Abstract
The present study focused on assessing the effects of jasmonic acid (JA) seed treatment on the physiology of Brassica juncea seedlings grown under imidacloprid (IMI) toxicity. It has been observed that IMI application declined the chlorophyll content and growth of seedlings. However, JA seed treatment resulted in the significant recovery of chlorophyll content and seedling growth. Contents of oxidative stress markers like superoxide anion, hydrogen peroxide, and malondialdehyde were enhanced with IMI application, but JA seed treatment significantly reduced their contents. Antioxidative defense system was activated with IMI application which was further triggered after JA seed treatment. Activities of antioxidative enzymes and contents of non-enzymatic antioxidants were enhanced with the application of IMI as well as JA seed treatment. JA seed treatment also regulated the gene expression of various enzymes under IMI stress. These enzymes included respiratory burst oxidase (RBO), Ribulose-1,5-bisphosphate carboxylase/oxygenase (RUBISCO), NADH-ubiquinone oxidoreductase (NADH), carboxylesterase (CXE), chlorophyllase (CHLASE), cytochrome P450 monooxygenase (P450). JA seed treatment up-regulated the expressions of RUBISCO, NADH, CXE, and P450 under IMI toxicity. However, expressions of RBO and CHLASE were down-regulated in seedlings germinated from JA seed treatment and grown in presence of IMI. Seed soaking with JA also resulted in a significant reduction of IMI residues in B. juncea seedlings. The present study concluded that seed soaking with JA could efficiently reduce the IMI toxicity by triggering the IMI detoxification system in intact plants.
Highlights
Food demands are continuously increasing due to the rapid population growth throughout the globe
In order to study the mechanism behind the role of jasmonic acid (JA) in B. juncea, we studied the expression of some important genes encoding enzymes which are responsive to oxidative stress and pesticide detoxification (NADH-ubiquinone oxidoreductase, carboxylesterase and cytochrome P450 monooxygenase)
A significant recovery by 50, 87.9, 56.6, and 48.52% was noticed in seed germination, hypocotyl length, hypocotyl fresh weight and radicle length, respectively, when seedlings raised from JA treated seeds and germinated in presence of IMI (200 mg·L−1) were compared to only IMI treated (200 mg·L−1) seedlings
Summary
Food demands are continuously increasing due to the rapid population growth throughout the globe. Similar to other xenobiotic compounds, translocation of IMI from soil to the aerial parts (mainly leaves) of plants takes place through xylem It moves into the flowers, fruits and other plant parts via phloem sap (Laurent and Rathahao, 2003; Alsayeda et al, 2008). Residues of this neonicotinoid insecticide are translocated to the pollens as well as to the nectar (Stoner and Eitzer, 2012). Persistence of IMI is so long that in some cases, even no IMI is used in a particular season (but applied in previous seasons), its residues still persist in soil and get translocated into plant parts (Benton et al, 2015)
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