136 S. Signorelli et al.
Among the oxidative stress markers, synergistic effect was the most
commonly observed response. Most stresses are accompanied by an increment
of ROS production, and the source of ROS is different for different stresses
(Mahalingam and Fedoroff 2003 ; Wrzaczek et al. 2013 ). Thus, when more than
one stress is present, it induces ROS from different organelles, and hence the
total ROS tends to be higher in combined stress scenarios. Less commonly, a
negative correlation or an unchanged response is observed. In one case of negative
correlation observed for H 2 O 2 , it was suggested that the reduction in SOD activity
in combined stress as opposed to in single stress was responsible for the lower H 2 O 2
in the former. In the other case, induction of CAT activity only in the combination
of stress was suggested to be the cause of lower H 2 O 2 levels.
(^) Table 6.1 Effects of stress combination on main parameters studied in legumes
Response
Evaluated
parameter
Negative
correlation
Unchanged Additive
response
Synergistic
effect
APX
SOD
Antioxidant enzymes C AT
GR
POX
H 2 O 2
Oxidative stress TBARS
Electrolyte leakage
O 2 ○-
Photosynthetic activity FV/FM
CP47
D1
D2
Metabolites Proline
Ascorbic acid
Darker shading indicates that the particular response is supported by more evidence. Data obtained
from following legume species under various combined stresses: L. corniculatus, T. pratense
subjected to combined drought and heat (Signorelli et al. 2013b), L. japonicus subjected to
combined drought and heat (Sainz et al. 2010 ), Vigna unguiculata subjected to combined CO 2 ,
UV-B radiation and temperature stress (Singh et al. 2010 ), Vigna radiata (Siddiqui 2013 )
and Phaseolus vulgaris subjected to combined zinc and high irradiance stress (Michael and
Krishnaswamy 2011 ).
APX ascorbate peroxidase, SOD superoxide dismutase, CAT catalase, GR glutathione reductase,
H 2 O 2 hydrogen peroxide, TBARS thiobarbituric reactive substances, O 2 ●− superoxide radical,
Fv/FM photosystem II, POX peroxidase