Nitrogen ameliorates NaCl toxicity in eggplant seedlings: Role of hydrogen sulphide and sulphur metabolic signaling

This study investigates physiological and biochemical adaptation of eggplant (Solanum melongena L.) seedlings to sodium chloride (NaCl₀: 0.0 g NaCl kg⁻¹ sand, NaCl₁: 0.3 g NaCl kg⁻¹ sand and NaCl₂: 0.5 g NaCl kg⁻¹ sand) by varied levels of nitrogen (N): deprived N (N₀; 0 mg kg⁻¹ sand), low nitrogen (LN; 105 mg N kg⁻¹ sand), medium nitrogen (MN; 210 mg N kg⁻¹ sand) and high nitrogen (HN; 270 mg N kg⁻¹ sand) supplementation. Sodium chloride at both doses (MN + NaCl₁ and MN + NaCl₂) caused considerable decrease in growth (10 and 14 % in FW and 16 and 21 % in DW, respectively), pigments, photosynthetic oxygen evolution, PSII photochemistry and nutrient contents as compared to control (MN + NaCl₀), while HN supplementation significantly alleviated NaCl toxicity. Under similar treatment, stimulatory effect occurred on sulphur cycle enzymes adenosine triphosphate sulphurylase and o-acetylserine(thiol)lyase and metabolites glutathione and cysteine. NaCl stress induced impact was more severe in LN and N₀ (deprived N) treated seedlings, while HN supplementation protected against damage by up-regulating antioxidant system and components of S cycle. Growth showed negative correlation with Na⁺ accumulation. Nitrogen supplementation could be a potential method to minimize NaCl toxicity in eggplants by up-regulating endogenous H₂S and S metabolites. Further, non-metric-multidimensional scaling provided strong support to represent a spatial model in different variables. This technique is cost effective and covers holistic approach to propose number of agricultural and biotechnological means for sustainable agriculture and human welfare in turn.