Figure 3.

Effect of decreased mMDH activity on photosynthesis. A, Photosynthetic assimilation and carbon partitioning at the onset of illumination. Leaf discs were cut from six separate untransformed potato plants and four independent transgenic lines at the end of the night and illuminated at 250 μmol photosynthetically active radiation m⁻² s⁻¹ in an oxygen electrode chamber containing air saturated with ¹⁴CO₂. After 30 min the leaf discs were extracted and fractionated. B, In vivo fluorescence emission was measured as an indicator of the ETR by use of a PAM fluorometer at PFDs of 250 (black bars) and 700 μmol m⁻² s⁻¹ (white bars). C, Assimilation rate. D, Transpiration rate. E, Stomatal conductance. The lines used were: wild type, black circles; AL21, white circles; and AL7, black triangles. Values are presented as mean ± se of determinations on six individual plants per line; an asterisk indicates values that were determined by the t test to be significantly different (P < 0.05) from the wild type.