Fig. 2.

Elevated levels of BiP confer drought tolerance to soybean plants under a restricted water regime. (A) Overexpression of BiP maintains leaf turgidity under drought. Drought stress was induced by reducing irrigation to 40% of the daily normal water supply. The leaves were photographed on day 18 of the experiment. (B) Leaf water potential of transgenic leaves under drought stress (reducing daily irrigation). Each value represents the mean ±SD of five replicates from three independent experiments. The asterisks indicate significant differences at P ≤0.05 as compared to the wild type. I, normally irrigated; DS, drought stress. (C, D, E) Photosynthesis and water relations in soybean transgenic lines continuously irrigated or exposed to the drought regime. Photosynthetic rate (C), stomatal conductance (D), and transpiration rate (E) of the third fully expanded leaf of WT and transgenic lines (as indicated) were measured by the LI-6400 infrared (IR) gas analyser at 1000 μmol m⁻² s⁻¹ irradiance. I, control leaves (normal irrigation). DS, leaves after 18 d of drought stress (40% of normal daily irrigation). After 18 d under the restricted water regime, the plants were rewatered with a normal water supply for 5 d (RW-5d) or 14 d (RW-5d). Each value represents the mean ±SD of five replicates from three independent experiments. The asterisks indicate significant differences at P ≤0.05 as compared to the wild type.