Light Compensation Points and Acclimatization of Four Tropical Foliage Plants1

Abstract

Abstract Whole plant net CO2 exchange, light compensation points, and acclimatization were determined for Philodendron scandens Subsp. oxycardium (Schott) Bunt, Epipremnum aureum (Linden & Andre) Bunt (Pothos), Brassaia actinophylla Endl. and Dracaena sanderana Sander before and after 4 and 15 week acclimatization periods at 27 μE m−2 sec−1 (400-700 nm), for 12 hr/day. Philodendron scandens Subsp. oxycardium, E. aureum, B. actinophylla and D. Sanderana exhibited CO2 uptake rates of 0.53, 1.16, 1.18 and 0.50 mg CO2 dm−2hr−1, respectively, at 57 μE m−2 sec−l (3400 lx) after 15 weeks of acclimatization. Each species showed a significant increase in net CO2 uptake during the study period. Dark respiration decreased 63% in P. scandens Subsp. oxycardium, 71% in E. aureum, 53% in B. actinophylla and 64% in D. sanderana during the acclimatization period. The regression correlation coefficient of CO2 uptake with light intensity increased for each species during the study. At 15 weeks, P. scandens Subsp. oxycardium, E. aureum, B. actinophylla and D. sanderana exhibited r values of .95, .98, .96, and .91, respectively. Light compensation points decreased between week 1 and week 15 as follows: 33 to 7 μE m−2 sec−1 in P. scandens Subsp. oxycardium, 38 to 6 μE m−2 sec−1 in E. aureum, 14 to 4 μE m−2 sec−1 in B. actinophylla and 119 to 15 μE m−2 sec−1 in D. sanderana. As a result of acclimatization, all species exhibited increases in net CO2 uptake and decreases in dark CO2 evolution concomitantly indicating a reduction in dark respiration. Leaf area increase was negatively correlated with light compensation point. B. actinophylla had the highest leaf area increase with 2.16 dm2, E. aureum and P. scandens Subsp. oxycardium were intermediate with 1.08 and 0.96 dm2, respectively, while D. sanderana, the species with the highest light compensation point exhibited the lowest leaf area increase (0.44 dm2). Philodendron scandens Subsp. oxycardium, E. aureum, B. actinophylla, exhibited similarly rapid rates of acclimatization, while D. sanderana acclimatized much more slowly and had a significantly higher light compensation point.