Figure 1.

Seasonal changes in ice nucleation temperatures of leaves of Maidenhair tree after long-term (5 years) growth at ambient (□) and elevated (▪) CO₂ partial pressures. Values are means of four leaves, one per plant at each CO₂ partial pressure ± se. All measurements were made mid-month. All differences between means at ambient and elevated CO₂ partial pressures were significant (P < 0.001, two sample t tests).