Figure 3.

Electrolyte leakage rates of cellular membranes, expressed as R_c, of leaves of Maidenhair tree in response to the frosting treatments 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. No significant differences between CO₂ partial pressures for each CO₂ partial pressure, except at −6.5°C (P < 0.05, two sample t tests).