Characteristics of Injury and Recovery of Net NO3− Transport of Barley Seedlings from Treatments of NaCl

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Abstract
The nature of the injury and recovery of nitrate uptake (net uptake) from NaCl stress in young barley (Hordeum vulgare L, var CM 72) seedlings was investigated. Nitrate uptake was inhibited rapidly by NaCl, within 1 minute after exposure to 200 millimolar NaCl. The duration of exposure to saline conditions determined the time of recovery of NO3− uptake from NaCl stress. Recovery was dependent on the presence of NO3− and was inhibited by cycloheximide, 6-methylpurine, and cerulenin, respective inhibitors of protein, RNA, and sterol/fatty acid synthesis. These inhibitors also prevented the induction of the NO3− uptake system in uninduced seedlings. Uninduced seedlings exhibited endogenous NO3− transport activity that appeared to be constitutive. This constitutive activity was also inhibited by NaCl. Recovery of constitutive NO3− uptake did not require the presence of NO3−.