Fig. 4.

The effects of CO₂, P and water regime on root length (A) and root length distribution of field pea in the 0–20 cm (20), 20–40 cm (40) and 40–60 cm (60) soil layers (B). Plants were exposed to ambient (aCO₂) or elevated CO₂ (eCO₂) treatments for 123 d in a P-deficient vertisol supplied with 15 (P15) or 60 mg P kg⁻¹ (P60) soil, and drought-stressed plants had water withheld until the soil reached the permanent wilting point in the last 3 weeks of the experiment. Columns are means of four replicates ± s.e. The vertical bars indicate the the LSD (P = 0.05).