Seventeen clones of C4 grass Miscanthus spp. collected from different climatic regions and elevations of Taiwan were transplanted in pots. 15-16 months after collection the plants received 0, 1, and 2 g of nitrogen fertiliser (N0, N1, and N2, respectively) per pot. All the measurements were done 10-12 d after N application. The relationships between net photosynthetic rate (PN) and photon flux density (PFD) showed a saturated curve, with PFD saturation at about 1 000 µmol m-2 s-1. The ranges of PFD saturated PN (Psat) for all the tested clones with N0, N1, and N2 were 8-16, 11-18, and 12-21 µmol m-2 s-1, respectively. The clones from southern Taiwan, a tropical region, showed the highest Psat, followed by the clones from northern Taiwan, a subtropical region, while those from mountainous area showed the lowest Psat. The clones collected from southern Taiwan showed the highest frequency of stomata on the adaxial surface, and those collected from the high mountainous area showed the lowest frequency. Also the adaxial surface of leaves from the higher mountainous area had more wax deposited than the leaves from the lowland. Thus the low Psat in mountain clones is limited by both stomatal and non-stomatal factors. Further, the lower leaf conductance and different epidermal characteristics of mountain clones might prevent excessive loss of heat through transpiration and provide production against ultraviolet-B radiation. and J. H. Weng, F. H. Hsu.