Effects of Density, Leaf Number Remained and Their Interaction on Photosynthetic and Economic Characters of Flue-Cured Tobacco

A field experiment was conducted using two-factor randomized complete block design to investigate the effects of density (D), number of leaves remained (L) and their interaction on photosynthetic characters and economic traits of flue-cured tobacco (cv Yunyan 97). The results showed that D, L and their interaction had significant effects on photosynthetic characters and economic traits of flue-cured tobacco, and the responses from the D were greater than those from L and their interaction. Under same L condition, Pn, Gs, Ci, Tr and chlorophyll content increased first and then declined as D increased. As for the low and medium D conditions, with L increasing, Pn, Gs, Ci, Tr and chlorophyll content increased gradually, but they increased first, and decreased later under high D conditions. In addition, light and CO₂ response curve type from all treatments were the same, but response curve parameters were different. With L increasing, maximum Pn rised gradually under low and medium D conditions, while increased first, and decreased later under high conditions. With L increasing, both yield and output value increased significantly under seam D conditions; under seam Lconditions, yield rised gradually, but output value increased firstly and then declined, when D increased. On the consideration of comprehensive analysis, effect of 16500/23 treatment was best; and theoretically the appropriate D and L for Yunyan 97 were 17093-17665 plant/ha and 21.3-23.1 leaves/plant respectively.