Meja and GABA up-regulate growth and PS II photochemistry in brinjal and tomato seedlings exposed to cadmium toxicity

Cadmium (Cd) toxicity has become a significant threat to crop productivity, and vegetables appear to be at substantial risk. In the present study, the potential of methyl jasmonate (MeJA, 0.015 µM) and gamma-aminobutyric acid (GABA 15 µM) was explored to alleviate the Cd toxicity (12 µM) in tomato and brinjal seedlings. Cd declined fresh and dry mass by 21% and 18% in tomato seedlings and 27% and 25% in brinjal seedlings. Cd significantly damages pigment contents (Chl a, Chl b, and Car), PS II photochemistry (Chl fluorescence kinetics), and photosynthetic gas exchange parameters in both seedlings. Furthermore, Cd exacerbates oxidative biomarkers despite the enhanced activity of antioxidant enzymes CAT, SOD, POD, and GST in both seedlings. Plant growth regulators GABA and MeJA application to seedlings led to a significant decline in Cd uptake and oxidative biomarkers content and up-regulation of antioxidative enzymes activity, leaves gas exchange parameters, photosynthetic performance, and seedlings growth parameters. Additionally, biosynthetic inhibitors diethyldithiocarbamate acid (DIECA) of MeJA and 3-Mercaptopropionic acid (MPA) of GABA further raised Cd uptake, thereby, excessive increase in oxidative biomarkers worsened Cd toxicity on photosynthesis. Hence, growth was significantly reduced. Thus, the study concludes that as compared to brinjal seedlings, tomato showed greater tolerance to Cd toxicity, and GABA plays a crucial role in mitigating the Cd toxicity; however, GABA and MeJA together more efficiently alleviated the toxicity.