GENOTYPIC VARIATION IN LIGHT-RESPONSE AND TEMPERATURE-RESPONSE OF PHOTOSYNTHESIS IN NOTHOFAGUS-SOLANDRI VAR CLIFFORTIOIDES AND NOTHOFAGUS-MENZIESII

Responses of photosynthesis to light and temperature were studied in t wo Nothofagus species native to New Zealand: N. solandri var. cliffort ioides (Hook. f.) Poole and N. menziesii (Hook. f.) Oerst.. Measuremen ts of leaf photosynthesis were made in a controlled environment growth chamber at photosynthetic photon flux density between 0 and 700 mu mo l m(-2) sl with temperatures set for 10, 20 and 25 degrees C, on seedl ings previously grown in a glasshouse from seed of three different ori gins. In both species, pronounced intraspecific variation was shown in dark respiration, light compensation point and light-saturated net ph otosynthesis (A(max)). Seedlings of N. solandri showed higher dark res piration and light compensation levels than N. menziesii seedlings, bu t the two species did not differ in A(max). Change in temperature resu lted in significant change in the response of photosynthesis to light in both N. solandri and N. menziesii. The differences between N. solan dri and N. menziesii in light response of photosynthesis are discussed in terms of ecosystem dynamics of Nothofagus forests in New Zealand.