Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành y học dành cho các bạn tham khảo đề tài: Effects of manganese-excess on CO2 assimilation, ribulose-1,5-bisphosphate carboxylase/oxygenase, carbohydrates and photosynthetic electron transport of leaves, and antioxidant systems of leaves and roots in Citrus grandis seedlings | Li et al. BMC Plant Biology 2010 10 42 http 1471-2229 10 42 BMC Plant Biology RESEARCH ARTICLE Open Access Effects of manganese-excess on CO2 assimilation ribulose-1 5-bisphosphate carboxylase oxygenase carbohydrates and photosynthetic electron transport of leaves and antioxidant systems of leaves and roots in Citrus grandis seedlings Qing Li1 2 Li-Song Chen1 2 3 Huan-Xin Jiang1 4 Ning Tang1 2 Lin-Tong Yang1 2 Zheng-He Lin1 Yan Li5 Gang-Hua Yang1 4 Abstract Background Very little is known about the effects of manganese Mn -excess on citrus photosynthesis and antioxidant systems. Seedlings of sour pummelo Citrus grandis were irrigated for 17 weeks with nutrient solution containing 2 gM control or 500 gM excess MnSO4. The objective of this study were to understand the mechanisms by which Mn-excess leads to a decrease in CO2 assimilation and to test the hypothesis that Mn-induced changes in antioxidant systems differ between roots and leaves. Results Mn-excess decreased CO2 assimilation and stomatal conductance increased intercellular CO2 concentration but did not affect chlorophyll Chl level. Both initial and total ribulose-1 5-bisphosphate carboxylase oxygenase Rubisco activity in Mn-excess leaves decreased to a lesser extent than CO2 assimilation. Contents of glucose fructose starch and total nonstructural carbohydrates did not differ between Mn-excess leaves and controls while sucrose content was higher in the former. Chl a fluorescence OJIP transients from Mn-excess leaves showed increased O-step and decreased P-step accompanied by positive L- and K-bands. Mn-excess decreased maximum quantum yield of primary photochemistry Fv Fm and total performance index PItot abs but increased relative variable fluorescence at I-steps VI and energy dissipation. On a protein basis Mn-excess leaves displayed higher activities of monodehydroascorbate reductase MDAR glutathione reductase GR superoxide dismutase SOD catalase CAT and guaiacol peroxidase GPX and
