【作者】 李德明；

【导师】 朱祝军；

【作者基本信息】 浙江大学 ， 蔬菜学， 2003， 博士

【摘要】 不结球白菜是人们喜食的绿叶蔬菜之一，由于长期自然和人工选择，现存在丰富的品种类群。随农田污染日益严重，不结球白菜生产易受镉（Cd）污染危害。因此，筛选低Cd积累不结球白菜品种，能为生产安全蔬菜提供重要保证。同时，已有证实植物对Cd的吸收、积累与生长环境有关，因此通过改进农艺条件也可降低不结球白菜对Cd的吸收、积累。目前有关植物对Cd的吸收、积累的基因型差异机理尚存在争议，因此有必要进行相关研究。本论文从不结球白菜基因型差异筛选入手，利用水培试验，较为系统地研究了Cd影响不结球白菜生长及其Cd积累基因型差异的生理机制，并探索了某些外源物质如硅（Si）、硒（Se）对减少不结球白菜Cd吸收、积累的影响机理。 1、不结球白菜Cd积累不同基因型差异 于春夏和秋冬两生长季节在Cd污染(6 mg·kg^-1 Dry soil)土壤中进行87个品种不结球白菜Cd积累差异研究。结果表明，不同品种Cd积累存在明显的基因型差异，同一品种春夏季Cd积累量高于秋冬季。品种、生长季节、季节与品种互作间差异均达极显著水平，表明小白菜安全生产应选择适宜品种、适宜栽培条件与栽培季节。 2、Cd在不同品种小白菜中亚细胞分布的研究 以差速离心法研究Cd在不同品种小白菜亚细胞的分布情况。结果表明，Cd在各器官中的含量依次为根系＞叶片＞叶柄，并且存在品种差异。在各器官的细胞中，Cd主要分布在细胞可溶性成分、细胞壁和质体（或叶绿体）中，而在细胞核、线粒体和核糖体中Cd分布量较少。根系与叶片四种重要细胞器（质体（或叶绿体）、细胞核、线粒体和核糖体）中的Cd分配率随Cd处理浓度的增加而增加，沪青一号上升更明显；叶柄中，线粒体和核糖体Cd分配率随Cd处理浓度的增加而增加，但叶绿体和细胞核Cd分配率下降，沪青一号四种细胞器Cd分配率高于苏州青。各细胞器中Cd分配率受Cd处理浓度影响，沪青一号各器官的细胞生命活动均较苏州青受Cd危害严重。 3、Cd对小白菜光合特性的影响 微量Cd(0.01mg·L^-1)促进小白菜生长，对苏州青作用更明显；高浓度Cd显著抑制地上部生长，对根系生长影响相对较小。Cd降低叶绿素含量，苏州青降幅较大。高浓度Cd(1、10 mg·L^-1)明显降低小白菜净光合速率（Pn），但增加胞间CO₂浓度（Ci），因此高浓度Cd降低Pn可能是由于非气孔限制所引起的。叶绿素荧光测定表明，Cd对小白菜叶片光化学效率（Fv／Fm）影响不大，而高浓度Cd明显降低光合电子传递量子效率（ΦPSⅡ）、光化学淬灭系数（qP）和电子传递速率（ETR）。Cd增加沪青一号非光化学淬灭系数（qNP），而苏州青在高Cd浓度下qNP下降，表明沪青一号具有较强的保护自身光合机构不受Cd伤害的能力，苏州青自身保护能力稍弱。 4、不同Cd水平对小白菜生长和Cd、养分吸收的影响 0.1～1 mg·L^-1Cd对不同品种小白菜生长影响不同，其中苏州青与湘潭束腰受抑制。0.1 mg·L^-1Cd不影响叶绿素含量，但除湘潭束腰外，1 mg·L^-1Cd减少叶绿素含量。0.1 mg·L^-1Cd减少苏州青和油冬儿的 挝，但对湘潭来腰、沪歼一号影响不人：及鹏·卜‘U明显减少湘潭范腰、苏州青、油冬儿植株的硼g量，但沪青一号U处理前洲蒸腾量反而有所增加。小白菜叶片、叶柄C(！含举及积累量随M处理量升高而增加，0－I柄Cd含量、积累量显为低于叫片。0．l。g·L－‘Cd处理时，各品种叶片Cd含量差异未达显著水平，而IDWe柄差异达显著水平，油冬儿山含量最高，苏州卉最低。1峪·卜‘M处理时，叶片比含量差异仍未达显著水平，而叶柄中差异达显著水平，油冬儿m含量最高，沪青一号剔氏。C(1处理降低小白菜地上部P、S的含量。ling·I。－‘Cd处理降低小白剩也上部K、I4g含量，但叶柄Ca含量相对降低而叶片相对升高；0．ling·L’Cd处理促进地上部贴积累。小白拟L上部微挝元素含蒸受Cd影响逐渐降低。5、不同浓度＆对小白菜活性气清除系统的影响 低剂挝Cd（＄1 mg·L－’）处理促进小白菜GSH、AsA和脯氨 量升高，苏州青中二者含挝均低于沪青一号。比降低可溶蛋白质含量，沪青一号显著低于苏州青。低剂量m处理增加叶片p A含泉，但沪青一号峪低了苏州青。低n略促进沪青一号超氧囱由基产生速率，苏州青则先显斡降低随h浓度增加后显著升高。低剂挝Cd降低小肉菜 SOD活性，两品种芹异不人；两品种G－pD、CAT。APX和 DIWi活性均受低剂钨n促进；低剂烘U促进苏州青朋活性，但抑制沪青一号m活性。6、Cd对菜心生长和元素含量基囚型差异研究 0．5。g·L－’Cd明显抑制全年i巾青生K，但对其它品种影响不人；1。g·L创显达抑制各品种地上部生K，且对全年汕青、洲8四九和测a菜起地卜部生K抑制效贝显茗。比(＜1峪·丫〕略降低菜心地上部含水挝，lllg·L－’Cd显著增加红苔菜与十月细恰冠比。Cd（＜1 gig·L‘）显著增加各品种地上部、地下部m含堆，除改良黄叶外，1吧·八d处理时各品种地上部、地卜部m含填均显斡高于队加；g·L‘U处理。0．5。g·厂’U显垮增加改良询w地V部P、h含挝、十月红地上部S、吨、N、h和m含挝、别8四九和红苔剿也上部h含量以洲R问菜途地下部N和h含量，显著?更多还原

【Abstract】 Pakchoi ( Brassica campestris ssp. chinensis L. ) is a very important green leafy vegetables in China, and has abundant genotypes from long time natural and artificial selection. In the production, pakchoi is easily polluted by Cadmium (Cd), which is one of the most toxic heavy metals to both plants and animals. It is one of best cost-effective and efficient approaches to choose cultivars of pakchoi with low Cd accumulation in edible parts. Meanwhile, it has been demonstrated that growth environmental factors may influence Cd absorption and accumulation in plants. It would thus be beneficial to reduce Cd uptake and accumulation in pakchoi by agronomic practices. The mechanism about the plant genotypic difference in Cd absorption and accumulation still be disputed. These experiments will be carried out to study the physiological mechanism of genotypic difference in effects of Cd on growth of pakchoi, Cd-uptake and accumulation in pakchoi plants, based on the research of genotypic difference of Cd contents in shoots of pakchoi and Cd subcellular distribution in plants of pakchoi. Meanwhile, the possibility to reduce Cd uptake and accumulation in pakchoi plants by application of Silicon (Si) or Selenium (Se) will be also studied. The major results were summarized as fellows:1. Investigation of genotypic difference of Cd contents in shoots of pakchoiDifference of Cadmium (Cd) contents in shoots of 87 cultivars of pakchoi ( Brassica campestris ssp. chinensis 1.) were studied in a Cd-contaminated soil (6 mg Cd kg-1 ) in two growth seasons. The results showed that significant differences of shoot Cd contents were found among the genotypes (cultivars). Cd contents of pakchoi in spring and summer were higher than in autumn and winter. The results of ANOVA showed highly significant differences of genotype (cultivar), growth season and cultivar growth season interaction for shoot Cd contents. The results indicated the significance to choose suitable cultivars, growth conditions and growth seasons to produce safe pakchoi.2. Cd subcellular distribution in plants of pakchoiCd contents in different pakchoi plant parts were as follows: root > blade > petiole. Cd was mainly distributed in fractions of soluble component, cell wall and chloroplast (or plastid in root) and less distributed in fractions of nucleolus, mitochondrion and ribosome. In four important organelles (plastid(or chloroplast), nucleolus, mitochondrion and ribosome) of the root and blade cells, Cd distribution rates were increased with increasing of Cd treated concentrations, especially more significantly in Huqingyihao. In the petioles, Cd distribution rates were increased with Cd concentration in mitochondrion and ribosome, but decreased in chloroplasts and nucleolus. Cd distribution rates in four most important organelles (chloroplast, nucleolus, mitochondrion and ribosome) of Huqingyihao were higher than in Suzhouqing in petiole. BecauseCd increasing with the increasing of Cd concentration in the important organelles in Huqingyihao was much higher than in Suzhouqing, the damage on cellular life activities by increasing Cd concentration in Huqingyihao would be stronger than in Suzhouqing.3. Influence of Cd on photosynthesis of pakchoiLow concentrations of Cd (0. 01, 0. 1 mg L"1) promoted plant growth, especially more considerably on Suzhouqing. High concentrations of Cd (10 mg L"1) significantly inhibited the shoot growth, however, didn’ t affect the root growth. Cd decreased chlorophyll content, especially on Suzhouqing. High concentrations of Cd (1-, 10 mg L"1) considerably reduced net photosynthesis rate. The reduction on stomatal conductance and increase on intracellular Cft (Ci) under high concentrations of Cd indicated that a non-stomatal restriction resulted in an decrease of net photosynthesis. The determination of chlorophyll fluorescence showed that Cd didn’ t influence photochemical efficiency of PSH(Fv/Fm). High concentrations of Cd reduced actual quantum yield of PSIl(<t>PSII), photochemical quenching (qP) and elec更多还原