Effects of artificial shading on growth, development and photosynthetic characteristics of different varieties of flue-cured tobacco

In order to investigate the effects of light stress on the early flowering of flue-cured tobacco, the effects of artificial shading on the growth, development and photosynthetic characteristics of flue-cured tobacco cv. K326 and anti-early flowering flue-cured tobacco line HY06 were studied via field experiments. The results showed that after growing under 44% of natural light intensity for 30 days, 1) the growth of flue-cured tobacco was significantly influenced by shading. The plant height and stalk circumference of the two varieties decreased significantly, although the plant height of HY06 was taller; 2) the flower budding of the flue-cured tobacco was significantly affected by the shading treatment. The number of effective leaves at the budding stage of the two varieties were reduced remarkably, with HY06 displayed more than the other variety; the flower budding stage was also delayed; 3) shading significantly decreased the net photosynthetic rate, stomatal conductance and photosynthetic oxygen evolution rate of the tobacco leaves and significantly increased intercellular CO₂ concentration. The contents of chlorophyll and carotenoid, net photosynthetic rate and chlorophyll b synthesizing capability of HY06 were higher than those of K326. These results indicate that new anti-early flowering line HY06 possesses a better adaptability for weak light.