【作者】 王小雪；

【导师】 刘芸； 陈益泰；

【作者基本信息】 西南大学 ， 森林培育， 2012， 硕士

【摘要】 海滨木槿(Hibiscus hamabo Sieb. et Zucc.)系锦葵科(Malvaceae)木槿属(Hibiscus),落叶乔木,因极耐盐碱、水淹,抗海风,是护堤林和海岸基干林带造林先锋树种。目前对海滨木槿的育苗技术、水淹胁迫、盐胁迫等方面开展了初步研究并取得了一定成果。重金属Cd胁迫对海滨木槿家系的影响,至今罕见报道。本文以海滨木槿6家系幼苗(4月生)为材料,运用水培法研究海滨木槿对Cd(0、10、20、30 mg/L)耐性的生理生化机制及其家系间耐Cd性差异,旨在为利用木本植物修复与改善重金属污染土壤(特别是滩地)提供有益参考价值；并通过海滨木槿家系间的耐Cd性差异比较,指出重要评价指标选育优良家系,为构建东南沿海潮滩护岸林提供植物材料。结果表明：(1)Cd胁迫下海滨木槿家系幼苗生长和生理特性变化规律水培条件下,长时间(60d)的10-30mg/LCd2+胁迫,显著降低了海滨木槿家系幼苗株高净生长量和总生物量,浓度越高抑制作用越明显,胁迫初期幼苗株高净生长量增长最快,胁迫时间越长,增长幅度越小。Cd2+胁迫下海滨木槿SPAD、叶绿素荧光主要参数Fv/Fm、φps//、qP,随胁迫时间的延长而逐渐下降,NPQ逐渐上升,降低了PSⅡ活性,叶绿素分子减少是Fm降低的主要原因；同时,Cd2+胁迫改变了海滨木槿光合色素构成,Chla的合成对Cd2+更敏感,Car含量的降低表明Cd2+降低了海滨木槿非酶促抗氧化能力。随Cd2+胁迫时间的延长,海滨木槿家系幼苗叶片SOD、POD、CAT活性、SP含量均呈先升高后下降的变化趋势,它们的增加在一定程度上减轻了Cd2+的毒害作用,但它们的降低表明海滨木槿膜系统和渗透调节物质的保护作用有一定限度；SOD、CAT活性变化时间一致,POD活性被激活程度和持续时间相对长于SOD、CAT活性；SP含量到达峰值的时间较SOD、POD、CAT活性最短,表明海滨木槿幼苗SP对Cd2+更敏感,因持续时间较短易受Cd2+抑制。随Cd2+浓度增加和胁迫时间延长,海滨木槿幼苗叶片MDA含量逐步增加,细胞膜脂过氧化作用加剧。(2)海滨木槿家系幼苗根系对Cd胁迫的形态构型及生理响应长时间的10-30 mg/L Cd2+胁迫显著降低海滨木槿家系幼苗根系总长度、表面积、体积、根尖数和根系组成,且根系横向生长(根尖数和细根组成)受Cd2+胁迫影响大于根系纵向生长(根总长、根表面积、根体积),致使根系形态构型趋向简单化,浓度越高,根系空间结构越简单。Cd2+胁迫下根系MDA含量与形态参数呈显著性负相关(R=0.865,P<0.05),推测Cd2+引起海滨木槿幼苗根MDA含量升高是其根系形态构型发生改变(趋于简单化)的重要原因。随着Cd2+浓度的增加,海滨木槿幼苗根系SOD/POD、SOD/CAT均随之增大,且SOD/POD增加幅度更明显,表明海滨木槿幼苗根细胞已造成氧化损伤。海滨木槿不同家系根系耐Cd性存在差异,以家系SH3、S8表现最好,家系C25、S1表现最差。(3)海滨木槿家系幼苗对Cd胁迫的积累和耐受性10-30 mg/LCd2+胁迫60 d,不仅显著降低海滨木槿家系幼苗地上、地下生物量生产,而且明显增大幼苗根冠比,改变了其生物量分配格局。10、20、30mg/L Cd2+胁迫下,海滨木槿家系幼苗根Cd含量分别达1720、3410、4780 mg/kg,具有超高的Cd积累能力,且表现出根部富集特征。随Cd2+浓度增加,家系幼苗Cd积累量升高但生物量却降低,表明海滨木槿高生物量生产和高Cd积累能力两者不可能同时出现,Cd高积累能力会降低其潜在生物量。耐性指数显示,海滨木槿幼苗在水培Cd2+含量为10 mg/L时仍具有高Cd忍耐性(7i=69.30),对20、30mg/LCd2+胁迫具有中等程度忍耐性(Ti分别为55.53、35.21)。Cd2+胁迫引起海滨木槿不同家系Cd积累和耐性差异较大,表现良好家系为SH3、S8,最差家系为C25。(4)海滨木槿家系幼苗耐Cd性综合评价相关分析表明,Cd污染越严重,海滨木槿家系幼苗株高、生物量、SPAD、荧光参数Fv/Fm、φpS//、gP表现越差；Cd污染可明显提高海滨木槿植株POD活性以保护膜系统,同时也显著增大了非光化学猝灭系数NPQ和植物细胞体内MDA有害物质含量。主成分分析显示,Cd污染引起海滨木槿幼苗生长性状和叶绿素荧光参数的变化最明显,对土壤污染程度具有一定指示作用；POD酶活性可作为海滨木槿反映Cd污染胁迫的灵敏生理指标。此外,根系形态参数也是评价海滨木槿家系耐Cd性的有效指标。模糊数学隶属函数法综合评价海滨木槿6家系耐Cd性表明,同一海滨木槿家系针对不同指标,其抗Cd胁迫能力排序不尽一致。综合分析认为,海滨木槿6家系的抗Cd胁迫能力由强到弱依次为：SH3＞C17＞S8＞SH2＞S1＞C25。选育和利用高耐Cd性海滨木槿优良家系不仅有利于潮滩土壤Cd污染治理,而且为东南沿海防护林建设提供了植物材料。更多还原

【Abstract】 Hibiscus hamabo Sieb. et Zucc.is the deciduous arbor, which belongs to Hibiscus, Malvaceae. It is a pioneer tree species and it is always used as bank protection forest and the coastal backbone forest strip because of its saline tolerance, water-out tolerance, protection of sea wind. Some researches had been made and a certain achievements had been got on seedling-raising technique, waterlogging and salt trees of Hibiscus hamabo. There are rear researches on effects of Cd on Hibiscus hamabo families. This paper took 6 families seedlings of Hibiscus hamabo as the materials, used solution culture method to study the physiological and biochemical mechanism for Cd (0,10,20,30 mg/L) and the difference tolerance for Cd among different families. The purpose of this study was to provide useful reference for using woody plants to repair and improve soil (especially beach) polluted by heavy metal Establish comprehensive index system of superior family breeding and provide plant material for building bank protection forest on the southeast coastal through the comparison of different tolerances for Cd among different Hibiscus hamabo families. The results were as follows:(1) Growth and change of physiology of seedlings in Hibiscus hamabo families under Cd stressLong time (60 d) Cd stress decreased the net height and total biomass of seedlings in Hibiscus hamabo families significantly under solution culture. This phenomenon was observed more obviously when the concentration was high. At the early stage of sreess, net height of seedlings incrased fast, the stress time longer, the increasing range became smaller.SPAD, Fv/Fm,φps(?), qP decreased as time of stress went on of seedlings in Hibiscus hamabo families. NPQ gradually increased which decreased the activity of PSⅡ. The decrease of chlorophyll molecule was the main reason of Fm decreasing. At the same time, stress of Cd2+ changed the composition of photosynthetic pigment, the synthesis of Chla was more sensitive to Cd2+ Decreasing content of Car indicated that Cd2+ reduced the ability of antioxidation of non-enzyme systems of Hibiscus hamabo.The activity of SOD, POD and CAT, content of SP in young leaves of seedlings in Hibiscus hamabo family increased first and then decreased under Cd4 stress. The increase reduced the toxicity of Cd2+ in some degree, however, their decrease indicated that there was some limit on protection of membrane system and osmoregulation substances. Change of SOD activity was consistent with CAT activity. Degree of activated of POD and duration of POD activity was longer than SOD and CAT. Time for SP content reached to the peak was shorter than SOD, POD and CAT which indicated that soluble protein in Hibiscus hamabo was more sensitive to Cd2+. Because the duration time was short, the soluble protein was inhibited easily. Content of MDA in seedling leaves increased gradually and the preoxidation activity of membrane lipids aggravated while the concentration of Cd2+ increased and stress time prolonged. (2) Root morphological and physiological pesponses of seedlings in Hibiscus hamabo families to Cd stressLong time Cd2+ stress (10-30 mg/L) decreased the length, surface area, volume, tips and the composition of root in seedlings of Hibiscus hamabo families significantly. Effect of Cd2+ on cross-growth of root (tips and composition of root) was more obvious than longitudinal growth of root (length, surface area and volume of root) which resulted that morphologic structure of root tended to simplification. The root system spatial structure was simpler when the Cd2+ concentration was higher. There was a significant negative correlation between MDA content and morphological parameters (R=0.865, p＜0.05) under Cd2+ stress which could be conjectured that increase content of MDA in seedlings root resulted in the change of root morphologic structure (tend to simplification).Ratio of SOD/POD and SOD/CAT in seedlings root increased while concentra-tion of Cd2+ increased, the increasing range of SOD/POD was more obvious which indicated that the root cell of seedlings had been damaged by oxidation. There was differences among different Hibiscus hamabo families on endurance to Cd. SH3 and S8 had strong durance while C25 and S1 had weak durance. (3) Accumulation of Cd in seedlings and tolerance of seedlings in Hibiscus hamabofamilies under Cd stressStress of Cd+(10-30 mg/L) for 60 d decreased biomass of seedling both above and under ground, increased the ratio of root-shoot, changed the distribution pattern of biomass. Under 10,20,30 mg/L Cd2+ stress, Cd content of root in seelding was 1720. 3410,4780 mg/kg respectively, which showed that Hibiscus hamabo had super ability to accumulate Cd and the enrichment of Cd was observed in root. The amount of Cd accumulation increased while biomass decreased when concentration of Cd increased, which indicated that high biomass of plant and super ability of accumulating Cd could not appear at the same time. High ability of accumulation decreased potential biomass of plant. Cd tolerance index showed that Hibiscus hamabo seedlings had high Cd tolerance (Ti=69.30) when concentration of Cd2+ was 10 mg/L. Tolerance of Cd under 20 and 30 mg/L was medium and the tolerance index was 55.53,35.21 respectively. There were significant difference on Cd accumulation and Cd endurance among different Hibiscus hamabo families under Cd stress.The best two families were SH3 and S8 while the worst family was C25. (4) Comprehensive evaluation on Cd tolerance among Hibiscus hamabo familiesThe height, biomass, SPAD, Fv/Fm,φPSⅡand qP of Hibiscus hamabo decreased when Cd pollution was serious. Cd pollution could increase the activity of POD in order to protect the membrane system of Hibiscus hamabo plant. At the same time, Cd pollution increased NPQ and content of MDA in plant cells significantly.Analysis of principal component showed that the change of growth characters and chlorophyll fluorescence parameters of Hibiscus hamabo seedlings was most obvious under Cd stress. These change had indicative function to contamination degree of soil. The activity of POD could reflect the tolerance of Hibiscus hamabo under Cd stress. Root morphological parameters could also be used to reflect the Cd tolerance of Hibiscus hamabo families.Comprehensive appraisal of characters on Cd tolerance among 6 Hibiscus hamabo families showed that tolerance order to Cd were different when different itms were studied in one family. It was concluded t at the tolerance order was SH3＞C17＞S8＞SH2＞S1＞C25 among 6 Hibiscus hamabo families. Breeding and using Hibiscus hamabo families which had strong tolerance to Cd was benifical to control the pollution of Cd in tidal flats soil and proided valuable plant materal to construction of protection forest in southeast coast.更多还原