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地下水埋深对胡杨叶片光合作用及抗氧化物质积累的影响

Response of Photosynthesis and Antioxidants to Groundwater Depth in Leaves of Populus euphratica Oliv.

  • 摘要: 以塔里木荒漠生态系统建群种—胡杨(Populus euphratica Oliv.)为试材,研究胡杨光合气体交换参数、抗氧化酶活性及渗透调节物质沿地下水埋深(GWD)梯度的变化规律,探讨胡杨适应干旱荒漠环境的生理生态机制。结果表明:(1)不同GWD条件下胡杨净光合速率(P_n)、蒸腾速率(Tr)、气孔导度(Gs)的日变化均呈单峰型,而胞间CO2摩尔分数(Ci)日变化呈“V”型,P_n与Gs变化同步,峰值均出现在12:00,而Tr峰值滞后P_n、Gs2 h。不同GWD间P_n峰值差异显著(P<0.05),Tr、Gs峰值和Ci谷值在GWD为5.5 m极显著降低(P<0.01)。胡杨P_n、Tr、Gs、Ci、水分利用效率(WUE)和光能利用效率(LUE)均随GWD增加而降低,其中Gs、LUE日均值在GWD为5.5 m显著降低(P<0.05),但不同GWD条件下P_n、Tr、Ci、WUE日均值均无显著差异(P>0.05);(2)12:00—16:00胡杨P_n下降主要受气孔因素限制,16:00—20:00 P_n下降主要受非气孔因素限制;(3)通过对不同GWD条件下胡杨P_n、Tr与生理生态因子进行相关、偏相关、逐步回归分析发现,Gs是影响胡杨P_n、Tr的主要因子;不同GWD条件下胡杨调控P_n、Tr的因子不同,GWD增加使胡杨P_n与光合有效辐射(PAR)、Tr与Gs之间的相关性增强,表明GWD直接调控胡杨叶片水汽交换(Gs)过程;(4)胡杨叶片丙二醛(MDA)含量、超氧化物歧化酶(SOD)活性、过氧化物酶(POD)活性和游离脯氨酸(Pro)含量均随GWD增加而增大,而可溶性蛋白质(SP)含量、可溶性糖(SS)含量则降低,表明随GWD增加,胡杨叶片细胞膜透性和光合碳同化受抑增强,胡杨通过提高保护酶活性(POD、SOD)和渗透调节(Pro)能力协同抵御地下水位降低所带来的干旱胁迫,以维持基本正常的生理活动,这是胡杨适应荒漠区干旱生境的生理生态策略。

     

    Abstract: In order to explore the eco-physiological mechanism of Populus euphratica Oliv adapting to the arid desert environment,P.euphratica Oliv.that the key species in the Tarim desert ecosystem was used as material.It was conducted to research the change of photosynthetic gas exchange,antioxidative enzyme activity and osmoregulation substances of P.euphratica grown at different groundwater depths(GWD).The results showed that:(1)the diurnal courses of net photosynthetic rate(Pn),transpiration rate(Tr)and stomatal conductance(Gs)of P.euphratica under different GWD conditions showed the single peak curves respectively,while the diurnal variation of intercellular CO2mole fraction(Ci)were the“V”curve,the valley value was significantly reduced at GWD=5.5 m(P<0.01)respectively.Pna nd Gs changed synchronously,and the peak value appeared at 12:00,while the Tr peak value lagged 2 hours.The peak values of Pn in different GWD were significantly different(P<0.05),while the peak values of Tr,Gs and Ci valley were significantly reduced in GWD=5.5 m(P<0.01)respectively.Pn,Tr,Gs,Ci,water-use efficiency(WUE)and light utilization efficiency(LUE)decreased with GWD increasing,and the daily mean value of Gs and LUE significantly decreased at GWD=5.5 m(P<0.05)respectively.However,there was no significant difference in the daily mean values of Pn,Tr,Ci and WUE under different GWD conditions(P>0.05)respectively;(2)The decline of Pnin P.euphratica from 12:00-16:00 was mainly restricted by stomatal factors,while the decline of Pnfrom 16:00-20:00 was mainly limited by non-stomatal factors;(3)The relationship between eco-physiological factors and Pn,Trunder different GWD conditions were analyzed with correlation,partial correlation and stepwise regression methods,it was found that Gswas the main factor affecting Pnand Trof P.euphratica respectively.The correlation degree between Pnand photosynthetically active radiation(PAR),Tr and Gs were enhanced respectively with GWD increasing,indicating that GWD directly regulated the airwater exchange;(4)The malondialdehyde content(MDA),superoxide dismutase activity(SOD),peroxidase activity(POD)and free proline content(Pro)were increased respectively with GWD increasing,but the content of soluble protein(SP),soluble sugar(SS)were both decreased,which indicated that the cell membrane permeability and photosynthetic carbon assimilation were inhibited respectively with GWD increasing.P.euphratica enhanced the protective enzyme activity(POD,SOD)and osmoregulation content(Pro)to cooperate against drought stress caused by GWD increasing,and ensured to maintain the basic normal physiological activities.This was the eco-physiological strategy for P.euphratica to adapt arid desert environment.

     

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