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Leaf RD (A) and leaf RL (B) of X. strumarium grown at ambient (open symbols) or elevated (closed symbols) CO2. Leaf RD and RL were measured at growth CO2 concentration on five different dates. Because there was no effect of planting date on RD or RL, all measurements from plants of different ages were averaged for each CO2 treatment. Arrow indicates date of flowering for all plants. Mean ± 1 SE; n = 18 for December 24, 1999, and n = 24 for all other dates. *, P < 0.05.
