Photosynthetic Response of Selected Red Maple Cultivars to Light

Abstract

Four red maple {Acer rubrum L.) cultivars ('FranksrecT - Red Sunset™, 'Northwood', 'October Glory', and 'Schlesingeri') grown in containers were evaluated for response to different photosynthetically active radiation (PAR) levels. As PAR increased, there was a linear increase in net photosynthesis (Pn) and transpiration (E) for 'Franksred' and 'October Glory'. In contrast, Pn and E for 'Northwood' and 'Schlesingeri' increased as PAR increased to about 1375 |imol-m'2-s'1 and 1350 u.mol-m~2-s\ respectively and declined thereafter. PAR had no relationship to water use efficiency (calculated as Pn/E) for the four cultivars. Mesophyll resistance ( r j to CO2 (Cl/Pn) decreased linearly as PAR increased for 'October Glory'; but'Franksred', 'Northwood', and 'Schlesingeri' exhibited a quadratic response to PAR (with estimated lows of 17.61 cm-sec1 at 1600 PAR, and 16.45 cm-sec1 and 16.36 cm-sec1 at 1400 PAR, respectively). The enhanced photosynthetic mechanism for rm as PAR levels increased suggests that 'October Glory' is the most adapted cultivar of the four selections in this study for high PAR environments. Furthermore, adaptive ranges of red maple cultivars may be predicted during developmental stages by establishing light curves for Pn, E, and r.