Light Compensation Points and Acclimatization of Four Tropical Foliage Plants1

Abstract

Abstract Whole plant net CO 2 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 μ E m −2 sec −1 (400-700 nm), for 12 hr/day. Philodendron scandens Subsp. oxycardium, E. aureum, B. actinophylla and D. Sanderana exhibited CO 2 uptake rates of 0.53, 1.16, 1.18 and 0.50 mg CO 2 dm −2 hr −1 , respectively, at 57 μ E m −2 sec −l (3400 lx) after 15 weeks of acclimatization. Each species showed a significant increase in net CO 2 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 CO 2 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 μ E m −2 sec −1 in P . scandens Subsp. oxycardium , 38 to 6 μ E m −2 sec −1 in E. aureum , 14 to 4 μ E m −2 sec −1 in B. actinophylla and 119 to 15 μ E m −2 sec −1 in D. sanderana. As a result of acclimatization, all species exhibited increases in net CO 2 uptake and decreases in dark CO 2 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 dm 2 , E. aureum and P . scandens Subsp. oxycardium were intermediate with 1.08 and 0.96 dm 2 , respectively, while D. sanderana , the species with the highest light compensation point exhibited the lowest leaf area increase (0.44 dm 2 ). 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.