减弱UV-B辐射对烟草形态、光合及生理生化特性的影响

在地处低纬高原云南较高海拔烟区的通海县大田条件下,通过大棚覆盖不同透明膜的方式梯度减弱UV-B辐射,研究了外界环境30.39%(T1)、70.08%(T2)和75.74%(T3)强度的UV-B辐射对烟草品种K326形态、光响应特性和部分生理生化特征的影响。结果显示:减弱UV-B辐射促进了K326节间距和茎高的伸长,使叶片增大、变薄,尤以T2处理植株的叶片、茎围和节间距最大,而K326发育进程由T1至T3逐渐加快。在减弱UV-B辐射下,K326净光合速率(Pn)、最大净光合速率(Amax)和蒸腾速率(Tr)较高,但水分利用效率(WUE)、暗呼吸速率(Rd)、光补偿点(LCP)和光饱和点(LSP)较低。其中T1的Rd和LCP最低,并极大地降低了表观量子效率(AQY),T2的LSP最低而Pn最高,而T3的Amax、LCP和AQY最高。减弱UV-B辐射后烟叶叶绿素含量提高,而类黄酮、比叶重、类胡萝卜素含量和面积含水量下降,鲜重含水量和自然水分饱和亏却上升;T3处理下丙二醛含量最大,鲜重含水量和自然水分饱和亏则T2最大。结果表明,适当高强度的UV-B辐射对促进K326正常生长发育和提高其对UV-B辐射的适应性有重要作用。

Effects of reduced ultraviolet-B radiation on morphology, photosynthesis and some other physiological and biochemical characteristics in tobacco

High quality tobacco producing area of Yunnan Province of China, in which the solar UV-B radiation is significant higher than low-altitude plains and hills, is mainly distributed between 1000 m and 2000 m above sea level (a.s.l.). UV-B radiation had significant effects on growth, self-protection and secondary metabolism of tobacco (Nicotiana tabacum L), and UV-B-exclusion experiment provides a good method for examining the effects of diverse UV-B radiations from zero to natural ambient level on plant. In order to understand the effects of solar UV-B radiation on morphology, photo-response characteristics and other physiological and biochemical characteristics in Nicotiana tabacum L. in Yunnan areas with geographical characteristics of low latitude plateau, tobacco cultivar K326 was selected and planted under 30.39% (T1), 70.08% (T2) and 75.74% (T3) of current UV-B radiations by covering different UV transparent membranes above canopy in field of Tonghai, Yunnan (1806 m a.s.l.), and the resulting changes of tobacco upon different reduced UV-B treatments were further analyzed. The results showed as follows. Reduced UV-B radiations promoted elongation of internode length and stem length, increased leaf size and thinned blades. The maximum leaf size, stem girth and internode length were observed in T2, and development process of K326 gradually accelerated from T1 to T3. Under reduced UV-B conditions, net photosynthetic rate (Pn), maximum net photosynthetic rate (Amax) and transpiration rate (Tr) increased, while water utilizing efficiency (WUE), dark respiration rate (Rd), light compensation point (LCP) and light saturation point (LSP) reduced. Comparison of the three reduced UV-B radiation treatments, the lowest Rd and LCP were observed in T1, in which the apparent quantum yield (AQY) was greatly reduced as well. LSP in T2 was far below the other treatments, while Amax, LCP and AQY were the highest in T3 among the three treatments. Reduced UV-B radiations increased chlorophyll concentration, leaf fresh weight water content and natural water saturation deficit, but reduced carotenoid, specific leaf mass (SLM), water content per unit of leaf area and flavonoid contents. In the three reduced UV-B treatments, the maximum point of malonaldehyde (MDA) content in tobacco K326 was found in T3 and the maximum points of leaf fresh weight water content and natural water saturation deficit were found in T2. These results suggested that a certain intensity range of UV-B radiation would be favorable for development and increasing the adaptability to UV-B radiation of tobacco cultivar K326. And cultivar K326 has a strong ability to adapt the current high intensity of solar UV-B radiation in Tonghai through morphological and physiological changes, such as photosynthetic characteristics, defense mechanism and leaf water state etc.