Effect of Shading on Growth and Photosynthetic Characteristics of Cigars

Purpose To investigate the effects of different shading intensities on the growth, development, and photosynthetic characteristics of ND-2 cigar wrapper.

Methods Four shading treatments (S₁: 60 mesh shading net, S₂: 80 mesh shading net, S₃: 100 mesh shading net, CK: no shading) were set up in field experiments, and the growth, photosynthetic characteristics, relative chlorophyll content, chlorophyll fluorescence parameter characteristics, and response mechanisms of cigar under different shading intensities were studied.

Results As the shading intensity increases, the height, maximum leaf length, and maximum leaf width of cigar plants showed varying degrees of increase. Under shading treatment, the transpiration rate (T_r), intercellular CO₂ concentration (C_i), net photosynthetic rate (P_n), and stomatal conductance (G_s) of cigar tobacco leaves showed a significant upward trend, and the various photosynthetic characteristics of cigar wrapper leaves were effectively improved. The apparent quantum efficiency and maximum net photosynthetic rate (P_nmax) of cigar tobacco leaves increased with the increase of shading intensity, while the light compensation point (LCP) and light saturation point (LSP) decreased accordingly. Shading led to an increase in the relative chlorophyll content, the maximum light energy utilization efficiency of PSⅡ, potential PSⅡ activity, and actual PSⅡ photosynthetic efficiency of cigar tobacco leaves.

Conclusion Shading can reduce the LSP and LCP of cigar tobacco leaves, increase P_nmax, and adapt to low light environments; and also can improve the P_n, G_s, C_i, and T_r of leaves, enhance the photosynthetic production capacity of leaves, improve light energy utilization efficiency, enhance the adaptability of tobacco leaves to low light environments, and promote the growth and development of tobacco leaves.