Response of tomato to defoliation and elevated CO[sub 2]level

Increased resources are expected to result in increased plant productivity and to increase a plant's ability to replace tissue lost to defoliation. This hypothesis was tested by growing tomato plants (Lycopersicon esculentum) in a phytotron greenhouse at ambient (355 ppm) and elevated (710 ppm) levels of CO[sub 2]. The experiment was fully factorial for CO[sub 2] level and two manual defoliation treatments, the first during vegetative growth and the second during fruiting. Elevated CO[sub 2] level did not alter total biomass, but did alter allocation: total fruit biomass and fruit number decreased. This is contrary to the expected result. Only the first defoliation treatment lowered total vegetative and reproductive biomass produced. There was no interaction between response to defoliation and response to elevated CO[sub 2] level. Thus, both the main effect of elevated CO[sub 2] and the interaction of defoliation and elevated CO[sub 2] were inconsistent with my hypothesis.