Abstract:
Terminal drought stress during grain filling period
has recently become more common
in the semiarid Mediterranean regions, where wheat
(
Triticum aestivum
L.) is grown as an
important winter cereal crop. The objective of this
experiment was to study the effect of
terminal drought stress on grain yield, gas exchang
e variables, and some physiological
traits of nine bread wheat cultivars. An experiment
was carried out in a split-plot
arrangement using randomized complete blocks design
with three replications during the
2010-2011 season at the research farm of Razi Unive
rsity, Iran. Based on the results
obtained, post anthesis water deficit significantly
decreased grain yield, biomass, 1,000
grain weight, and harvest index of wheat cultivars.
Under terminal drought stress and
control treatments, there were significant differen
ces between cultivars in terms of all
traits studied. Also, terminal drought stress decre
ased leaf net photosynthesis rate (P
n
),
stomatal conductance (g
s
), transpiration rate, Chlorophyll a, b, and a/b, a
nd increased
leaf temperature and sub-stomatal CO
2
concentration. Cultivars differed in their
response to water stress. In general, tolerant cult
ivars showed a higher
P
n
and
g
s
and leaf
water content under both moisture conditions compar
ed with susceptible ones. A greater
reduction in
g
s
and transpiration rate and smaller reduction in P
n
under stress condition
led to a remarkably higher photosynthetic water use
efficiency of the tolerant cultivars.
Finally, it can be concluded that planting wheat va
riety DN-11 in areas with post-anthesis
water stress was recommendable for maximizing grain
yield.
Keywords
: Photosynthesis, Relative water content, Stress su
sceptibility index, Water use
efficiency
