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Water availability and water management have been critical to the ecology of prehistoric agriculture. Grasses (Gramineac) in general and cereals in particular are among the plants with the highest deposition of opal silica both inside the cells and also in the intercellular space (as discrete bodies called phytoliths). This study attempts to establish a correlation between biogenic opal silica from cereals and the plant-water conditions under which it has formed. A two-step experimental process was developed to check phytolith production (fixed and sensitive forms) under different conditions of water availability and to understand water binding in the opal silica reticule. The first results presented from this study show that there is some variability in phytolith production according to the water regime under which the plant grew and sensitive forms show to be directly influenced by the water regime at least in bread wheat (Triticum aestivian), emmer wheat (Triticum dicoccum) and 2-row barley (Hordeum distichon). Also, phytolith X-ray analysis of T aestivum shows that chemical bounding of water molecules in the biogenic opal matrix of the sensitive forms is associated with water availability during the plant growth. (C) 2007 Elsevier Ltd and INQUA. All rights reserved.