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On imbibition the seeds of certain species form a polysaccharide hydrogel, termed mucilage. In Arabidopsis thaliana and Camelina Sativa, this mucilage is composed of 2 layers, the outer being water-soluble while the inner is tightly attached to the seed surface. Determining the macromolecular properties of mucilage polymers in the inner mucilage layer can only be achieved in situ as detaching the polysaccharides involves breaking them either by physical or enzymatic methods, which alters or eliminates their structure. The physicochemical properties of mucilage polysaccharides will affect accessibility and mobility of molecules within the hydrogel. In order to compare inner mucilage properties between species, we have developed methods that can be applied to intact seeds. In a previous study we used low-field nuclear magnetic resonance (NMR) spectroscopy to characterize water uptake and mobility in Arabidopsis mucilage based on T2 relaxation times (Saez-Aguayo et al. 2014). We have now developed complementary cytological techniques to examine the molecule mobility that exploit fluorescent recovery after photobleaching (FRAP) and fluorescence anisotropy. Our results show that although molecules of different sizes show similar mobile fractions, the recovery time becomes slower with increased molecule size. The speed with which molecules rotate is also size dependent. The larger mucilage layer in Camelina sativa allowed mobility to be measured in different regions of the mucilage and indicate that heterogeneity for physicochemical properties exists within this layer. A comparison of mobility in Arabidopsis thaliana and Camelina sativa mucilage will be presented in addition to data from H-NMR microspectroscopy which is also being developed for Camelina seeds.

This is an expanded version of the notes to a course taught by the first author at the 1995 Les Houches Summer School. Constraints on a tentative reconciliation of quantum theory and general relativity are reviewed. It is explained what supersymmetric quantum theory teaches us about differential topology and geometry. Non-commutative differential topology and geometry are developed in some detail. As an example, the non-commutative torus is studied. An introduction to string theory and $M$(atrix) models is provided, and it is outlined how tools of non-commutative geometry can be used to explore the geometry of string theory and conformal field theory., 143 pages, LaTeX file + 3 eps-figures