Effects of nitrogen on sweet sorghum seed germination, seedling growth and physiological traits under NaCl stress

The effects of nitrogen application on germination, seedling growth and physiological traits of sweet sorghum Sorghum bicolor (L.) Moench were investigated under NaCl stress. The aim of the study was to enhance salt-tolerance of sweet sorghum through laboratory germination experiments at different salt and nitrogen (N) concentrations using two N sources. The results showed that either salt or N significantly influenced seed germination and seedling growth of sweet sorghum. Under NaCl stress, sweet sorghum salt uptake increased via improved enzyme activities and osmoregulation during seed germination and bud seedling growth stages. Under NaCl stress, there was a little ability for sweet sorghum to resist salt by improving enzyme activity and osmoregulation substance during seed germination and seedling growth stage. Lowest root POD activity, highest leaf MDA accumulation, leaf soluble sugar and leaf POD under 100 mmol·L^-1 NaCl stress indicated the greatest salt damage to sweet sorghum. N treatments without NaCl markedly affected seed germination and seedling growth of sweet sorghum. Sweet sorghum seedling grew best under 20 mmol(N)·L^-1 due to lessening cell damage by NaCl. NH₄Cl improved more than KNO₃ in seed germination and seedling growth of sweet sorghum. Under 100 mmol·L^-1 NaCl stress, supplementation with either form of the two N sources (NH₄⁺ and NO₃^- ) ameliorated adverse salt stress effects on seedling growth and examined physiological traits. This was possible by improving POD activity and reducing MDA accumulation. It was evident that an appropriate nitrogen fertilizer application improved the salt tolerability of sweet sorghum.