Abstract:
Nineteen bread wheat genotypes were selected to exa
mine the effect of glycine betaine
(GB, 100 mM) on various photosynthetic gas exchange
parameters under drought stress
and to study the relationship of these parameters w
ith non-enzymatic antioxidants.
Drought stress caused a significant decline in net
CO
2
assimilation rate (P
n
), stomatal
conductance (g
s
), intercellular CO
2
concentration (C
i
) and transpiration rate (E) among
the studied wheat genotypes, with the tolerant geno
types characterized by higher net
photosynthetic rate, lower drought susceptibility i
ndex (DSI), and higher maintenance of
glutathione content (GSH) and ascorbic acid (AsA) l
evels than the sensitive ones. GB
application significantly improved the photosynthet
ic characteristics, particularly
P
n
and
g
s
, of studied wheat genotypes which could be due to
more utilization of glutathione and
increased levels of ascorbic acid in flag leaves un
der drought stress. But this response was
observed to be genotype specific. Positive correlat
ion of AsA with
DSI
in GB treated
plants, and of
P
n
with GSH under drought stress and GB applied condi
tions suggested the
role of these non-enzymatic antioxidants in sustain
ing photosynthetic efficiency and yield
stability under prolonged field drought stress cond
itions.
Keywords:
Non-enzymatic antioxidants, Photosynthetic efficie
ncy.
