Changes of nitrogen metabolism in millet at elevated temperatures

Abstract

Protein, products of protein degradation (ammonia- and amide-N) and glutamine synthetase (GS) activity were measured in pearl millet with or without presowing hardening to drought, and in oat, which is more sensitive than millet to drought and heat stress. It was hypothesized that millet, particularly after hardening, would be tolerant to heat stress due to enhanced GS activity promoting binding of the ammonia accumulated during exposure to high (42°C) temperature. This was confirmed: the GS activity (on a fresh weight basis) remained high in roots of millet whereas enzyme activity declined in oat. Presowing hardening raised plant tolerance to overheating and dehydration. Millet plants subjected to presowing hardening retained a higher water-soluble protein level in leaves and accumulated lower amounts of amide-N at overheating.