Changes in moisture content during wheat maturation -: what is measured by near infrared spectroscopy?

The aim of the present study was to detect maturation processes in wheat seed non-destructively with special respect to changes in moisture content and natural hydration/dehydration processes. Maturation is a phase of seed development in which a series of biochemical, enzymatic and morphological changes occur under highly hydrated conditions. The role of water is therefore critical to the whole maturation process. The amount and variation in content of different water species [high density water (HDW) with weaker hydrogen bonding and low density water (LDW) with stronger hydrogen bonding] changed considerably during maturation. Characteristic changes in three water absorption bands [1890-1920 nm (water I), 1400-1420 nm (water II) and 1150-1165 nm (water III)] were analysed. It was concluded that the different transitions of water molecules could be followed sensitively through different regions of NIR spectra. In the maturing seed, combination bands (water I and water III) were more sensitive indicators of changes in water molecules than was the first overtone (water II). The polar qualification system (PQS) provided sensitive and informative results regarding the amount and species of water in the developing seed. NIR spectroscopic techniques can be used effectively in monitoring plant physiological processes and the spectra have hidden information for predicting the stage of growth in wheat seed.