Chlorophyll a fluorescence and photosystem activities in
the trangenics
Chl a fluorescence has been used as a non-invasive signature of
photosynthesis, particularly of PSII (Krause and Weis, 1991; Strasser
and Srivastava, 1995; Papageorgiou and Govindjee (eds), 2004; Baker,
2008; Stirbet et al., 2018). When a dark-adapted photosynthetic organism
is exposed to blue light (λ- 460 mm), Chl a fluorescence rises
from a low initial minimum level (F o) to a high
level (F m) (Munday and Govindjee, 1969a; Munday
and Govindjee, 1969b). The CA over-expressers had higherF o (Table 2 ) partly due to higher Chl
content. However, there could be several other reasons to have higherF o in the transgenics, e.g., higher concentration
of QB- in dark-adapted
samples (Schreiber and Armond, 1978; Cao and Govindjee, 1990; Yamane et
al., 1997). However, the maximum primary photochemical efficiency of
PSII, as inferred fromF v/F m in dark-adapted
leaves, was ~5% higher in the transgenic plants
demonstrating higher efficiency of PSII (Genty et al., 1992; Baker et
al., 2007).