Differential responses of exogenous melatonin on growth, photosynthesis and antioxidant defence system in two Brassica napus L.cultivars under chromium stress

Abstract

Rapid industrialization throughout the world during last few decades causing high chromium resulted widespread of agricultural soil contamination. The increased chromium contents beyond permissible level in some agricultural land areas increasing widespread concern about food safety.This study was carried out for evaluation of metal toxicity damage and its possible mitigation and improved photosynthetic efficiency by melatonin treatment in canola plants exposed to four melatonin levels (0,1,5,10µM) treated with chromium stress (0,50,100µM) for two days.Chlorophyll fluorescence a transients considered one of the best tool for photosynthetic (photosystem II) efficiency analysis of two canola cultivars Ac-Excel and DGL with or without melatonin treatment against chromium stress analyzed by using OJIP test (at different time scale) chromium treated and non-treated plants. Enhanced ROS scavenging antioxidants enzymes (SOD, POD, APX,CAT) and H2O2, MD Aactivity photo synthetic efficiency was observed against chromium stress. DGL cultivar showed greatly affected and showed maximum reduction in performing index of photosystem II and yield for primary photochemistry as compared to chromium treated and non-treated plants as compared to Ac-Excel. Performing index primarily comprises of active number of reaction centers as per absorption, primary photochemistry yield and efficiency of electron transfer in electron transport chain activities were observed high in Ac-Excel cultivar. However exogenous application of melatonin protected the oxygen evolving complex of PSII and helped out in maintaining PSII activity. Thus OJIP fluorescence transients are quite helpful for understanding the intersystem electron transport beyond photosystem II response of canola cultivars in chromium stress. Findings: Exogenous application of Melatonin can improve plant growth and development in heavy metalstress by modulation of photosynthesis in terms of enhanced photosystem II efficiency and redox potential in certain environmental stress conditions.

Mitigation of Negative Effects of Chromium (VI) Toxicity in Faba Bean (Vicia faba) Plants through the Supplementation of Kinetin (KN) and Gibberellic Acid (GA3)

“…Under severe environmental perturbations, chlorophyll fluorescence is extensively implied to enumerate stress tolerance and acclimation in plants [ 72 ]. During the present study, a significant decrease was observed in the Fv/Fm, ΦPSII, and qP under Cr stress, and these results are consistent with those reported in Wheat [ 73 ], Tomato, and Brassica napas [ 39 ]. Impaired PSII electron flow under Cr stress can cause photo-inhibition that enhances the obliteration in antenna molecules [ 74 , 75 ].…”

“…In agreement with our results, several recent studies have also documented a decline in growth and biomass in different plants such as Brassicca napus , wheat, and Arabidopsis under Cr stress [ 35 , 36 , 37 ]. The reduction in plant growth by Cr phyto-toxicity has been suggested to result from the degradation of chlorophyll pigments [ 38 , 39 ], disturbed nutrient uptake balance [ 33 ], ROS overproduction, destruction of cellular ultrastructure [ 40 ], and disorganization in antioxidant defense machinery [ 33 ]. Hence, it is a prerequisite to improve the Cr stress tolerance in faba bean to avoid its negative effect on plant growth.…”

“…Impaired PSII electron flow under Cr stress can cause photo-inhibition that enhances the obliteration in antenna molecules [ 74 , 75 ]. Electron transport from the primary to secondary acceptor is blocked at the PSII acceptor side that drastically reduces the ratio Fv/Fm [ 39 , 76 ]. Negative effects on various photosynthetic parameters such as ΦPSII, qP, Fv/Fm ratio, and NPQ were reversed when Cr-stressed faba bean plants were treated with GA3 and kinetin alone or in combination.…”

Melatonin Modulates Plant Tolerance to Heavy Metal Stress: Morphological Responses to Molecular Mechanisms

“…Moreover, MT treatment increased Bermuda grass’ resistance to Pb stress [ 95 ]. External MT treatment to Brassica napus (canola) enhanced growth traits under Cr stress through higher PS II efficiency and photosynthetic quotient (PQ) redox rate [ 85 ]. Application of MT in Cr-stressed Origanum majorana plants preserved higher levels of photosynthetic pigments and less ROS by stimulating the antioxidant machinery and osmotic balance, decreased lipid peroxidation, and improved cellular membrane integrity [ 77 ].…”

ROS and NO Phytomelatonin-Induced Signaling Mechanisms Under Metal Toxicity in Plants: A Review

“…Pers.) [128] maize (Z. mays L.) [120] Ulva (green macroalga) [141] Cd mallow (Malva parviflora, Malvaceae) [49] Spinacia oleracea L. [142] strawberries (Fragaria × ananassa) [81] alfalfa [130] tomato [131][132][133] wheat [124,134] Cyphomandra betacea [135] Malachium aquaticum [136] Galinsoga parviflora [136] Perilla frutescens [137] rice [138,139] Ulva [140,141] rapeseed (Brassica napus) [48] cucumber (Cucumis sativus L.) [95] Cu cucumber (Cucumis sativus L.) [100] melon (Cucumis melo L.) [45] Zn Ulva (green macroalga) [141] wheat (Triticum aestivum L.) [143] safflower (Carthamus tinctorius L.) [53] Al soybean (Glycine max L.) [148] wheat [149] rapeseed (Brassica napus) [48] V watermelon (Citrullus lanatus) [50] Ni tomato (S. lycopersicum L.) [144] Cr wheat (Triticum aestivum L.) [145] canola (Brassica napus L.) [147] B wheat (Triticum aestivum ) [30] As rosemary (Rosmarinus officinalis L.) [150] rice (Oryza sativa L.) [41,51] AsA-GSH cycle Pb bermudagrass (Cynodon dactylon L.) [128] maize (Z. mays L.) [120] Ulva (green macroalga)…”