增强UV-B辐射对高山植物麻花艽净光合速率的影响

EFFECTS OF SUPPLEMENTARY UV-B RADIATION ON NET PHOTOSYNTHETIC RATE IN THE ALPINE PLANT GENTIANA STRAMINEA

在高寒矮嵩草 (K obresia humilis)草甸地区以太阳短波辐射为背景 ,建立了人工增强 U V- B辐射的实验装置 ,每天增补 15 .8k J· m- 2 的辐射剂量 ,模拟平流层臭氧破坏约 5 %时近地表面太阳 UV- B辐射的增强。观测表明 :UV- B辐射的增强对麻花艽 (Gentiana straminea)植物的光合作用无明显的抑制或伤害作用。相反 ,在早晨补充UV- B辐射的短时间内 ,叶片的 Pn 随 Gs的增大而有所提高。随 UV- B辐射时间的延长 ,约在 11∶ 30～ 12∶ 30 ,Pn和Gs有所降低。U V- B辐射时间进一步延长后 (约 14∶ 0 0以后 ) ,处理和对照组叶片 Pn和 Gs的差异趋向不明显。增强太阳 UV- B辐射后 ,麻花艽叶片的光合色素并无明显变化 ,U V- B吸收物质的含量也无明显变化。麻花艽叶片厚度的直接测量表明 :增强 U V- B辐射能明显提高叶片的厚度。叶片厚度的增加可补偿增强 U V- B辐射后引起的光合色素的光降解 ,改善单位叶面积为基础的光合速率 ,是高原植物对强 U V- B辐射的一种适应方式。

Field experiments of enhanced UV-B radiation on plant photosynthesis were conducted in a Kobresia humilis meadow at the Haibei Alpine Meadow Ecosystem Research Station (37°29′-37°45′ N,101°12′-101°33′E; Alt.3200 m). The total daily exposure in treatments was 158 kJ·m -2, stimulating a 5% ozone depletion in this region The field experiment indicated that there was no deleterious effect of UV-B radiation on P_n of Gentiana straminea With one hour of irradiation,P_n increased with increasing G_s From 11∶30 to 12∶30,there was a depletion of P_n and G_s,and after 14∶00,there was no obvious influence on either P_n or G_s There were no changes in photosynthetic pigment content or UV-B-absorbing compounds after the enhancement of UV-B radiation All these may result from the increased thickness of G straminea leaves,which could compensate for the photolysis of photosynthetic pigments,and also from the high concentration of UV-B-absorbing compounds which occur mainly in the leaf epidermis