Agriculture Reference
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Kaushal et al. [191] reported that heat stress (45/40°C) induced the activities of enzymatic (SOD,
CAT, APX, GR) and levels of non-enzymatic (AsA, GSH) antioxidants. However, the plants
growing in the presence of proline reduced the oxidative injury which was coupled with
elevated levels of enzymatic and non-enzymatic antioxidants which indicated the upregula‐
tion of the antioxidant defense system could imparts partial heat tolerance to chickpea plants.
Recently, we investigated the effect of HT stress (38°C for 24 and 48 h) on antioxidant defense
system and the protective role of NO in coffering stress tolerance in T. aestivum L. cv. Pradip)
seedlings [Hasanuzzaman et al. 2012b]. We observed that AsA content markedly decreased
upon heat treatment but GSH and glutathione disulfide (GSSG) content increased. Heat
treatment resulted in an increase in the activities of antioxidant enzymes - APX, GR, GPX and
GST. However, supplementation of heat-treated seedlings with sodium nitroprusside (SNP)
significantly increased the content of AsA and GSH as well as the GSH/GSSG ratio [165]. Heat
treated seedlings which were supplemented with SNP also upregulated the activities of APX,
MDHAR, DHAR, GR, GST and CAT. This study clearly indicated the role of antioxidant
defense to develop stress tolerance in plant under HT. Bavita et al. [192] reported that the up-
regulation of the antioxidant system by NO possibly contributed to better tolerance against
HT induced oxidative damage in wheat.
A higher AsA content was found to associate with higher antioxidative capacity and higher
cold tolerance in rice [184]. Streb et al. [193] found to increase the contents of AsA and α-
tocopherol in chilling-tolerant cereal leaves which helped to maintain better photosynthesis
levels as compared to the chilling sensitive varieties. Fortunato et al. [194] stated that the
elevated ROS production indicated by H 2 O 2 and OH was reduced by the over production of
AsA and α-tocopherol contents under LT stress in Coffea sp. The ratio of GSH/GSSG is also
important because higher of this ratio is an indication for better tolerance to stress. Under
stressful condition including the cold the higher GSH/GSSG ratio is desirable for the sufficient
amount of GSH in the AsA-GSH cycle [195]. Takáč et al. [196] showed that the activities of
some antioxidant enzymes are partially correlated with the chilling sensitivity of maize
cultivars and thus the antioxidant enzymes posses a significant importance in the chilling
tolerance of Z. mays . In rice, a greater efficiency of antioxidant enzymes was observed in
chilling-tolerant cultivars and the activities of those were far higher than chilling-susceptible
cultivars [19]. Wang and Li [90] observed that both heat and cold altered the antioxidant
defense system in grape plants. However, exogenous salicylic acid (SA) pretreatment enabled
the grape leaves to maintain relatively higher activities of APX, GR, MDHAR, and redox ratio
in the AsA-GSH pool both under normal temperature and heat or cold stress. They also
suggested that Ca 2+ homeostasis and antioxidant systems are involved in SA-induced heat or
cold tolerance. Zhao et al. [189] observed that the chilling tolerance of tomato cultivars could
obviously be indicated by higher activities of CAT, APX, POX and SOD. Zhang et al. [2009]
found that chilling stress reduced the activities of antioxidant enzymes viz. SOD, POD, CAT
and APX in C. sativus . However, these changes were significantly restored by exogenous
application of putrescine (Put) and spermidine (Spd) which rendered the plants tolerant to
chilling. Zhao et al. [189] reported that the chilling tolerance of tomato cultivars could
obviously be designated by the higher activities of CAT, APX, POX and SOD enzyme. Chu et
al. [197] observed that Se treatments significantly increased the content of anthocyanins,
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