Effects of magnesium on tobacco growth and chlorophyll fluorescence parameters of tobacco leaves

This study focused on the changes of tobacco growth, chlorophyll content and chlorophyll fluorescence of tobacco leaves under different concentration of magnesium supplementation (Mg2+ 0, 0.5, 1, 2, 4, 8, 16 mmol/L) using solution culture, and the results provide the theoretical foundation for rational application of magnesium fertilizer and high quality culture of tobacco. The results showed that application of Mg increased dry matter accumulation of flue-cured tobacco, with the concentration of Mg2+ 2–4 mmol/L having the highest effect. Neither too high nor too low concentration of Mg had any beneficial effect on the growth of flue-cured tobacco. Leaf chlorophyll content was increased first but decreased when the Mg2+ concentration was 2mmol/L. Chlorophyll content of tobacco leaves was decreased significantly under either Mg2+-deficient or Mg2+-excessive conditions. The effective quantum yield (EQY), electron transport rate (ETR) and non-photochemical quenching (NPQ) were all the highest at the concentration of 8 mmol/L Mg2+. Tobacco leaves had the largest adaptability to high light intensity at the concentration of 8 mmol/L Mg2+. Both Mg2+-excessive and Mg2+-deficient conditions decreased the effective quantum yield, suffocated the electron photosynthetic rate and reduced the dissipation of excessive excitation energy.