Table III.

Characteristic photosynthetic features of tobacco plants with altered GA biosynthesis

Leaf 12Leaf 8
Wild TypeAtGA20-oxAtGA2-oxWild TypeAtGA20-oxAtGA2-ox
Maximum CO2 uptake (μmol m−2 s−1)15.8 ± 0.515.4 ± 0.320.0 ± 1.07.6 ± 0.38.0 ± 0.413.4 ± 0.3
Maximum quantum yield of CO2 fixation (mmol CO2 mol−1 quanta)0.058 ± 0.0010.059 ± 0.0010.060 ± 0.0010.053 ± 0.0020.051 ± 0.0010.059 ± 0.001
Fv/Fm0.830 ± 0.0030.830 ± 0.0020.841 ± 0.0020.811 ± 0.0040.802 ± 0.0040.838 ± 0.002
Chlorophyll (mg m−2)376 ± 9.2332 ± 8628 ± 26308 ± 14252 ± 12522 ± 14
  • Parameters were measured from different leaves of wild-type and transgenic plants expressing AtGA20-ox (no. 15) or AtGA2-ox (no. 41; number of leaves counted from bottom to top, plants at 16-leaf stage). Maximum CO2 uptake and maximum quantum yield of CO2 fixation were calculated from data of light response curves at light saturation or their initial slope, respectively. Each value represents the mean ± se of 18 to 20 or 8 to 11 (in case of data for Fv/Fm and chlorophyll content) independent measurements.