滤除自然光中UV-B辐射成分对高山植物美丽风毛菊光合生理的影响

doi:10.3724/SP.J.1258.2011.00176

摘要/Abstract

摘要：

采用滤除自然光谱中UV-B辐射成分的方法, 探讨了高山植物美丽风毛菊(Saussurea superba)光合机构对青藏高原强UV-B辐射的响应和适应特性。结果表明, 强太阳光中的UV-B成分能引起净光合速率的降低。连续16天不同天气下的观测表明, 滤除UV-B处理时3 min暗适应的光化学量子效率有升高的趋势; 晴天下稳态光化学效率的分析也显示滤除UV-B处理的实际光化学量子效率和光化学猝灭系数有升高趋势, 意味着自然光中的UV-B成分可限制美丽风毛菊叶片PSII反应中心的激发能捕获效率。PSII有效光化学量子效率的增加和非光化学猝灭系数的降低进一步表明, UV-B辐射能导致有效光化学效率的降低和非光化学能量耗散的增加。由上可知, 自然强UV-B辐射是限制美丽风毛菊叶片光合作用的一个因素。滤除UV-B辐射处理对光合色素含量的影响较小, 无论以叶面积还是叶鲜重为基础的滤除UV-B处理仅有微弱的增加趋势, 说明强UV-B辐射具有加速光合色素的光氧化进程, 促进细胞成熟和叶片衰亡的潜在作用。同样UV-B吸收物质的含量也几乎没有变化, 表明强太阳辐射环境下生活的高山植物美丽风毛菊叶表皮层中已具有较多的紫外线屏蔽物质, 足以抵御目前环境中强太阳UV-B辐射可能引起的伤害, 较少受UV-B辐射波动的影响。

关键词: 高山植物, 叶绿素荧光, 光化学效率, 青藏高原, UV-B辐射

Abstract:

Aims In the Qinghai-Tibet area, high levels of UV-B radiation reach the earth’s surface as part of strong solar radiation. It is therefore important to examine the response and adaptation of native alpine plants to strong UV-B radiation. Our objective was to determine the physiological response of the photosynthetic apparatus to current ambient UV-B intensity.
Methods UV-B-exclusion experiments were conducted on a field site with UV-B-excluding and UV-B-transmitting filters. The two filters transmitted similar levels of photosynthetically active radiation, and there were no differences in air temperature and relative humidity under these metal-frame suspended plastic filters. The experiments were performed in alpine Kobresia humilis meadow with the native alpine species Saussurea superba. Pulse-modulated in vivo chlorophyll fluorescence was mainly used to obtain rapid information on UV-B effects on photosynthetic processes. The trials lasted 15 or 16 days during the growing season of July and August in 2008 and 2009. We measured the 3-min dark-adapted quantum efficiency of PSII photochemistry (F_(v)/F_(m)), PSII photochemistry efficiency and photosynthetic gas exchange parameters under natural sunlight. The contents of photosynthetic pigments and UV-B-absorbing compounds were analyzed in terms of both leaf area and leaf fresh weight units.
Important findings Net photosynthetic rate, significantly increased after removal of UV-B components from natural sunlight. Although there was no significant difference, the F_(v)/F_(m) was increased in low UV-B treatment compared with the ambient UV-B control. Both the coefficient of photochemical quenching and actual photo- chemical efficiency of PSII in the light were higher in low UV-B treatment compared to ambient UV-B during the 16 days of continuous measurement during clear days. Variation of PSII maximum efficiency in the light and nonphotochemical quenching further confirmed that the decrease in PSII photochemistry efficiency and increase in nonphotochemical quenching were the results of a strong solar UV-B component in natural sunlight. There was only a slight increase in photosynthetic pigments based both on leaf area and fresh weight after removing UV-B radiation, and these phenomena indicated that strong solar UV-B radiation could photo-oxidize photosynthetic pigments and further accelerate the maturity and senescence of plant cells. UV-B-absorbing compounds were not altered after removal of UV-B radiation, which suggested that high levels of UV-B-absorbing compounds in the epidermal cell layer could protect photosynthetic function from UV-B.

Key words: alpine plant, chlorophyll fluorescence, photochemical efficiency, Qinghai-Tibet Plateau, UV-B radiation

师生波, 尚艳霞, 朱鹏锦, 张德罡. 滤除自然光中UV-B辐射成分对高山植物美丽风毛菊光合生理的影响. 植物生态学报, 2011, 35(2): 176-186. DOI: 10.3724/SP.J.1258.2011.00176

SHI Sheng-Bo, SHANG Yan-Xia, ZHU Peng-Jin, ZHANG De-Gang. Effects of UV-B exclusion on photosynthetic physiology in alpine plant Saussurea superba. Chinese Journal of Plant Ecology, 2011, 35(2): 176-186. DOI: 10.3724/SP.J.1258.2011.00176

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https://www.plant-ecology.com/CN/Y2011/V35/I2/176

图/表 7

表1 滤除UV-B辐射试验中主要环境因子的变化(2009年7月18日)(平均值±标准误差, n = 15; p = 0.05)

Table 1 Changes of main environmental factors in UV-B-exclusion experiments in July 18, 2009 (mean ± SE, n = 15; p = 0.05)

	amb UV-B	low UV-B	差异显著性 Significance
光合有效辐射 PAR (μmol photon·m^-2·s^-1)	1 767 ± 33	1 726 ± 43	0.398
大气相对湿度 Air relative humidity (%)	65.06 ± 0.23	64.88 ± 0.16	0.524
空气温度 Air temperature (℃)	24.09 ± 0.06	24.03 ± 0.02	0.340
紫外线-B UV-B (W·m^-2)	4.05 ± 0.10	1.74 ± 0.27	0
紫外线-A UV-A (mW·m^-2)	18.74 ± 0.28	15.27 ± 0.25	0

图1 2009年7月滤除自然光中UV-B辐射成分处理对美丽风毛菊叶片光合作用的影响。垂直条表示标准误差。*, p < 0.05; **, p < 0.01。

Fig. 1 Effects of removal of UV-B component from natural sunlight on photosynthesis in Saussurea superba in July 2009. Vertical bar is SE. *, p < 0.05; **, p < 0.01. Ci, intercellular CO2 concentration; Pn, net photosynthetic rate; Gs, stomatal conductance.

图2 2008年8月滤除自然光中UV-B辐射成分处理对美丽风毛菊叶片暗适应3 min后PSII光化学量子效率(F(v)/F(m))的影响。图中连续16天的测定中, 由于天气等原因每次的样本数目从4到22不等。垂直条表示标准误差。**, p < 0.01。

Fig. 2 Effects of removal of UV-B components from natural sunlight on 3 min dark adapted quantum efficiency of PSII photochemistry (F(v)/F(m)) in Saussurea superba in August 2008. Data numbers were from 4 to 22 during the 16 days of continue measurement due to the influence of weather condition. Vertical bar is SE. **, p < 0.01.

图3 2008年8月滤除自然光中UV-B辐射成分处理对美丽风毛菊叶片稳态PSII光化学效率的影响。垂直条表示标准误差。*, p < 0.05。

Fig. 3 Effects of removal of UV-B components from natural sunlight on light adapted photochemistry efficiency of PSII in Saussurea superba in August 2008. Fv′/Fm′, photochemical efficiency of PSII in the light; ΦPSII, actual photochemical efficiency of PSII. Vertical bar is SE. *, p < 0.05.

图4 2008年8月滤除自然光中UV-B辐射成分处理对美丽风毛菊叶片光化学和非光化学猝灭系数的影响。垂直条表示标准误差。*, p < 0.05。

Fig. 4 Effects of removal of UV-B components from natural sunlight on photochemical and non-photochemical quenching coefficient in Saussurea superba in August 2008. NPQ, nonphotochemical quenching; qp, the coefficient of photochemical quenching. Vertical bar is SE. *, p < 0.05.

表2 2008年8月滤除自然光中UV-B成分处理对美丽风毛菊叶片光合色素的影响(平均值±标准误差, n = 15; p = 0.05)

Table 2 Effects of removal of UV-B component from natural sunlight on photosynthetic pigment contents in Saussurea superba in August 2008 (mean ± SE, n = 5; p = 0.05)

		amb UV-B	low UV-B	差异显著性 Significant
叶绿素a Chl a	mg·g^-1 (FW)	1.068 1 ± 0.029 1	1.117 9 ± 0.094 8	0.645
	μg·cm^-2 (leaf area)	0.034 4 ± 0.000 8	0.038 8 ± 0.003 6	0.304
叶绿素b Chl b	mg·g^-1 (FW)	0.324 7 ± 0.011 6	0.337 3 ± 0.024 1	0.655
	μg·cm^-2 (leaf area)	0.010 5 ± 0.000 4	0.011 7 ± 0.000 9	0.276
总叶绿素 Chl a+b	mg·g^-1 (FW)	1.392 9 ± 0.040 1	1.455 2 ± 0.118 7	0.637
	μg·cm^-2 (leaf area)	0.044 8 ± 0.001 2	0.050 5 ± 0.004 5	0.297
类胡萝卜素 Car	mg·g^-1 (FW)	0.312 4 ± 0.011 9	0.335 3 ± 0.039 5	0.599
	μg·cm^-2 (leaf area)	0.010 1 ± 0.000 5	0.011 7 ± 0.001 5	0.363
Car/Chl a+b		0.224 5 ± 0.008 3	0.228 4 ± 0.010 1	0.784
Chl a/b		3.292 3 ± 0.046 5	3.305 1 ± 0.052 8	0.861

图5 2008年8月滤除自然光中UV-B辐射成分处理对美丽风毛菊叶片中紫外线吸收物质的影响。

Fig. 5 Effects of removal of UV-B components from natural sunlight on UV-B-absorbing compounds in Saussurea superba in August 2008.

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