温度变化对烟草光合作用光响应特征的影响

通过Li-6400光合测定系统控温,研究了大田条件下,烟草脚叶采烤期腰叶在17、20、25、30和35℃下的光合作用光响应特征。结果表明:随温度升高,净光合速率(Pn)、最大净光合速率(Pnmax)、初始斜率(α)和气孔导度(Gs)先上升后下降,在20℃下达最大值,35℃下净光合速率受强光的抑制作用明显;光补偿点(LCP)和暗呼吸速率(Rd)随温度升高而上升,但35℃下二者较30℃时有所下降;光饱和点(LSP)随温度升高而呈下降-上升-下降的变化,30℃和17℃时LSP较高;蒸腾速率(Tr)随温度上升而增强,水分利用效率(WUE)则随温度升高而下降,但20℃时水分利用效率在强光下明显较其他温度下的高。结果说明,20℃最适合烟草光合作用,此温度下气孔的水、气调节能力最强,温度高于30℃则对烟草光合作用不利。

Effects of temperature variation on the light-response characteristics of tobacco leaf photosynthesis

By using Li-6400 photosynthesis determination system to control leaf chamber temperature, this paper studied the photosynthetic light-response characteristics of middle tobacco leaves at their initial ripening stage at 17, 20, 25, 30, and 35 ℃. With increasing temperature, the net photosynthetic rate (Pn), maximum net photosynthetic rate (Pnmax), initial slope (α), and stomatal conductance (Gs) decreased after an initial increase, with the maximum at 20 ℃, while the Pn was inhibited obviously at 35 ℃ by strong light. The light compensation point (LCP) and dark respiration rate (Rd) increased with increasing temperature, but decreased slightly at 35 ℃, as compared with those at 30 ℃. The light saturation point (LSP) had a variation of ‘down-up-down’ with increasing temperature, being higher at 35 ℃ and 17 ℃. The transpiration rate (Tr) increased but the water use efficiency (WUE) decreased with increasing temperature. However, WUE was higher at 20 ℃ than that at the other temperatures under strong light. It was suggested that the most favorite temperature for tobacco photosynthesis was 20 ℃, at which, the water- and gas regulation capability of stomata was the strongest. High temperature over 30 ℃ would work against tobacco photosynthesis.