Effects of selenium on the growth and photosynthetic characteristics of flue-cured tobacco (Nicotiana tabacum L.)

The objective of this study was to investigate the effect of Selenium (Se) supply (0, 3, 6, 12, 24 mg kg(-1)) on the growth, photosynthetic characteristics, Se accumulation and distribution of flue-cured tobacco (Nicotiana tabacum L.). Results showed that low-dose Se treatments (<= 6 mg kg(-1)) stimulated plant growth but high-dose Se treatments (>= 12 mg kg(-1)) hindered plant growth. Optimal Se dose (6 mg kg(-1)) stimulated plant growth by reducing MDA content and improving photosynthetic capability. However, excess Se (24 mg kg(-1)) increased MDA content by 28%, decreased net photosynthetic rate and carboxylation efficiency by 34% and 39%, respectively. The Se concentration in the roots, stems, and leaves of the tobacco plants significantly increased with increasing Se application. A linear correlation (R = 0.95, P < 0.01) was observed between Se level and tobacco plant tissue Se concentration. This correlation indicated that the tobacco plant tissues were not saturated within the concentration range tested. The pattern of total Se concentration in the tobacco plant tissues followed the order root > leaf > stem. The Se concentration in the roots was 3.17 and 7.57 times higher than that in the leaves and stems, respectively, after treatment with 24 mg kg(-1) Se. In conclusion, the present study suggested that optimal Se dose (6 mg kg(-1)) improved the plant growth mainly by enhancing photosynthesis, stomatal conductance, carboxylation efficiency and Rubisco content in the flue-cured tobacco leaves. However, the inhibition of excess Se on tobacco growth might be due to high accumulation of Se in roots and the damage of photosynthesis in leaves.