Resumo

GONCALVES, José Francisco de Carvalho et al. Growth, photosynthesis and stress indicators in young rosewood plants (Aniba rosaeodora Ducke) under different light intensities. Braz. J. Plant Physiol. [online]. 2005, vol.17, n.3, pp. 325-334. ISSN 1677-0420.  http://dx.doi.org/10.1590/S1677-04202005000300007.

Aniba rosaeodora is an Amazonian tree species that belongs to the family Lauraceae. Due to intense exploitation for extraction of essential oils (mainly linalol), A. rosaeodora is now considered an endangered species. On the other hand, there is little information about its ecophysiology which would be useful to support future forest planting programs. Hence, the effect of different light intensities on the growth and photosynthetic characteristics of young plants of A. rosaeodora was studied. Nine-month-old plants were subjected to four light treatments (T₁= 10 a 250 µmol.m^-2.s^-1 / control; T₂=500 to 800, T₃=700 to 1000 and T₄=1300 to 1800 µmol.m^-2.s^-1 / full sunlight). Allometric variables, gas exchange, contents of pigments and chlorophyll a fluorescence were analysed. As to the relative growth rates, it was found that plants of A. rosaeodora showed higher biomass accumulation when grown under intermediary irradiance conditions (T₂). The best photosynthetic performance was achieved under conditions of T₃. When growth was correlated with photosynthesis, it was found that plants under treatments T₂ and T₃ presented better responses in comparison with the lowest (T₁) and highest (T₄) light extremes. The highest pigment contents were obtained for plants in the shade (T₁) and the lowest for those exposed to full sunlight (T₄). The photochemical efficiency of photosystem II (F_v/F_m) was found that only plants in the shade treatment (T₁) presented no stress from high irradiance. These findings suggest that both treatments (T₁ and T₄) altered the function of the A. rosaeodora plants, inhibiting photosynthesis and growth. Plants of A. rosaeodora developed photo-protection mechanisms under full sunlight. However, the species presented better photosynthetic response and biomass gain under intermediary irradiance conditions, displaying relative physiological plasticity, during the seedling phase.

Palavras-chave : chlorophyll a fluorescence; chloroplast pigment contents; gas exchanges; photochemical efficiency of photosystem II; relative growth rate; tropical species.