Abstract:

In this study, flue-cured tobacco ‘Cuibi No.1’ was used as the material, and four concentrations of magnesium supply (0, 12.0, 48.0 and 120.0 mg/L) and two light intensities [600 and 1200 µmol/(m²·s)] at 33℃ were designed to study the effects of magnesium supply on the physiology of tobacco plants under high light intensity and high temperature stress. The results showed that: (1) the contents of sucrose and soluble sugar in the shoots and roots of tobacco plants were significantly affected by the supply of magnesium and the intensity of light, while the starch content of tobacco plants was also significantly affected by the light intensity; high light intensity could induce the accumulation of soluble sugar in the shoots and roots of tobacco plants, and the soluble sugar in the shoots reached its maximum value under high light intensity when the magnesium supply was 48.0 mg/L; (2) with the increase of magnesium supply, the activities of key enzymes in carbon and nitrogen metabolism, including sucrose synthase (SS), sucrose phosphate synthase (SPS), acid invertase (AI), glutamine synthase (GS) and nitrate reductase (NR), increased first and then decreased, and reached the maximum at 48.0 mg/L of magnesium supply; these enzyme activities in tobacco plants under high light intensity were higher than those under normal light intensity; magnesium supply, light intensity and magnesium supply × light intensity significantly affect NR and AI activities in the shoots of tobacco plants; (3) high temperature and high light intensity enhanced the absorption of K⁺ and Ca²⁺ in tobacco plants, but the absorption was inhibited with the increase of magnesium supply; magnesium supply, light intensity and magnesium supply × light intensity significantly changed the contents of K⁺ and Ca²⁺ in the roots of tobacco plants. Appropriate magnesium supply (48.0 mg/L) could enhance the activities of key enzymes of carbon and nitrogen, promote the metabolism of carbon and nitrogen, increase the accumulation of soluble sugar, and then alleviate the damage of high temperature and high light intensity to tobacco plants.

Key words: tobacco, magnesium, high temperature and strong high stress, carbon and nitrogen metabolism, carbohydrate, K⁺ and Ca²⁺