Gas exchange and epidermal characteristics of Miscanthus populations in Taiwan varying with habitats and nitrogen application

Seventeen clones of C-4 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 (N-0, N-1, and N-2, respectively) per pot. All the measurements were done 10-12 d after N application. The relationships between net photosynthetic rate (P-N) and photon flux density (PFD) showed a saturated curve, with PFD saturation at about 1 000 mu mol m(-2) s(-1). The ranges of PFD saturated P-N (P-sat) for all the tested clones with N-0, N-1, and N-2 were 8-16, 11-18, and 12-21 pmol m(-2) s(-1), respectively. The clones from southern Taiwan, a tropical region, showed the highest P-sat, followed by the clones from northern Taiwan, a subtropical region, while those from mountainous area showed the lowest P-sat. 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 P-sat 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.