三叶木通叶片解剖结构和光合特征对干旱胁迫的响应

Responses of Akebia trifoliate leaf anatomical structure and photosynthetic characteristic to drought stress

  • 摘要: 目的分析干旱胁迫下三叶木通叶片的解剖结构和光合特性,为西南喀斯特石漠化区生态修复植物材料选择提供参考依据.方法盆栽喀斯特地区适生植物三叶木通并进行连续干旱胁迫处理,采用常规石蜡切片法和Li-6400光合仪分别测定其幼苗叶片的解剖结构参数和光合参数,分析解剖结构和光合生理特征变化,以及二者间的相关性.结果随土壤相对水含量(SRWC)的降低,三叶木通幼苗叶片呈厚度变薄、水含量降低和栅栏组织缩短变紧密等变化趋势;总叶绿素(Chlt)含量、净光合速率(Pn)、气孔导度(Gs)和蒸腾速率(Tr)下降,水分利用效率(WUE)提高;SRWC降至29%时,大部分解剖指标和光合指标呈显著性差异变化(P<0.05).主成分分析结果表明,大于1.000的叶片解剖指标特征值中有4个主成分的载荷值差异极大,贡献率达88.195%,主要指标为栅栏组织、下表皮、木质部和海绵组织;大于1.000的叶片光合指标特征值有2个主成分的载荷值差异极大,贡献率达83.277%,指标为Gs和Chlt.相关性分析结果表明,SRWC与叶片水含量(LWC)、Chlt、Pn、Gs、胞间CO2浓度(Ci)、Tr、气孔限制值(Ls)及叶片解剖结构中的叶片厚度、栅栏组织厚度和木质部厚度均呈极显著正相关(P<0.01,下同),与WUE和叶片组织结构疏松度呈极显著负相关.结论三叶木通幼苗在干旱胁迫下通过改变叶片结构特征、降低光合作用和提高水分利用效率等方式适应干旱频发的喀斯特环境;SRWC为29%可视为三叶木通幼苗受干旱胁迫的起点;栅栏组织、海绵组织、木质部及Gs可作为三叶木通耐旱性品种筛选的参考指标.

     

    Abstract: ObjectiveThe anatomical structure and photosynthetic characteristics of leaves of Akebia trifoliate were observed and measured under drought stress to provide references for selecting suitable plants for ecological restoration in karst rocky desertification area in southwest China.MethodA. trifoliate,a karst adaptable specie,was taken as material. Through pot experiment and continuous drought stress,seeding leaf anatomical structures were observed by conventional paraffin section,and changes of photosynthetic physiological characteristics were analyzed by measuring photosynthetic parameters with Li-6400. The changes of anatomical structures and photosynthetic characters and the correlation between the two were analyzed.ResultWith soil relative water content(SRWC)decreasing,the thickness of seeding leaf thinned, water content decreased and palisade tissues shortened in the structural features of the leaves of A. trifoliate. Chlorophyll content(Chlt),photosynthetic rate(Pn),stomatal conductance(Gs),transpiration rate(Tr)decreased,water use efficiency (WUE)increased. Most of the anatomical and photosynthetic indicators showed significant difference when SRWC de-creased to 29%(P<0.05). The results of principal component analysis showed that the load values of four principal compo-nents in the characteristic values of leaf anatomy greater than 1.000 varied greatly,with a contribution rate of 88.195%. The main indicators were palisade tissue,lower epidermis,xylem,and spongy tissue. Among these photosynthetic index eigenvalues of leaves which were larger than 1.000,Gs and Chlt were two main components with large differences in load values,with a contribution rate of 83.277%. The correlation analysis showed that there was significant positive correlation between SRWC and leaf water content(LWC),Chlt,Pn,Gs,Ci,Tr,Ls,leaf thickness,palisade tissue thickness and xylem thickness in leaf anatomy(P<0.01,the same below). There was extremely significant negative correlation between WUE and leaf structure loose degree(SR).ConclusionBy changing the structure characteristics,reducing photosynthesis and increasing water use efficiency under drought stress,seedlings of A. trifoliate can adapt to the karst environment in south-west China where drought take place frequently. SRWC of 29% can be regarded as the starting point of drought stress of A. trifoliate seedlings. Palisade tissue,spongy tissue,xylem and G s can be used as reference indexes for the screening of drought-tolerant varieties of A. trifoliate.

     

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