Ethylene Potentiates Sulfur-Mediated Reversal of Cadmium Inhibited Photosynthetic Responses in Mustard

Abstract

The potential of exogenous ethylene and sulfur (S) in reversal of cadmium (Cd)-inhibited photosynthetic and growth responses in mustard (Brassica juncea L. cv. Pusa Jai Kisan) were studied. Plants grown with 50 μM Cd showed increased superoxide and H2O2 accumulation and lipid peroxidation together with increased activity of 1-aminocyclopropane carboxylic acid synthase (ACS) and ethylene production and inhibition of photosynthesis and growth. Application of 1 mM SO42- or 200 μL L-1 ethephon (ethylene source) influenced photosynthetic and growth performance equally in presence or absence of Cd. However, their combined application synergistically improved photosynthetic performance more in presence of Cd and reduced oxidative stress (lower superoxide and H2O2 accumulation) by decreasing ethylene and glucose sensitivity with the increase in cysteine and methionineand a non-proteinogenic thiol (reduced glutathione; GSH) contents. The central role of ethylene in potentiating S-mediated reversal of Cd-induced oxidative stress was evident with the use of ethylene action inhibitor, norbornadiene (NBD). The application of NBD resulted in decreased thiol production and photosynthetic responses. This suggests that ethylene promotes the effects of S in reversal of adverse effects of Cd, and thus, ethylene modulation may be considered as potential tool to substantiate the S effects in reversal of Cd inhibited photosynthesis and growth in mustard.

Treatment of nitric oxide supplemented with nitrogen and sulfur regulates photosynthetic performance and stomatal behavior in mustard under salt stress

“…In the present study, NO decreased content of H 2 O 2 and TBARS showing the capability of NO in mitigation of salt-induced oxidative stress (Table 1). These findings are in accordance with the earlier reports by Bai et al (2011), Fatma et al (2016 and Per et al (2017), that NO application alters the antioxidant system and protects plants against salt stress.…”

“…Salt stress decreased chlorophyll content, maximum quantum efficiency of PSII photochemistry (Fv/Fm), electron transport and quantum yield of PSII, with partial stomata closure (Steduto et al , Mehta et al ). Earlier research has shown the reduction in chlorophyll fluorescence and disruption of antenna pigments by the barrier of electron transport flow from PSII to PSI under heavy metal stress (Parmar et al , Khan et al ). In the present study, application of NO improved Fv/Fm, Fv′/Fm′, ΦPSII, qP and ETR, however, non‐photochemical quenching (NPQ) was reduced (Fig.…”

“…S serves as key nutrient with fundamental roles in developing tolerance to various stresses (Iqbal et al ). It is an active component of a large array of crucial metabolites, such as amino acids, methionine (Met) and cysteine (Cys) and many co‐enzymes, peptides (glutathione and phytochelatins), protein, sulfolipids, vitamins (biotin and thiamine) and thioredoxin system (Takahashi et al , Gotor et al , Khan et al , Jahan et al ). Adequate S supply improves the photosynthetic process and induces the growth of plants, and it also shows regulatory interaction with other important elements such as N and interacts with the process of N‐assimilation (Scherer ).…”

“…These are the chemical messengers that interrelate with nutrients synergistically or antagonistically and play an imperative role for modulating the physiological responses that lead to salt tolerance (Fatma et al 2013). Particularly, nitric oxide (NO) has emerged as an ubiquitous important free radical gaseous signaling molecule involved in plant development, various physiological functions and nutrient assimilatory processes and has also been reported to improve plant tolerance to environmental stresses including salt stress, toxic metals, low and high temperature, ultraviolet (UV)-B, ozone, excess light and various pathogens (Fatma et al 2016, Asgher et al 2017, Hasanuzzaman et al 2018, Kaya et al 2019a, 2019b. NO plays a pivotal role in alleviating the oxidative damage and improves the antioxidant defense machinery in several salt-affected plant species (Guo et al 2009, Hasanuzzaman et al 2018, Ahmad et al 2018a, 2018b.…”

“…NO plays a pivotal role in alleviating the oxidative damage and improves the antioxidant defense machinery in several salt-affected plant species (Guo et al 2009, Hasanuzzaman et al 2018, Ahmad et al 2018a, 2018b. A coordination of NO with S has been shown to strengthen the plant antioxidant machinery and thus, salt tolerance via maintaining ionic and redox homeostasis and improving photosynthetic performance and growth (Fatma et al 2016). However, the information on the role and underlying mechanism of N-S coordination with NO in plants under salt exposure is scanty.…”