高山植物唐古特山莨菪和唐古特大黄对强太阳辐射光能的利用和耗散特性

 以西宁地区人工栽培的唐古特山莨菪（Anisodus tanguticus）和唐古特大黄（Rheum tanguticum）为材料,比较研究了两典型高山植物对青藏 高原强太阳辐射光能的利用和耗散特性。PSⅡ反应中心的最大光化学效率(F_v/F_m)、实际光化学量子效率(ΦPSⅡ)和光合功能的相对限制(L (PDF))的分析表明,强太阳辐射会导致光合作用的光抑制,但并不造成PSⅡ反应中心的不可逆破坏。猝灭分析表明,唐古特山莨菪的光化学猝 灭系数(q_P)显著小于唐古特大黄,非光化学猝灭(NPQ)和(q_N)则相反（p<0.05）,意味着唐古特山莨菪将PSⅡ反应中心吸收的过剩光能以热耗散 等非光化学过程消耗的能力大于唐古特大黄,因而降低了用于光化学反应的份额。q_N的3组分中,q_Nf所占比例较大;尽管相对份额很小,中午 强光下两高山植物的qNm都有增大趋势,表明它在过剩光能的非光化学耗散中也起重要作用。NPQ_S和q_Ns的日变化趋势很相似;同样,NPQF为NPQ 的主要组分,且唐古特山莨菪的NPQ_F和q_Nf都显著大于唐古特大黄（p<0.05）。唐古特山莨菪PSⅡ天线色素吸收光能中分配于光化学 反应的 相对份额(P)始终低于唐古特大黄,而用于天线热能耗散的相对份额(D)则大于唐古特大黄,两者都具有极显著差异（p<0.01）。以上结果表明 ,唐古特山莨菪的ΦPSⅡ较唐古特大黄小是因为PSⅡ天线色素吸收的光能中分配于光化学反应的相对份额或光化学猝灭的比例较小,而分配于 天线热耗散的相对份额或非光化学过程的比例较大的缘故。唐古特山莨菪的NPQ和q_N较大,与NPQ_F和q_Nf以及NPQ_S和q_Ns都显著大于唐古特大黄有 关（p<0.05）。

UTILIZATION AND DISSIPATION OF STRONG SOLAR RADIATION IN TWO ALPINE PLANTS, ANISODUS TANGUTICUS AND RHEUM TANGUTICUM

Aims The Qinghai-Tibet Plateau is characterized by high elevation, thin atmosphere and high solar transparency. Strong solar radiation is a major stress factors during the growing season. Means of defense and dissipation of strong solar radiation rarely have been explored. Our objective is to determine solar utilization and dissipation characters in two native alpine plants, Anisodus tanguticusand Rheum tanguticum. Methods We used data obtained from a portable pulse amplitude modulation fluorometer (FMS_2, Hansatech Co., UK) to explain the characteristics of utilization and dissipation and components of non-photochemical quenching. Important findings Strong solar radiation could cause the photoinhibition of photosynt hesis, but this constitutes reversible destruction to PSⅡ reaction center in both alpine plants. Quenching analysis of chlorophyll fluorescence indicated that A. tanguticus could dissipate more excess excitation energy in PSⅡ antennae through non-photochemistry progress than R. tanguticum, as the fraction of energy utilized in photochemistry was decreasing. Dark relaxation kinetics analysis showed that “fast" component q_Nf was the main fraction of q_N, then “slow" component q_Ns. “Middle" component q_Nm was lower than q_Ns, but it had an increasing tendency accompanied increased light at noon, which indicated that q_Nm still played an important role in non-photochemical quenching. Diurnal variations of NPQ_S and q_Ns were similar in the two plants; the same as q_Nf, rapidly relaxing quenching NPQ_F was also the main component in non-photochemical quenching NPQ, and both NPQ_F and q_Nf were significantly higher in A. tanguticusthan in R. tanguticum(p<0.05). The fraction of light energy absorbed in PS Ⅱ antennae, which is utilized in PSⅡ photochemistry (P), was significantly lower in A. tanguticus than inR. tanguticum (p<0.01), but the fraction that was dissipated thermally (D) was significantly higher in A. tanguticus than inR. tanguticum (p<0.01). The midday depression of the excess excitation that was neither utilized in photosynthetic electron transport nor dissipated thermally (Excess) showed that there was a light stress acclimation in the two alpine plants. The study indicates relatively lower proportion of P and q_P in A. tanguticus than in R. tanguticum and the higher fraction ofD and NPQ and q_N, so actual photochemistry efficiency ΦPSⅡ was lower in A. tanguticus than in R. tanguticum. Higher level of NPQ and q_N mainly results from the NPQ_F and q_Nf, as well as NPQ_S and q_Nsin A. tanguticus compared to R. tanguticum.