Aims: There is still limited information about the dynamics of potassium (K) uptake and use over the growth cycle in cereals, but quantification of such relationships is necessary to model crop response to K and improve K fertiliser practice. This study examined the effects of varying K supply on K use efficiency, leaf gas exchange, root and shoot growth at successive stages of plant phenological development, and on seed yield in wheat (Triticum aestivum L.). Methods: The study was conducted with a low-K loamy sand in a naturally-lit glasshouse. Six rates of soil K were applied as 15, 22.5, 30, 45, 75, 135 mg K kg-1, and six harvests were made to assess growth responses at different stages. Results: Tiller development, shoot dry weight, leaf photosynthesis and transpiration efficiency were closely related to soil K supply with time. Plants with 15 to 45 mg K kg-1 had lower root-to-shoot ratio than those supplied with 75 or 135 mg K kg-1. Plants showed maximal K accumulation in shoots prior to anthesis regardless of K rates, but K use efficiency differed during growth among the treatments. Adequate K supply enhanced seed yield by increasing ear numbers, single seed weight and harvest index. Conclusions: The rates of K supply affect K use efficiency, the root-to-shoot ratio and seed yield in wheat with a key feature of growth on a low-K sand as active K uptake during vegetative growth and subsequent reliance on K redistribution for reproductive growth. The poor adaptation of root growth to K deficiency may impair the plant's ability for nutrient acquisition especially in water limited environment. © 2013 Springer Science+Business Media Dordrecht.