Differential Response of Salt-Sensitive and Salt-Tolerant Brassica juncea L. Genotypes to N Application: Enhancement of N-Metabolism and Anti-Oxidative Properties in the Salt-Tolerant Type

摘要

Different strategies in response to the application of nutrients are required to overcome the adverse effects of NaCl stress. The objective of the present study was to determine if different added levels of nitrogen (N) in growth medium could alleviate the adverse effects of salt stress on plant N-metabolism and the antioxidative system. Two-week-old plants of salt-sensitive (cv. 'Chuutki') and salt-tolerant (cv. 'Radha') genotypes of Brassica juncea L. Czem. & Coss. were treated with: (i) 0 mM NaCl+ 0 mg N kg~(-1) sand (control), (ii) 90 mM NaCl +30 mg N kg~(-1) sand, (iii) 90 mM NaCl + 60 mg N kg~(-1) sand, (iv) 90 mM NaCl + 90 mg N kg~(-1) sand and (v) 90 mM NaCl + 120 mg N kg~(-1) sand. Under salinity stress, the salt-tolerant genotype exhibited maximum value for growth attributes [shoot length (SL) plant~(-1), area (A) lear~(-1), and leaf area index (LAI)], sulphur assimilation enzyme [ATP-sulphurylase (ATP-S)], N-assimilation enzymes [nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS) and glutamate synthase (GOGAT)], and antioxidative enzymes [superoxide dismutase (SOD), ascorbate peroxidise (APX) and glutathione reductase (GR)] and content of antioxidant [glutathione (GSH) and ascorbate (ASC)] at 60 mg N kg~(-1) sand than the salt-sensitive genotype. These results suggest that the salt-tolerant genotype may have better N-metabolism, antioxidative system and protection from reactive oxygen species (ROS) with N application under salt stress.