**Abstract**

Pakistan's agriculture sector faces a 50% water shortage, impacting crops like cotton and the textile industry, thus affecting the economy. K-efficient cotton cultivars, which withstand dry conditions through morphological and biochemical traits, can conserve moisture. K-efficient cotton cultivars can be used as donors of key K acquisition traits in breeding programs to develop promising cotton varieties with enhanced yields for the low K environments and can also be recommended for general cultivation to improve cotton production on a sustainable basis. This chapter aims to contribute to enhance water use efficiency (WUE) on the physiological basis to develop strategies for K-efficient cotton cultivars for improvement. Strategies involve regulating transcription factors to improve K-uptake efficiency, increasing root volume through lateral roots and root hairs, and enhancing K-uptake via channels and transporters, ultimately boosting WUE. Molecular breeding programs can leverage K+-associated QTLs to develop high K+ use efficiency cultivars. Physiological processes affecting WUE are discussed alongside factors influencing their contributions, acknowledging the complexity across crops, environments, and nutrients.

**Keywords:** K-efficient cultivars, gas exchange traits, morphological traits, water use efficiency, potassium use efficiency
