Combined Stresses in Plants: Physiological, Molecular, and Biochemical Aspects

168 V. G. Kakani et al.

ture (T2 and T4) treatments irrespective of irrigation treatment. Amount of irrigation
given was higher in T3 and T4 treatments due to greater ET demand associated with
the increase in ambient temperature in the second sowing.
Sowing date and temperature treatments significantly affected WUE (Table 8.4).
At ambient temperature, WUE was higher in T1 (sowing 1) than T3 (sowing 2), and
this was associated in part with a lower VPD. The highest WUE, 1.21 g m−2^ L−1, was
recorded in T2, and both high-temperature treatments, T2 and T4, increased WUE
compared to their respective ambient controls.
WUE was strongly affected by VPD, which was lower at sowing 1 (T1) than
sowing 2 (T3). The normalized values of WUE for T1 and T3 were 1.6 and 1.3 g
kPa L−1, respectively. The higher WUE at sowing 1 was probably due to cooler
mean temperatures (Table 8.1). The higher WUE in T4 compared to T3 is accounted
for by the lower VPD in T4, which in turn is due to the high RH in the heat tunnel.
Although RH was not measured in T2, RH was very high in the heat tunnel, and
the high WUE in T2 is undoubtedly due to a higher RH. Accordingly, T2 has been
excluded from further analysis.
No interaction between these factors could be recorded for WUE. Water stress
treatments did not influence WUE. Main effects of temperature and cultivar were
significantly affected by WUE. Genotype ICGS 11 recorded significantly ( p < 0.01)
higher WUE of 0.74 g m−2^ L−1 compared to 0.65 g m−2^ L−1 in TMV 2.

8.3.4 Effects of Temperature × Water Stress Interactions

Table 8.5 shows the interaction effects for temperature and water stress treatments.
The effects of temperature and water stress interaction were apparent only in the

Development stage TI and T2 IR WS T3 and T4 IR WS

Sowing–R1 121 121 204 204

R1–R3 98 43 201 89

R3–R8 355 183 234 91

Table 8.3 Cumulative
amounts of irrigation
(mm) supplied to irrigated
(IR—100 % of ETC) and
water stress (WS—40 % of
ETC) plots during different
stages of development

Temperature

treatments

WUE VPD WUE normalized

for VPD

T1 0.88 1.82 1.6

T2 1.21 NA NA

T3 0.58 2.26 1.3

T4 0.64 2.06 1.3

SED 0.055***

*** indicates significance at 0.001 level of probability

Table 8.4 Effect of
temperature treatments
on WUE (g L−1) and VPD
(kPa) and normalized
WUE (WUE × VPD
(g kPa L−1)