Exogenous Ca2+ alleviates nitrogen and water deficit, and improves growth of wheat (Triticum aestivum) seedlings exposed to high temperature

This study was designed to examine whether exogenous Ca2+ would improve nitrogen nutrition, water status and growth of high temperature (HT)-stressed wheat (Triticum aestivum) seedlings. Wheat plants were exposed to 35/30 and 25/20A degrees C as temperature control. Some of HT-stressed plants were simultaneously treated with 4 mM Ca2+. External Ca2+ could obviously improve growth of HT-exposed wheat seedlings indicated by the biomass. Compared with Ca2+-untreated plants, total nitrogen content showed a significant increase in Ca2+-treated plants under HT stress, this primarily resulted from enhanced nitrate reductase activity and depressed loss of ammonium through photorespiration. External Ca2+ application could also increase leaf relative water content and alleviate osmotic stress via increased K+ ion and water-soluble carbohydrates in HT-stressed plants. Whereas free proline content showed remarkable decline in Ca2+-treated plants at HT stress.