THE INFLUENCE OF ELEVATED CO2 AND TEMPERATURE ON SEED-GERMINATION ANDEMERGENCE FROM SOIL

Seed of six crop species, alfalfa, Medicago sativa L. cv. 'Arc', soybe an, Glycine max L. (Merrill) cv. 'Williams', maize, Zea mays L. cv. SS 885, pea, Pisum sativum L. cv. 'Maestro', sunflower, Helianthus annuu s L. cv. 'Mammoth', and pumpkin Cucurbita pepo L. cv. 'Big Max' and fo ur weedy species, Amaranthus hypochondriacus L., Amaranthus hybridus L ., Chenopodium album L. and Abutilon theophrasti, were grown at two di fferent CO2 concentrations of 350 mul l-1 (ambient) and 700 mul l-1 (e levated) in controlled-environment chambers to determine the effect of elevated CO2 on germination and emergence. Doubling the CO2 concentra tion resulted in an increase in the rate and final percentage of germi nation, for M. sativa, A. hybridus and C album. In a separate field ex periment (silt-loam soil), elevated CO2 resulted in a significant incr ease in the total number of weed seedlings present 3 weeks after tilli ng. In a second set of experiments using controlled-environment chambe rs, the interaction between increased temperature and CO2 was examined in seven of the species used previously. No significant interaction w as observed between CO2 and temperature on the germination response. O verall, this investigation suggests that as CO2 increases, differentia l changes in germination and/or emergence between crops and weeds coul d occur.