Tolerance to paraquat-mediated oxidative and environmental stresses in squash (Cucurbita spp.) leaves of various ages

Paraquat: An Oxidative Stress Inducer

“…Although damage originated by paraquat treatment in Cucurbita spp varied among cultivars, the injury provoked by herbicide application was lower in younger leaves than in older ones as it was observed by lesser conductivity values and malondialdehide production which indicate membrane damage with cellular leakage and membrane lipid peroxydation respectively. These responses correlated also with higher antioxidant activity and increases in ascorbate content as well as with higher epicuticular wax in young leaves (Yeol Yoon , 2011).…”

Ameliorative effects of squash (Cucurbita moschata Duchesne ex Poiret) leaf extracts on oxidative stress

“…When the maize leaves were treated with the PQ pre-mixture containing WE from the 4th leaves of the squash plant (hereafter referred to as CmWE4), the alleviation effect was much greater and the level of leaf damage was only 20% of that generated by the PQ-only treatment, suggesting that higher amounts of putative functional ingredient(s) were present in younger leaves than in the older leaves of the squash plant. Similarly, the chlorophyll content, which is one of the indicators of leaf damage caused by oxidative stress (Mascher et al 2005;Yoon et al 2011), was higher in the PQ-CmWE4 treated maize leaves, indicating that CmWE4 plays a major role in alleviating the level of oxidative leaf damage (Fig. 1Bb).…”

“…The ascorbic acid (AsA) and dehydroascorbic acid (DHA) contents were measured using the method previously described elsewhere (Yoon et al 2011). Crude AsA and DHA were purified by homogenizing the leaf tissues with 5% metaphosphoric acid.…”

“…Either DQ (1 mM) or OF (1 mM) was pre-mixed with CmWE4 (0.1%) and sprayed onto the maize plants. Drought conditions were mimicked by equilibrating the water potential until the three true-leaf stage of the plants, after which no water was applied throughout the experiment as described previously (Yoon et al 2011). CmWE4 was sprayed foliarly onto the maize plants at three true-leaf stage and incubated under drought condition (described above) or cold condition (4°C for 24 h).…”

“…Upon a PQ foliar treatment, the younger leaves showed lower degrees of electrolyte leakage and lipid peroxidation than those of the older leaves. Similarly, the higher ascorbate peroxidase, glutathione reductase, and catalase activities were examined in younger leaves, suggesting that younger leaves exhibited more efficient antioxidative mechanisms than older leaves (Yoon et al 2011). On the other hand, the mechanism of tolerance in the younger leaves is still unclear.…”