Based on reports that variables related to photosynthesis(net assimilatory ratio and chloroplast pigments)are more plastic than the morphological and biochemical variables in a climax tropical species,Cariniana estrel...Based on reports that variables related to photosynthesis(net assimilatory ratio and chloroplast pigments)are more plastic than the morphological and biochemical variables in a climax tropical species,Cariniana estrellensis,under contrasting irradiance,we hypothesised that plasticity of gas exchange variables is higher in relation to growth,biochemical and anatomical variables.Plants that were 14 months old were subjected to200 up to 2000 lmol m^(-2)s^(-1) of photo synthetically active radiation(PAR)for 140 days.Growth increased up to1400 lmol m^(-2)s^(-1)PAR and then decreased at 2000 lmol m^(-2)s^(-1) PAR(full sunlight).This was related to the rate of photosynthesis(A)which showed the same tendency as photosystem Ⅱ performance index(PI_(ABS)).The greater thickness of the secondary xylem at 1400 lmol m^(-2)s^(-1) PAR indicated a higher water conductance capacity.The decrease in specific leaf area,elongation of mesophyll cells,and increase in stomatal density observed at higher irradiances were associated with higher leaf fructose and sucrose concentrations.We concluded that the better growth in partial shade was due to higher photosynthetic capacity.On the other hand,photosynthesis was inhibited equally in full sun and deep shade.The high adjustment capacity of C.estrellensis to wide amplitudes of irradiance was provided by greater plasticity of gas exchange variables in relation to growth,anatomical,and biochemical variables.展开更多
基金supported by the National Plan for the Support and Development of Botany-Coordination for the Improvement of Higher Education Personnel(PNADB–CAPES)(Process 1147/2010)the National Council for Scientific and Technological Development(CNPq)for the Science Productivity Scholarship(Process 305447/2012-2)
文摘Based on reports that variables related to photosynthesis(net assimilatory ratio and chloroplast pigments)are more plastic than the morphological and biochemical variables in a climax tropical species,Cariniana estrellensis,under contrasting irradiance,we hypothesised that plasticity of gas exchange variables is higher in relation to growth,biochemical and anatomical variables.Plants that were 14 months old were subjected to200 up to 2000 lmol m^(-2)s^(-1) of photo synthetically active radiation(PAR)for 140 days.Growth increased up to1400 lmol m^(-2)s^(-1)PAR and then decreased at 2000 lmol m^(-2)s^(-1) PAR(full sunlight).This was related to the rate of photosynthesis(A)which showed the same tendency as photosystem Ⅱ performance index(PI_(ABS)).The greater thickness of the secondary xylem at 1400 lmol m^(-2)s^(-1) PAR indicated a higher water conductance capacity.The decrease in specific leaf area,elongation of mesophyll cells,and increase in stomatal density observed at higher irradiances were associated with higher leaf fructose and sucrose concentrations.We concluded that the better growth in partial shade was due to higher photosynthetic capacity.On the other hand,photosynthesis was inhibited equally in full sun and deep shade.The high adjustment capacity of C.estrellensis to wide amplitudes of irradiance was provided by greater plasticity of gas exchange variables in relation to growth,anatomical,and biochemical variables.
