| Abstract: | The progress of water absorption by wheat grains was studiedby supplying water in the vapour phase, at controlled potentials. At a potential of –250 metres of water, the curve forwater uptake against time shows exponential approach to equilibriummoisture content. Living and dead seeds behave similarly untilgermination effects are apparent. Water uptake in the earlystages is probably due to physical rather than physiologicalprocesses. When germination occurs, it causes an exponentialincrease in the rate of water uptake. At higher potentials, up to zero, the uptake curves for deadseeds depart from the simple exponential relationship; in additionto the exponential component, there is a component the rateof which increases with time to a constant rate. The first componentmay 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 interpretedas representing the diffusivity of water vapour in the seedmaterial, depending upon the physical properties and dimensionsof the seed. |
