摘要
为了探讨白刺花(Sophora davidii(Franch.)Skeels)幼苗对持续干旱胁迫的适应能力及对策,用盆栽方法人工模拟土壤干旱条件,设置土壤田间持水量(WHC)100%、80%、60%、40%和20%5个干旱胁迫处理,研究了幼苗生长、生物量分配、水分利用效率(WUE)、叶形态解剖结构以及光合色素等在不同干旱胁迫强度下的变化特点。结果显示,胁迫处理96d后,100%WHC条件下白刺花幼苗的总叶面积、分枝数、基径及最大根长等均最大;80%WHC对幼苗产生了轻度胁迫,随着干旱胁迫强度的进一步增加,幼苗生长显著减小。干旱胁迫限制了新生叶发生与单叶面积扩展,导致冠层总叶面积减小,从而引起幼苗光合能力及生物量积累均降低。随着胁迫强度的增加,叶生物量所占的比例及叶面积/根生物量的比值都明显减小,而根生物量所占的比例增大,这说明叶生长对干旱胁迫反应比根更加敏感。另外,干旱胁迫下WUE随着生物量与耗水量的减小而降低,表明幼苗具有浪费型水分利用对策。叶绿素(Chla、Chlb和Chla+b)及类胡萝卜素含量(Car)都随着干旱胁迫增强而呈增大趋势,但Chla/b及Chl/Ca变化趋势相反。干旱胁迫对叶片解剖结构影响较小,土壤水分减少时仅栅栏组织厚度略有增厚,海绵组织变薄。研究结果证明,60%WHC是幼苗生长、生物量积累、WUE和光捕获复合体活性受到明显抑制的干旱胁迫强度阈值;20%WHC胁迫处理对幼苗产生了严重危害。但是在实验过程中,即使在20%WHC条件下也未出现叶片凋落及幼苗死亡,表明当年生白刺花具有较强的干旱忍受能力,幼苗通过减小地上蒸发面积、增加地下生长及叶绿素含量等多种形态与生理策略适应干旱胁迫。
Sophora davidii,an endemic leguminous shrub,is a potential tool species for vegetation and ecosystem rehabilitation in the arid region of the upper reaches of the Minjiang River,southwest China.In order to assess the ability of tolerating drought in the species,we investigated the effects of drought stress on growth,biomass production and partitioning,water-use efficiency,leaf anatomical characteristics and photosynthetic pigment contents of S.davidii seedlings.Two-month-old seedlings were grown under water supply regimes of 100,80,60,40 and 20% water-holding capacity(WHC),respectively,in an open-sided greenhouse.Leaf area,branch number,basal diameter,root length,root mass per soil volume,biomass production and WUE were the greatest in the seedlings of 100% WHC treatment,and they slightly declined in 80% WHC but were greatly reduced in 60%-40% WHC and were severely retarded by 20% WHC.As expected,drought induced an increase in root mass fraction and a decrease in leaf mass fraction,thereby maintaining a balance between water-losing and water-obtaining processes.Drought stress increased palisade mesophyll thickness while reduced spongy mesophyll thickness.Moreover,drought significantly increased Chla,Chlb,Chla+b,and carotenoid contents(Car),but decreased the ratios of Cha/b and Chl/Car.The results demonstrated that S.davidii seedlings avoid or tolerate drought by reducing branching intensity and leaf area while maintaining a high percentage of root mass and chlorophyll content in leaves.The fact that there was no mortality and leaf shedding in the seedlings even under 20% WHC condition indicates that this native N-fixing shrub species has a great potential for vegetation restoration in dry valleys of the Hengduan Mountain and other arid regions.
出处
《生态学报》
CAS
CSCD
北大核心
2009年第10期5406-5416,共11页
Acta Ecologica Sinica
基金
中国科学院知识创新工程资助项目(KZCX2-XB2-02)
中国科学院"西部之光"博士资助项目(08C2041100)
关键词
干旱胁迫
白刺花
叶形态结构
叶绿素
生物量分配
水分利用对策
drought stress
Sophora davidii
morph-anatomical traits
chlorophyll
biomass partitioning
water-use strategy