Relationships between tobacco leaf δ¹³C and physiological characteristics

In this paper, the flue-cured tobacco K326 was employed to study the abundance of carbon isotope composition, photosynthetic pigment content, soluble protein content and leaf mass per area (LMA) of tobacco leaf which were grown at four testing sites of different altitude (T₁, T₂, T₃, T₄). The correlations of carbon isotope composition with altitude, leaf position and physiological measures were understood as well. Results showed that δ¹³C of those samples varied from -27.4‰ to -23.4‰. The δ¹³C of samples from T₁, T₂and T₃ were increased with rising of the leaf position. δ¹³C of middle and upper leaves from T₁, T₂and T₃ were positively correlated with altitude. However, δ¹³C of samples from T₄ ranging from -26.8‰ to -26.4‰ was lower than the values from previous samples. The δ¹³C also decreased with the increasing of leaf position, and was significantly negatively correlated with chlorophyll content and chlorophyll/carotinoid ratio (P < 0.05). The δ¹³C was not significantly correlated with carotinoid content and chlorophyll a/b ratio. Meanwhile, it was positively correlated with soluble protein content and LMA significantly (P < 0.01). Generally, our findings indicated that chlorophyll content, chlorophyll/carotenoid ratio, soluble protein content, and LMA had strong relationships with δ¹³C, whereas the relationship of δ¹³C with altitude and leaf position was still unclear. (authors)