a b s t r a c t Superabsorbent hydrogels (SH) continue being a very important issue in both academic and industrial fields due to their applications in several technologies. This is proved by the impressive number of publications, through papers and patents as well, dealing with SH. This review is targeted to update and discuss some important aspects of synthesis, characterization and application of SH in agriculture, mainly those based on polysaccharides, as soil conditioners and as polymer carriers for nutrient release. Basic properties of SH and some methods for chemically modifying polysaccharides are given and some directions for hydrogels preparation are highlighted as well. Mechanisms associated with water transport into the 3D matrix, taking into account the transference of mass from hydrogelsoil system to plant, are discussed in the light of some mathematical models. Release of nutrients either from granules coated by hydrophilic polymer or from SH, targeting applications in agriculture, is also discussed on the basis of often used mathematical models (the swelling-based kinetic models) and on a diffusion-based kinetic model with a partition activity coefficient. Examples of recent applications in agriculture as soil conditioners and carriers for nutrient release (fertilizers, etc.) are given. At the final, future trends and perspectives are considered. More than two hundreds references are cited in the whole text.

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Transesterification and epoxide ring-opening reactions are two mechanism routes that explain chemical modifications of macromolecules by glycidyl methacrylate (GMA). Although the coupling reaction of the GMA with macromolecules has widely been investigated, there are still mechanisms that remain to be explained when GMA is processed in an aqueous solution at different pH conditions. To this end, reaction mechanisms of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAAc) by GMA in water in acidic and basic conditions were investigated thoroughly. The presence of hydroxyl groups in PVA and carboxyl groups in PAAc allowed for a better evaluation of the reaction mechanisms. The analysis of the (1)H and (13)C NMR spectra clearly demonstrated that the chemical reactions of GMA with carboxyl groups and alcohols of the macromolecules in an aqueous solution are dependent on pH conditions. At pH 3.5, the GMA reacts with both the carboxylic and the hydroxyl groups through an epoxide ring-opening mechanism. At pH 10.5, the GMA undergoes a hydrolysis process and reacts with hydroxyl groups by way of both the transesterification and the epoxide ring-opening mechanisms, whereas the ring-opening reaction is the preferential pathway.