The Relation of Water Absorption by Wheat Seeds to Water Potential

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Abstract
The progress of water absorption by wheat grains was studied by supplying water in the vapour phase, at controlled potentials. At a potential of −250 metres of water, the curve for water uptake against time shows exponential approach to equilibrium moisture content. Living and dead seeds behave similarly until germination effects are apparent. Water uptake in the early stages is probably due to physical rather than physiological processes. When germination occurs, it causes an exponential increase in the rate of water uptake. At higher potentials, up to zero, the uptake curves for dead seeds depart from the simple exponential relationship; in addition to the exponential component, there is a component the rate of which increases with time to a constant rate. The first component may represent the physical process of imbibition by the starch, and the second the initiation and progress of starch hydrolysis. A parameter a of the formula derived for the curves is interpreted as representing the diffusivity of water vapour in the seed material, depending upon the physical properties and dimensions of the seed.

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