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

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harvests made immediately after ending the 20-day high-temperature treatment.
This interaction disappeared as the crop reached maturity. The interaction was sig-
nificant (< 0.05) between T3 and T4 for both peg and pod number at 54 DAS. High
temperature imposed in the irrigated treatment (IR) decreased the peg (50 %) or
pod (54 %) number. Water stress (WS) treatmentals reduced peg (68 %) and pod
(72 %) number under ambient temperature conditions. However, a combination of
high temperature (T4) and water stress (WS) increased peg, and in particular pod,
number relative to WS or T4. In general, water stress effects were more severe than
high-temperature effects.

8.3.5 Effects of Water Stress and Its Interaction with Genotypes

Water stress treatments significantly ( p < 0.05) altered the specific leaf area (SLA)
of the plants. There was no water stress x sowing interaction for SLA values, but
within a sowing there were differences between water stress treatments for SLA.
The SLA values recorded in irrigated conditions was lower (180.3 cm−2^ g) in sowing
2 compared to the values in sowing 1 (192.2 cm−2^ g). Treatment WS (40 % ETC)
increased the SLA in sowing 1 (201.2 cm−2^ g), while it decreased the SLA in sowing
2 (163.8 cm−2^ g).
Seasonal time course of biomass and pod weight in T1 is shown in Fig. 8.4. There
was no immediate effect on biomass or pod weights of the 20-day high-temperature
period. However, water stress treatment decreased biomass and pod weight through-
out the stress period.
The main effects of water stress were recorded only for biomass due to signifi-
cant ( p < 0.05) reduction in vegetative and pod weight. Vegetative (283.9 g m−2) and
pod weight (120.2 g m−2) in irrigated treatments (100 % ETC) were reduced by 20
and 37 %, respectively, due to water stress treatment (40 % ETC).

8 Effect of High Temperature and Water Stress on Groundnuts ...

Water stress treatments Temperature treatments

T3 (29 °C) T4 (31 °C)

Peg number

Irri 15.81 7.96

WS 6.60 8.09

SED 2.35*

Pod number

Irri 3.72 1.74

WS 1.03 2.84

SED 0.76*

Irri irrigated, WS water stress

* indicates significance at 0.05 level of probability

Table 8.5 Effects of
temperature (mean of
20-day high temperature)
and water stress
treatments on peg and
pod number (plant−1)
recorded in the harvest
made immediately after
the withdrawal of high-
temperature treatments