NaCl胁迫下2种白刺光合特性适应性研究

为了解白刺光合特性适应盐胁迫的生理机制,以唐古特和西伯利亚白刺为材料,采用盆栽试验,以不施盐为对照(CK),比较8‰Na Cl胁迫40 d后,2种白刺光合色素、光合参数、叶片核酮糖-1,5-二磷酸羧化酶(Rubisco)和磷酸烯醇式丙酮酸羧化酶(PEPC)活性以及稳定碳同位素组成(δ13C值)的变化。结果表明,与CK相比,高盐处理后,唐古特白刺叶片叶绿素a(Chl a)、总叶绿素(Chl a+b)及类胡萝卜素(Car)含量分别下降了5.6%、2.1%和11.3%,叶绿素b(Chl b)增加了8.9%;西伯利亚白刺叶片Chl a、Chl b及Chl a+b含量分别下降了14.2%、15.4%和14.5%,Car含量下降了10.7%,但2种白刺光合色素的变化与CK的差异均不显著(P0.05);在有效光辐射达到1 000μmol·m-2·s-1左右时,唐古特白刺盐胁迫下净光合速率(Pn)较CK低15.4%,西伯利亚白刺较CK高10.0%,但差异不显著(P0.05)。盐胁迫下,与CK相比,唐古特白刺叶片Rubisco和PEPC活性分别下降9.9%和8.3%,胞间CO2浓度(Ci)与气孔导度(Gs)分别下降0.9%和26.4%,气孔限制值(Ls)升高,表明其Pn的下降是气孔限制与非气孔限制共同作用的结果;西伯利亚白刺叶片PEPC活性显著下降56.2%,Rubisco活性升高41.4%,Ci与Gs分别上升5.8%和35.1%,Ls降低。盐胁迫使唐古特和西伯利亚白刺叶片δ13C均值发生偏正变化,增幅分别为1.9%和1.4%,主要是盐分对其生理活动的影响所致。盐胁迫还导致唐古特白刺光补偿点(LCP)和暗呼吸速率(Rd)分别下降了30.5%和38.6%,CO2补偿点(CCP)升高了61.6%,与CK的差异达到显著或极显著水平;西伯利亚白刺LCP和Rd分别下降了15.9%和27.1%,CCP升高了26.8%,且与CK的差异达到显著水平。综上,盐胁迫造成白刺体内代谢活动减弱,但未导致2种白刺Pn的显著降低,说明其耐盐能力较强,且西伯利亚白刺盐胁迫下维持较高的Rubisco羧化效率是其耐盐能力高于唐古特白刺的内在原因之一。本研究结果为白刺在改良治理盐碱地中的应用提供了生理生态学依据。

Study on Photosynthetic Characteristics of Nitraria Under NaCl Stress

In order to understand the photosynthetic characteristics of N.tangutorum Bobr.and N.sibirica Pall.adapting to salt stress,pot experiments were carried out under NaCl mass concentration of 8‰ for 40 days with the the control of no salt stress.The key parameters such as photosynthetic pigments,photosynthetic parameters,the activivity of Rubisco and PEPC,and the changes of δ13 C of the leaves were measured.The results showed that the contents of photosynthetic pigments trended to decrease in two species under high salt stress.The Chl a,total chlorophyll content and Car content in the leaves of N.tangutorum Bobr.leaves decreased by 5.6％ 、2.1％ and 11.3％,Chl b increased by 8.9％.And the contents of Cha,Chlb,total chlorophyll and Car of N.sibirica Pall.declined by 14.2％ 、15.4％,14.5％ and 10.7％,respectively.But all the photosynthetic pigments decreasment were not significant (P ＞ 0.05) from the control.The Pn of N.tangutorum Bobr.was 15.4％ lower and N.sibirica Pall.was 10.0％ higher than that -1of the control when the effective light radiation reached about 1000 μmol · m-2· s But they were not significantly different (P ＞0.05) from the control.The activities of Rubisco,PEPC,Ci and Gs decreased by 9.9％,8.3％,0.9％ and 26.4％ in the leaves of N.tangutorum Bobr leaves,respectively,while Ls was increased.These results indicated that the decrease of net photosynthetic rate was under the influences of stomatal and non-stomatal limitation in N.tangutorum Bobr..The PEPC activity of N.sibirica Pall.leaves decreased significantly by 56.2％.Rubisco activity,Ci and Gs increased by 41.4％,5.8％ and 35.1％,respectively,and Ls decreased.The δ13C value increased by 1.9％ and 1.4％ for N.tangutorum Bobr and N.sibirica Pall.,which was mainly due to the effects of salt on its physiological activities.Salt stress also led to the decrease of LCP and Rd by 30.5％,38.6％ for N.tangutorum Bobr and 15.9％,27.1％ for N.sibirica Pall..Meanwhile,significant increase of CCP were 61.6％ and 26.8％ in the N.tangutorum Bobr.and N.sibirica Pall.,respectively.The results suggested that salt stress reduced the metobolic activity of two species of Nitraria,but was not significantly decreased the Pn,indicating that these two species of Nitraria have high salt tolerance.The higher carboxylation efficiency of Rubiso was the reason why the NaCl salt tolerate ability of N.sibirica Pall.was stronger than that of N.tangutorum Bobr..This study will provide physiological and ecological basis for using Nitraria to improve the saline land.