Effect of Drought Stress and Vesicular–arbuscular Mycorrhiza on Citrus Transpiration and Hydraulic Conductivity of Roots*

S ummary Infection of rough lemon seedlings ( Citrusjambhiri Lush) by the vesicular–arbuscular mycorrhizal (VAM) fungus, Glomus intraradices (Schenck and Smith), increased root growth and transpiration rate and reduced leaf water potentials relative to non‐infected control plants. Half of the VAM and control plants were subjected to three drying cycles each of 5 to 7 days. The hydraulic conductivity of previously drought stressed root systems was lower than that of the well‐watered plants and VAM infection further reduced root conductivity. These data suggest that the higher root densities and higher transpiration rates of VAM infected plants may have depleted soil water more quickly than the non‐infected seedlings and resulted in more severe water stress conditions during drought cycles.