Plant tissues exhibit a symplasmic organization; the individual protoplasts are connected to their neighbors via cytoplasmic bridges that extend through pores in the cell walls. These bridges may have diameters of a micrometer or more, as in the sieve pores of the phloem, but in most cell types they are smaller. Historically, botanists referred to cytoplasmic bridges of all sizes as plasmodesmata. The meaning of the term began to shift when the transmission electron microscope (TEM) became the preferred tool for studying these structures. Today, a plasmodesma is widely understood to be a 'nano-scale' pore. Unfortunately, our understanding of these nanoscopic channels suffers from methodological limitations. This is exemplified by the fact that state-of-the-art EM techniques appear to reveal plasmodesmal pore structures that are much smaller than the tracer molecules known to diffuse through these pores. In general, transport processes in pores that have dimensions in the size range of the transported molecules are governed by different physical parameters than transport process in the macroscopic realm. This can lead to unexpected effects, as experience in nanofluidic technologies demonstrates. Our discussion of problems of size in plasmodesma research leads us to conclude that the field will benefit from technomimetic reasoning - the utilization of concepts developed in applied nanofluidics for the interpretation of biological systems.

中文翻译：

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Plasmodesmata 和大小问题：解释混淆

植物组织表现出共质组织；单个原生质体通过延伸穿过细胞壁孔的细胞质桥与其相邻的原生质体相连。这些桥可能具有一微米或更大的直径，如韧皮部的筛孔，但在大多数细胞类型中它们更小。历史上，植物学家将各种大小的细胞质桥称为胞间连丝。当透射电子显微镜 (TEM) 成为研究这些结构的首选工具时，该术语的含义开始发生变化。今天，胞间连丝被广泛理解为“纳米级”孔隙。不幸的是，我们对这些纳米通道的理解受到方法学上的限制。最先进的 EM 技术似乎揭示了比已知通过这些孔扩散的示踪分子小得多的等离子孔结构。一般来说，尺寸在被传输分子大小范围内的孔中的传输过程与宏观领域中的传输过程受不同的物理参数控制。正如纳米流体技术的经验所证明的那样，这可能会导致意想不到的效果。我们对胞间连丝研究中大小问题的讨论使我们得出结论，该领域将受益于技术模拟推理——利用应用纳米流体学中开发的概念来解释生物系统。尺寸在被传输分子大小范围内的孔中的传输过程与宏观领域中的传输过程受不同的物理参数控制。正如纳米流体技术的经验所证明的那样，这可能会导致意想不到的效果。我们对胞间连丝研究中大小问题的讨论使我们得出结论，该领域将受益于技术模拟推理——利用应用纳米流体学中开发的概念来解释生物系统。尺寸在被传输分子大小范围内的孔中的传输过程与宏观领域中的传输过程受不同的物理参数控制。正如纳米流体技术的经验所证明的那样，这可能会导致意想不到的效果。我们对胞间连丝研究中大小问题的讨论使我们得出结论，该领域将受益于技术模拟推理——利用应用纳米流体学中开发的概念来解释生物系统。