Effects of Light Intensity on Quality of Tobacco Seedlings in Floating System

The effects of light intensity on agronomic characteristics of tobacco seedlings were studied under shield of white gauze.The results showed that with the decrease of light intensity, the height of seedlings increased, while the stem circumference, leaf thickness, specific leaf weight, ratio of dry weight to fresh weight and matter accumulation of seedlings reduced;the root systems of seedlings were not well developed, root system vitality lowered and the ratio of root to shoot decreased;the moisture content of tobacco seedlings was also affected, the free water content was increased and bound water content was decreased by shading;the contents of chlorophyll, total nitrogen and protein and NR activity in tobacco seedlings increased, however, the value of Chla/Chlb, INV activity and contents of total sugar and nicotine decreased.It indicated that the quality of tobacco seedlings declined with the decrease of light intensity under the conditions of 4 light intensities set in this experiment.