及的表层细胞以及相对薄壁且表面特征不复杂的细胞。它也不适用于测量萎蔫细胞中的压力。
