Leaf gas exchange and carbohydrates in tropical trees differing in successional status in two light environments in central Amazonia

Abstract

Monoculture and mixed stands of mahogany (Swietenia macrophylla King) and tonka bean (Dipteryx odorata Willd.) trees were established on degraded land in central Amazonia to compare leaf gas exchange parameters between plants grown in sunlight in an open field and in shade beneath a balsa wood (Ochroma pyramidale Cav.) canopy. Shading increased specific leaf area by about 50% in both species. Shading reduced height and diameter growth of S. macrophylla, whereas it increased these parameters for D. odorata. Light-saturated photosynthesis (Amax), stomatal conductance (gs) and transpiration (E) were higher in S. macrophylla than in D. odorata. In S. macrophylla, Amax was higher in sun leaves (12.9 +/- 0.9 micromol m-2 s-1) than in shade leaves (10.2 +/- 1.0 micromol m-2 s-1), whereas light environment had no significant effect on Amax of D. odorata. In both species, CO2-saturated photosynthesis (Apot) was higher in sun leaves (22 +/- 1.4 micromol m-2 s-1) than in shade leaves (17-20 +/- 0.8 micromol m-2 s-1). Stomatal conductance and E increased in sun leaves of S. macrophylla by 45 and 38%, respectively, whereas light environment did not affect gs and E of D. odorata. Photorespiration rates (Pr) varied from 28 to 36% of net photosynthesis (A) at ambient atmospheric CO2 concentration (Ca) but declined to around 7% of A at higher Ca. Leaf dark respiration (Rd) and the CO2 compensation point (Gamma) were lower in shade-grown plants than in open-grown plants. Compared with shade-grown plants, total nonstructural carbohydrate (TNC) concentrations increased by 56% in S. macrophylla and by 30% in D. odorata in the open field. Leaf nitrogen (NL) concentrations were higher in open-grown plants than in shade-grown plants of both species, and TNC and NL concentrations were negatively correlated (r = -0.77). High TNC accumulation in S. macrophylla in the open field suggests that photosynthesis is unlikely to be growth-limiting at this site. We conclude that photosynthetic parameters of D. odorata are less affected by light environment than those of S. macrophylla, indicating that D. odorata has lower physiological plasticity to light than S. macrophylla.

Photosynthetic analyses of two native Atlantic Forest species in regenerative understory of eucalyptus plantation

“…The values of the gas exchange variables registered in the present study for X. sericea and S. guianensis are situated within the parameters observed for other tropical tree species (Baker et al, 1997;Eschenbach et al, 1998;Marenco et al, 2001;Costa and Marenco, 2007;Gonçalves et al, 2009;Silva et al, 2010). The species X. sericea and S. guianensis exhibited high values of correlation between A and g s in the dry season, suggesting that their stomata respond significantly to the variations in light and water availability.…”

Fotossíntese, condutância estomática e potencial hídrico foliar em árvores jovens de andiroba (Carapa guianensis)

“…hipótese não parece provável porque a irradiância observada durante a maior parte do dia (menos de 1000 µmolm -2 s -1 ) foi menor do que a requerida para saturar a fotossíntese em espécies de crescimento rápido aclimatadas ao sol, tais como Swietenia macrophylla (King.) (Marenco et al, 2001a), Ochroma pyramidale (Urban.) (Marenco et al, 2001b) e Cedrela odorata (L.) (Maruyama et al, 2005).…”

Morphological and physiological adjustments of Brazilwood (Caesalpinia echinata Lam.) to direct solar radiation

“…The decrease in the ratios Chl a:b and Chl total :Carot in plants of C.echinata after periods of exposure to direct sunlight (Figure 4) is one of the immediate responses of shade species when exposed to higher irradiance (Demmig-Adams and Adams, 2006;Morais et al, 2007;Magalhães et al, 2009) light-gathering antennas (Kitajima and Hogan, 2003;Laisk et al, 2005;Magalhães et al, 2009). This strategy protects the photosystems from photo-oxidative damage caused by high irradiance (Tan et al, 2000;Marenco et al, 2001;Reyes-Díaz et al, 2009). However, the continuous reduction in photosynthetic pigments after exposure of C. echinata to full sunlight shows its preference for less illuminated environments.…”

“…The specific leaf area (SLA) is also subject to variations in the concentration of soluble carbohydrates combined with intense irradiance (Lambers and Poorter, 2004). In some trees, SLA (Valladares et al, 2005) and the concentration of carbohydrates (Marenco et al, 2001) increased in plants under full sunlight.…”