Deng Wenni, Iannetta Pietro P M, Hallett Paul D, Toorop Peter E, Squire Geoffrey R, Jeng Dong-Sheng
Division of Civil Engineering, University of Dundee, Dundee, UK.
Biorheology. 2013;50(1-2):57-67. doi: 10.3233/BIR-130627.
The outer surface of myxospermous seed coats contains mucilage which absorbs large amounts of water relative to its dry weight. Ecologically, the seed mucilage can affect seed germination and dormancy. Upon hydration, a large proportion of the seed mucilage is lost to the soil and the physics of soil-seed mucilage interactions has not been assessed. Towards that end, the dynamic rheological properties of mucilage extracted from Capsella bursa-pastoris L. Medik. (shepherd's purse) seeds were assessed as a function of mucilage concentration (1-10% [w/w]), temperature (0-80°C) and shear frequency (0.1-100 rad s-1). The seed mucilage was shear thinning and was classified as a highly viscous "weak gel". The relationship between the viscoelastic parameters (viscosity, η*, storage and loss modulus, G' and G″, yield and flow stresses, τy and τf) and mucilage concentration were well fitted by power law models. The values of η*, G' and G″ increased as temperature increased above 40°C and were also slightly frequency dependent. The shepherd's purse seed mucilage is more viscous than that from other plant parts, such as fruits and roots. These properties highlight the possibility that seed mucilage may affect soil conditions and therefore present an additional facilitative ecological role (beyond that already reported, which directly affect seed biology); and this is discussed.
粘液质种皮的外表面含有粘液，相对于其干重，这种粘液能吸收大量水分。从生态学角度来看，种子粘液会影响种子的萌发和休眠。在水合作用下，大部分种子粘液会流失到土壤中，而土壤与种子粘液相互作用的物理学机制尚未得到评估。为此，对从荠菜种子中提取的粘液的动态流变特性进行了评估，评估内容包括粘液浓度（1-10%[w/w]）、温度（0-80°C）和剪切频率（0.1-100 rad s-1）的函数关系。种子粘液表现出剪切变稀特性，被归类为高粘性的“弱凝胶”。幂律模型很好地拟合了粘弹性参数（粘度η*、储能模量和损耗模量G'和G″、屈服应力和流动应力τy和τf）与粘液浓度之间的关系。当温度高于40°C时，η*、G'和G″的值会增加，并且也略微依赖于频率。荠菜种子粘液比其他植物部位（如果实和根）的粘液更粘稠。这些特性凸显了种子粘液可能影响土壤条件的可能性，因此呈现出一种额外的促进生态作用（除了已经报道的直接影响种子生物学的作用之外）；对此进行了讨论。
