E were ten replicate pots per nitrogen x competition combination, five of which were grown in a shadehouse, and five of which were grown in full sunlight. The two light levels were analyzed as separate experiments (a). The photograph shows a sun-grown (left) and shade-grown plant (right) side by side (b). doi:10.1371/journal.pone.0047554.gdetected, so it is very unlikely that induction of defenses affected the data. Results indicate the competition treatment increased available nitrogen rather than decreasing it (because P. macroloba has N-fixing root nodules), and other work shows legumes can enhance the performance of neighboring MNS custom synthesis plants [60].Seedling MeasurementsSeedling height (cm), leaf area (cm2), the light saturated rate of photosynthesis (Amax; mmol CO2/m2/s), and dark respiration (mmol CO2/m2/s) were measured for each replicate after six months of growth. Leaf samples were also collected at this time for chemistry analyses. The area of all the leaves on each seedling was measured as the length and width of the leaves multiplied together (cm2); the leaves are bipinnately compound, so this measurement was used to compare leaf sizes but not to determine actual leaf area. For pots with competition, the average height and leaf area of individuals in the same pot were used in analyses. Plant biomass was determined using regression equations from field collected seedlings (sun n = 10; shade n = 14). PAR at the seedlings was measured between 11:00 and 13:00, and the shade collected plants had an average PAR of 20 while the sun collected plants had anaverage PAR of 84 . The height and leaf area of the collected seedlings was measured, and the stems and leaves of the seedlings were then oven dried at 40 degrees Celsius for 72 hours and weighed. Regressions of aboveground biomass by stem height plus leaf area were then created (sun plants R2 = 0.76, P = 0.001; shade plants R2 = 0.55, P = 0.002). The resulting regression formulas were used to calculate aboveground biomass for the experimental seedlings. Amax and dark respiration were measured with a LI-COR 6400 gas exchange system (LI-COR, Nebraska, USA), and only one individual was measured in pots with competition. The third leaf from the apical meristem was measured for consistency in leaf age. Measurements were made between 7:00 and 13:00 hours. Leaves were clamped into an airtight cuvette with 
a red-blue LED light source. Incoming CO2 was set to 380 mmol/mol from a CO2 
cartridge. Light response curves were made from darkness to 10, 25, 50, 100, 150, 200 mmol/s and continued in increments of 200 mmol/s until an asymptote was reached. Leaves were given 120 seconds to adjust to each light level, and the CO2 differential was recorded when flow rate, CO2 and humidity were constant. The flow rate was set to 550 mmol/s, and humidity was betweenVariation in Costs of Terpenoids and PhenolicsTable 1. MANOVA and profile analysis results for the response of Pentaclethra macroloba photosynthesis, biomass, and carbon-based metabolites (sugars, flavans, and saponins) to light, fertilizer, and competition.Photosynthesis and biomass Pluripotin biological activity Factor df MANOVA FPProfile F PSun plants Fertilizer Competition 2 1 0.2 0.05 0.8 0.8 2.4 2.8 0.1 0.Error Shade plants Fertilizer Competition20.97 8.0.4 0.0.8 0.0.5 0.Error Metabolites Factor Sun plants Fertilizer CompetitiondfMANOVA FPProfile F P20.2 19.0.8 0.0.2 19.0.8 0.Error Shade plants Fertilizer Competition Fert. * comp. Error2 1 20.8 0.2 5.0.5 0.6 0.1.1 0.03 0.0.4 0.E were ten replicate pots per nitrogen x competition combination, five of which were grown in a shadehouse, and five of which were grown in full sunlight. The two light levels were analyzed as separate experiments (a). The photograph shows a sun-grown (left) and shade-grown plant (right) side by side (b). doi:10.1371/journal.pone.0047554.gdetected, so it is very unlikely that induction of defenses affected the data. Results indicate the competition treatment increased available nitrogen rather than decreasing it (because P. macroloba has N-fixing root nodules), and other work shows legumes can enhance the performance of neighboring plants [60].Seedling MeasurementsSeedling height (cm), leaf area (cm2), the light saturated rate of photosynthesis (Amax; mmol CO2/m2/s), and dark respiration (mmol CO2/m2/s) were measured for each replicate after six months of growth. Leaf samples were also collected at this time for chemistry analyses. The area of all the leaves on each seedling was measured as the length and width of the leaves multiplied together (cm2); the leaves are bipinnately compound, so this measurement was used to compare leaf sizes but not to determine actual leaf area. For pots with competition, the average height and leaf area of individuals in the same pot were used in analyses. Plant biomass was determined using regression equations from field collected seedlings (sun n = 10; shade n = 14). PAR at the seedlings was measured between 11:00 and 13:00, and the shade collected plants had an average PAR of 20 while the sun collected plants had anaverage PAR of 84 . The height and leaf area of the collected seedlings was measured, and the stems and leaves of the seedlings were then oven dried at 40 degrees Celsius for 72 hours and weighed. Regressions of aboveground biomass by stem height plus leaf area were then created (sun plants R2 = 0.76, P = 0.001; shade plants R2 = 0.55, P = 0.002). The resulting regression formulas were used to calculate aboveground biomass for the experimental seedlings. Amax and dark respiration were measured with a LI-COR 6400 gas exchange system (LI-COR, Nebraska, USA), and only one individual was measured in pots with competition. The third leaf from the apical meristem was measured for consistency in leaf age. Measurements were made between 7:00 and 13:00 hours. Leaves were clamped into an airtight cuvette with a red-blue LED light source. Incoming CO2 was set to 380 mmol/mol from a CO2 cartridge. Light response curves were made from darkness to 10, 25, 50, 100, 150, 200 mmol/s and continued in increments of 200 mmol/s until an asymptote was reached. Leaves were given 120 seconds to adjust to each light level, and the CO2 differential was recorded when flow rate, CO2 and humidity were constant. The flow rate was set to 550 mmol/s, and humidity was betweenVariation in Costs of Terpenoids and PhenolicsTable 1. MANOVA and profile analysis results for the response of Pentaclethra macroloba photosynthesis, biomass, and carbon-based metabolites (sugars, flavans, and saponins) to light, fertilizer, and competition.Photosynthesis and biomass Factor df MANOVA FPProfile F PSun plants Fertilizer Competition 2 1 0.2 0.05 0.8 0.8 2.4 2.8 0.1 0.Error Shade plants Fertilizer Competition20.97 8.0.4 0.0.8 0.0.5 0.Error Metabolites Factor Sun plants Fertilizer CompetitiondfMANOVA FPProfile F P20.2 19.0.8 0.0.2 19.0.8 0.Error Shade plants Fertilizer Competition Fert. * comp. Error2 1 20.8 0.2 5.0.5 0.6 0.1.1 0.03 0.0.4 0.