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Stem dry matter δ18O plotted against SD for seedlings of seven tropical tree species. The figure includes plants grown at both ambient (40 Pa) and elevated (70 Pa) CO2 partial pressure. SD was measured on abaxial leaf surfaces. The line is a least-squares linear regression: δ18O = −0.03SD + 23 (r2 = 0.29, P < 0.001, n = 80).
