Effects of Mn-toxicity on gas exchange and Chl of Citrus grandis and C. sinensis leaves. (A-D) Leaf CO2 assimilation, transpiration, stomatal conductance and intercellular CO2 concentration. (E-G) Leaf concentrations of Chl a + b, Chl a and Chl b. (H) Leaf ratio of Chl a/b. Bars represent means ± SE (n = 4 or 5 ). Different letters above the bars indicate a significant difference at P < 0.05.