Abstract:Gas exchange and photosynthesis nutrient use efficiency were studied in leaves of Panicum miliaceum grown in heterogeneous (patchy) nutrient environments (HNEs). HNEs had a significant influence on gas exchange in the leaves of this species, but this effect varied among growth stages. In pre-reproductive stage individuals, photosynthetic rate (Pn), transpiration rate (E), and stomatal conductance (gs) decreased with increasing total nutrient availability in HNEs, while water use efficiency increased. These trends were reversed in the seed maturation stage. There was a significant correlation between gas exchange (Pn, E, gs) and leaf nitrogen (N). However, no such correlation was found between gas exchange and leaf phosphorus (P) or leaf potassium (K). Both P and K use efficiency were significantly affected by HNEs, but photosynthetic N use efficiency was not.