Physiological and biochemical response of potato (Solanum tuberosum L. cv. Kara) to O₃ and antioxidant chemicals: possible roles of antioxidant enzymes

Abstract

An Egyptian cultivar of potato (Solanum tuberosum L. cv. Kara) was grown in the field at two locations in northern Egypt: a 'rural ' and a 'suburban' site, from October 2000 and November 2002. The antiozonant ethylenediurea (EDU) and the fungicide chlorothalonil (1,3-benzenedicarbonitrile-2,4,5,6 tetrachloroisophthalnitrile) were applied as a foliar spray to plants at both sites. It was found that foliar injury symptoms were reduced greatly in plants treated with EDU and/or chlorothalonil, and the yield of treated plants was higher than that of the untreated ones, with the EDU having a greater protection than chlorothalonil. Antiozonant (EDU) and fungicide (chlorothalonil) combination sprays were even more effective in reducing O 3 injury. Moreover, the percentage of protection was higher in the rural area than in the suburban one, and this was associated with higher levels of O 3 recorded in the rural area. The response to O 3 , EDU, and chlorothalonil of the leaf antioxidant scavenger system was examined. Antiozonant-treated plants had the highest reduced glutathione/oxidised glutathione ratio. The results suggest that EDU and chlorothalonil do not act directly as antiozonant to inhibit O 3 injury but act through maintaining some antioxidant enzymes during O 3 exposure. To the best of knowledge, this is the first report demonstrating the marked enhancement of yield and plant oxidative enzymes by fungicides as a mechanism of protecting plants against noxious oxidative stress from the environment in the developing world.

Assessment of Ethylene Diurea-Induced Protection in Plants Against Ozone Phytotoxicity

“…Later studies utilized repeatitive (weekly or biweekly) EDU applications to protect plants against chronic O 3 exposures (Clarke et al 1983Hofstra et al 1983;Bambawale 1986;Heggestad 1988;Brennan et al 1990;Legassicke and Ormrod 1981;Toivonen et al 1982). Additional studies utilized variable dosages of EDU (300-500 ppm) to protect plants from acute and chronic O 3 levels, viz., 300 ppm (Hassan 2006), 400 ppm (Wahid et al 2001;Singh and Agrawal 2009;Singh et al 2009b) and 500 ppm (Agrawal et al 2004. Tiwari et al (2005) and Wang et al (2007) conducted dose-response studies on wheat.…”

“…Such information is useful for selecting cultivars to grow in areas that experience high O 3 levels . Yield loss assessments are performed by comparing the yield estimates of EDU-treated and untreated plants in O 3 polluted areas of the USA (Ensing et al 1985;Smith et al 1987), Asia (Wahid et al 2001;Agrawal et al 2004Agrawal et al , 2005Tiwari et al 2005;Wang et al 2007;Singh and Agrawal 2009;Singh et al 2010b, c), Africa (Hassan et al 1995;Hassan 2006) and Europe (Ribas and Penuelas 2000;Brunschon-Harti et al 1995a;Pleijel et al 1999). Yield increments after the application of EDU onto O 3 exposed plants have been reported for onion (Wukasch and Hofstra 1977), navy bean (Hofstra et al 1978;Temple and Bisessar 1979;Toivonen et al 1982), tomato (Legassicke and Ormrod 1981), potato (Bisessar 1982;Clarke et al 1990;Hassan 2006), tobacco (Bisessar and Palmer 1984), watermelon (Fieldhouse 1978), peanut (Ensing et al 1985), radish (Kostka-Rick and Manning 1992;Hassan et al 1995), carrot (Tiwari and Agrawal 2010), bush bean (Kostka-Rick and Manning 1993a, c), snap bean (Vandermeiren et al 1995), mungbean Singh et al 2010b), soybean (Wahid et al 2001), wheat (Agrawal et al 2004;Tiwari et al 2005;Wang et al 2007;Singh and Agrawal 2009) and black gram …”

“…Lee et al (1997) suggested that EDU protection against O 3 damage may result from maintenance of GR and GSH levels during O 3 exposure. Hassan (2006) used the same technique to determine the glutathione concentration in potato leaves. EDU-treated plants grown under O 3 exposure had a higher GSH content, but lower GSSG and total glutathione levels, compared to plants exposed to O 3 without EDU treatment.…”

“…Because of its oxidative capacity, high O 3 levels in the atmosphere are detrimental to living organisms, including plants. Ozone is among the most damaging air pollutants to which plants are exposed, and produces substantive plant biomass and yield (seed weight) reductions (Thompson 1992;Agrawal et al 2005;Manning 2005;Hassan 2006;Hassan and Tewfik 2006;Singh et al 2009aSingh et al , 2014Wahid 2006 a, b;Sarkar and Agrawal 2010a, b;Tripathi and Agrawal 2013). The economic loss for 23 horticultural and agricultural crops from O 3 exposure was estimated to be approximately $6.7 billion for the year 2000 in Europe (Holland et al 2006).…”

Effects of the Antiozonant Ethylenediurea (EDU) on Fraxinus ornus L.: The Role of Drought

“…However, the protective mechanism of EDU is still not fully understood [18]. Some studies [34][35][36] have shown that EDU acts by maintaining a high antioxidant enzyme activity and level during O 3 exposure, but other studies concluded that EDU does not significantly affect the antioxidant content in leaves [24]. It is also unclear whether EDU limits stomatal O 3 uptake by inducing a decrease in the stomatal conductance of treated plants [16,17].…”