Division of Civil Engineering, University of Dundee, UK.
Ann Bot. 2012 Feb;109(2):419-27. doi: 10.1093/aob/mcr296. Epub 2011 Nov 23.
Myxospermy is a term which describes the ability of a seed to produce mucilage upon hydration. The mucilage is mainly comprised of plant cell-wall polysaccharides which are deposited during development of those cells that comprise the seed coat (testa). Myxospermy is more prevalent among those plant species adapted to surviving on arid sandy soils, though its significance in determining the ecological fitness of plants is unclear. In this study, the first mathematical model of myxospermous seed mucilage expansion is presented based on seeds of the model plant species Capsella bursa-pastoris (shepherd's purse).
The structures underpinning the expansion process were described using light, electron and time-lapse confocal micrographs. The data and experimental observations were used to create a mathematical model of myxospermous seed mucilage expansion based on diffusion equations.
The mucilage expansion was rapid, taking 5 s, during which the cell mucilage volume increased 75-fold. At the level of the seed, this represented a 6-fold increase in seed volume and a 2·5-fold increase in seed surface area. These increases were shown to be a function of water uptake (16 g water g(-1) mucilage dry weight), and relaxation of the polymers which comprised the mucilage. In addition, the osmotic pressure of the seed mucilage, estimated by assessing the mucilage expansion of seeds hydrated in solutions of varying osmotic pressure, was -0·54 MPa (equivalent to 0·11 M or 6·6 g L(-1) NaCl).
The results showed that the mucilage may be characterized as hydrogel and seed-mucilage expansion may be modelled using the diffusion equation described. The potential of myxospermous seeds to affect the ecological services provided by soil is discussed briefly.
黏液性种子是指种子在遇水时产生黏液的能力。黏液主要由植物细胞壁多糖组成，这些多糖是在构成种皮（种壳）的细胞发育过程中沉积的。黏液性种子在适应干旱沙质土壤的植物物种中更为普遍，尽管其在决定植物生态适应性方面的意义尚不清楚。在这项研究中，首次提出了基于模式植物荠（Capsella bursa-pastoris）种子的黏液性种子黏液膨胀的第一个数学模型。
使用光、电子和延时共聚焦显微镜照片描述了膨胀过程的结构。利用数据和实验观察结果，基于扩散方程，创建了黏液性种子黏液膨胀的数学模型。
黏液膨胀迅速，仅需 5 秒，在此期间细胞黏液体积增加了 75 倍。在种子水平上，这代表种子体积增加了 6 倍，种子表面积增加了 2.5 倍。这些增加被证明是水分吸收（16 g 水 g(-1) 黏液干重）和构成黏液的聚合物松弛的函数。此外，通过评估在不同渗透压溶液中膨胀的种子的黏液渗透压，估计了种子黏液的渗透压为-0.54 MPa（相当于 0.11 M 或 6.6 g L(-1) NaCl）。
结果表明，黏液可被视为水凝胶，可使用所描述的扩散方程对种子黏液膨胀进行建模。简要讨论了黏液性种子对土壤提供的生态服务的潜在影响。
