Apidologie 28 (1997) 43-55
DOI: 10.1051/apido:19970105

Nectar and flower production in Vicia faba L. (field bean) at ambient and elevated carbon dioxide

J.L. Osborne^a, C.S. Awmack^{a, b}, S.J. Clark^c, I.H. Williams^a and V.C. Mills<sup>a

a</sup>  Department of Entomology and Nematology, IACR-Rothamsted
^b  NERC Centre,for Population Biology, Imperial College, Silwood Park, Ascot, Berkshire SL5 7PY, UK
^c  Department of Statistics, IACR-Rothamsted, Harpenden, Hertfordshire AL5 2JQ

Abstract - Atmospheric CO₂ has been predicted to double by the year 2100. Elevated CO₂ causes an increase in photosynthetic rate and extra assimilate is allocated to plant growth, seed and fruit production. Increased investment in flowers may have implications for pollination in entomophilous plants. Floral nectar standing crop, flower production and longevity were examined in Vicia faba, field bean, at ambient and elevated CO₂. Nectar standing crop did not differ significantly between treatments but plants grown at elevated CO₂ produced approximately 25% more flowers per plant and these lived 17% longer than those grown at ambient CO₂. A plant grown at elevated CO₂ may thus produce more nectar in total and, together with its increased floral display, may be more attractive to pollinators, but pollen flow will not necessarily be improved.

Key words: Vicia faba / carbon dioxide / climate change / nectar / flower longevity