光强和氮素对紫茎幼苗光合特性的影响

【目的】研究紫茎 Stewartia sinensis 幼苗对不同光强和土壤氮素质量分数的光合生理生态适应差异性，筛选紫茎幼苗适宜的光强和氮素处理组合。【方法】选择 1 年生紫茎幼苗为试验材料，设置 4 个透光率分别为全光 100.00%(L₀)、轻度遮光 (44.79 ± 0.51)%(L1)、中度遮光 (19.60 ± 0.23)%(L2)、高度遮光 (7.25 ± 0.10)%(L3),3 个施氮量分别为低氮 0.2 g·kg-1(N1)、高氮 0.6 g·kg_-1 (N₂) 和不施氮 (N₀)，经 90 d 处理测定不同光、氮处理下紫茎幼苗的光响应过程、光合色素质量分数和叶绿素荧光参数。【结果】光强、氮素及其交互作用对紫茎幼苗的光合色素质量分数和叶绿素荧光参数的影响均达显著水平 (P<0.05)。紫茎幼苗的叶绿素 a/b 为 2.0～2.5，光补偿点 (LC_P) 为 4.8～26.0 μmol·m^-2·s^-1，光饱和点 ...

Effects of light intensity and nitrogen treatments on photosynthetic characteristics of Stewartia sinensis seedlings

  Objective  This study, with an investigation of the differences in the hotosynthetic hysiological and ecological adaptation of Stewartia sinensis seedlings to different light intensity and soil nitrogen content, is aimed to select combinations of light intensity and nitrogen treatment that are conducive to the cultivation of S. sinensis seedlings.   Method  With S. sinensis seedlings used as test materials, efforts were made to set four light intensity gradients, namely full light (L₀), light light (44.79±0.51)% (L₁), moderate light (19.60±0.23)% (L₂), high light (7.25±0.10)% (L₃), and three nitrogen application rates, i.e, low nitrogen 0.2 g·kg?1 (N₁), high nitrogen 0.6 g·kg?1 (N₂) and no nitrogen application (N₀) before the light response process, photosynthetic pigment mass fraction and chlorophyll fluorescence parameters were recorded and measured upon 90 d treatment.   Result   Light intensity, nitrogen and their interaction displayed significant effects on photosynthetic pigment and chlorophyll fluorescence of S. sinensis seedlings (P＜0.05). Chl a/b values of S. sinensis seedlings varied from 2.0 to 2.5, the L_SP of S. sinensis seedlings varied from 571.3 to 931.4 μmol·m?2·s?1 whereas L_CP varied from 4.8 to 26.0 μmol·m?2·s?1. With the increase of shading degree, the Chl, Car, F_o, F_m, A_QY of S. sinensis seedlings tended to increase, the Chl a/b and Car/Chl tended to decrease while the P_max, F_v/F_o, F_v/F_m and P_IABS increased first and then decreased. With the increase of nitrogen application rate, the P_IABS of S. sinensis seedlings tended to increase, the Chl a/b, F_o and F_m tended to decrease and the Chl, Car, P_max and A_QY increased first and then decreased; With L₁ and L₂ light intensity, P_n, G_s and T_r of S. sinensis seedlings were higher and C_i was lower and the application of low nitrogen significantly promoted P_n, G_s and T_r. The P_max of L₁N₁ increased by 45.21% compared with L₁N₀ with the P_n and P_max of L₂N₁ being the highest.   Conclusion  S. sinensis seedlings had the best photosynthetic capacity when grown with moderate shading and low nitrogen treatment whereas photosynthetic inhibition occurred with full light or high nitrogen treatment. [Ch, 1 fig. 6 tab. 34 ref.]