Behboudian. and Lai (1994) found tomatoes CO2 enriched at 22 celsius did not grow any more rapidly than non-enriched plants in most of the enrichment treatments. At 25 celsius, there was a growth response overall, but only if enrichment continued for at least 8 h. Four hours of enrichment actually decreased growth significantly compared to the ambient CO2 treatment. Exposing plants to high CO2 at 22°C for half the week was also ineffective in terms of increasing growth They suggested that lower translocation rates in CO2 enriched plant meant that photosynthates accumulated in leaves rather than contributing to leaf expansion.