Individual and Synergic Effects of Phosphorus and Gibberellic Acid on Organic Acids Exudation Pattern, Ultra-Structure of Chloroplast and Stress Response Gene Expression in Cu-Stressed Jute (Corchorus Capsularis L.)

Copper (Cu) pollution in agricultural soils is considered as a serious health risk due to its accumulation in plants. Thus, there is an urgent need to optimize nutrient application for higher yield with lower Cu uptake to ensure food security. A pot experiment was conducted to determine the effects of single and/or combined application of different levels (0 and 80 kg ha−1) of phosphorus (P) and gibberellic acid (0 and 100 mg L−1) on Cu accumulation, morpho-physiological and antioxidative defence attributes of jute (Corchorus capsularis L.) exposed to severe Cu stress (0, 200 and 400 mg kg−1). Results revealed that C. capsularis tolerated up to 200 mg kg−1 Cu concentration without a significant (P < 0.05) decrease in biomass, plant height and root length but further increase in Cu concentration from 400 mg kg−1 exhibited a significant reduction in plant height, root length, stem fresh weight, stem dry weight, plant fresh weight and plant dry weight. Although increasing levels of Cu in the soil caused a significant (P < 0.05) decrease in photosynthetic pigments, gas-exchange characteristics, fibre yield and quality, essential nutrients in different parts of the plants, disturbance in ultrastructural organelles (especially chloroplast) and increased the contents of Cu in roots, leaves, stems and fibres. However, Cu toxicity boosted the production of reactive oxygen species (ROS) by increasing the contents of malondialdehyde (MDA), which is the indication of oxidative stress in C. capsularis plants and was also manifested by hydrogen peroxide (H2O2) contents and electrolyte leakage to the membrane bounded organelles and ROS generation is scavenged by the various enzymatic and non-enzymatic antioxidants. In addition, the contents of organic acids were also increased with the increasing levels of Cu in the soil. The negative impacts of Cu injury were reduced by the application of P and GA3 which increased plant growth and biomass, improved photosynthetic apparatus, fibre yield and quality, antioxidant enzymes, minerals uptake together with diminished exudation of organic acids as well as oxidative stress indicators in roots of C. capsularis by decreasing Cu toxicity. Moreover, the phytoremediation potential of fibrous C. capsularis can also be increased by the application of P and GA3. Here, we conclude that the application of P and GA3 under the exposure of Cu stress significantly improved plant growth and biomass, photosynthetic pigments, gas-exchange characteristics, regulate antioxidant defence system and essential nutrients uptake and maintained the ultra-structure of membranous bounded organelles in C. capsularis. Graphical Abstract: [Figure not available: see fulltext.].