The Macaulay Institute for Soil Research, Craigiebuckler, AB9 2 QJ, Aberdeen, U.K..
Planta. 1975 Jan;122(2):131-41. doi: 10.1007/BF00388653.
From compartmental analysis of radioisotope elution measurements, concentrations and fluxes of Ca(2+) were estimated for cortical cells in root segments of onion, Allium cepa L., relative to a complete nutrient solution containing 1 mM Ca(2+). Five compartments for Ca(2+) in the cortex were revealed. These were identified, in order of increasing rates of exchange, with the vacuole and cytoplasm of the cortical parenchyma, the Donnan free space in the cell walls, the water free space in the tissue and the superficial film of solution on the segments. With the Ussing-Teorell flux ratio equation as the criterion, it was concluded that Ca(2+) entered the cytoplasm passively and was actively pumped back to the external solution. Ca(2+) concentration in the vacuole could only be estimated as lying between wide limits (1.0 to 7.5 μeq. ml(-1)), but even at the maximum concentration, it was concluded that entry was passive and content limited by an efflux pump across the tonoplast. Net flux was zero and the vacuolar concentration of Ca(2+) compatible with this was found to be 2.6 μeq. ml(-1). The transported fraction of the total efflux, appearing at the segment cut ends, was estimated separately. Calcium was found to be transported almost exclusively in the basipetal direction.
从放射性同位素洗脱测量的隔室分析中，相对于含有 1mM Ca2+的完整营养溶液，估计了洋葱（Allium cepa L.）根段皮层细胞中 Ca2+的浓度和通量。揭示了皮层中有 5 个 Ca2+隔室。这些隔室按交换速率的顺序依次被鉴定为：皮层薄壁细胞质和液泡、细胞壁中的 Donnan 自由空间、组织中的水自由空间和段上溶液的表面膜。根据 Ussing-Teorell 通量比方程作为标准，得出结论，Ca2+被动进入细胞质并被主动泵回外溶液。液泡中 Ca2+的浓度只能估计为在宽范围（1.0 到 7.5 μeq. ml-1）之间，但即使在最大浓度下，也得出结论，进入是被动的，并且通过液泡膜上的外排泵限制了内容物。净通量为零，与该净通量兼容的液泡中 Ca2+浓度被发现为 2.6 μeq. ml-1。分别估计了在段切端出现的总外排的转运部分。发现 Ca2+几乎完全沿基底方向运输。
