THE EFFECTS OF ELEVATED CO2 ON PLANTS: III. FLOWER, FRUIT AND SEED PRODUCTION AND ABORTION

Abstract

Four populations of Phlox drummondii and one population each of Datura stramonium and Abutilon theophrasti were grown in six growth chambers at 300, 600 and 900 μ l l−1CO2, all other environmental variables remaining constant. Changes in timing and numbers of flowers produced were species‐ and population‐dependent. In general, P. drummondii and D. stramonium flowered earlier under high CO2 while A. theophrasti was not affected. Significant population × CO2 interactions were found for several flower production characters in P. drummondii, indicating differential response to elevated CO2 levels even within a species. In D. stramonium, increased biomass in high CO2 caused significantly larger fruits to be formed, but there was no significant increase in seed number. In A. theophrasti, individual seed weight increased with increasing CO2, but total seed weight per plant remained constant. These results are discussed in relation to their possible implications to plant community structure, and the effects on higher trophic levels (e.g. pollinators and plant predators). Qualitative as well as quantitative changes in plants in response to high CO2 must be studied with care to ensure correct predictions of the effects of the global rise in CO2. Copyright © 1984, Wiley Blackwell. All rights reserved