【作者】 洪春来；

【导师】 翁焕新；

【作者基本信息】 浙江大学 ， 环境科学， 2007， 博士

【摘要】 碘的缺乏将会引起人体甲状腺肿大症,这己成为全球范围的一大公共卫生问题。为防治碘缺乏症（IDD）的发生,本文利用农业生物强化法提高蔬菜中碘的含量以改善人体碘的营养水平,从而探询更为高效、安全的补碘新途径。本研究以各种类型的蔬菜为栽培作物,选取不同形态的有机、无机碘和海藻碘肥作为外源碘,采用水培、土培、大田等多种栽培方式及常规和同位素研究法深入探讨碘在土壤-蔬菜系统中的环境生物地球化学行为及蔬菜富集碘的机制,从而为富碘蔬菜的筛选及碘的农业生物强化法的产业化应用推广提供切实的理论和技术依据。取得的主要结果如下:1.水培条件下外源碘的添加对蔬菜的生长均具有明显效应,在低浓度的碘水平下（＜0.5 mg/L）,外源碘能促进蔬菜生长,但高浓度的碘会对蔬菜的生长产生抑制作用。供试蔬菜都具有一定的吸收与积累水培液中外源碘的能力,随着外源碘浓度的提高,蔬菜可食用部位碘的含量均随之增加,蔬菜对三种不同形态外源碘的吸收能力总体表现为F＞CH₂ICOO^-＞IO₃^-;三类不同蔬菜中以叶菜类对碘的吸收能力最强,其次为茎菜类,而果菜类蔬菜对碘的吸收能力相对较弱。小白菜不同基因型对外源的吸收及生长反应存在明显的差异,其中苏州青、矮脚青等基因型对碘的吸收及耐碘毒害的能力均较强。2.水培条件下蔬菜碘吸收速率在短时间内迅速上升达到最高值后随着时间的延长逐步下降。在低浓度下（＜0.5 mg/L）蔬菜IO₃^-吸收速率与浓度之间的曲线图符合酶促反应动力学方程,具有元素主动吸收的基本特征。而在高碘浓度范围内（0.5-10.0 mg/L）,蔬菜碘吸收速率随着外源碘浓度的提高呈现直线增加,反映了被动吸收特征。在一次供碘连续培养条件下蔬菜可食部位吸收碘的量随着处理时间的延长表现出前期上升后期下降的趋势,而在连续供碘条件下蔬菜可食部位碘的含量则表现出持续增加的趋势;在低浓度下（0.1 mg/L）蔬菜对IO₃^-的吸收能力强于I^-,而在较高浓度下（5 mg/L）,蔬菜对I^-的吸收量明显高于IO₃^-。培养溶液中Cl^-的加入降低了低碘浓度下蔬菜碘吸收速率,而随着碘浓度的增加Cl^-对蔬菜碘吸收速率的影响逐渐减弱。3.两种形态的碘在3种菜园土上的吸附平衡均可采用Langmuir、Freundlich等吸附方程来拟合。土壤吸附态碘的解吸量随着碘吸附量的增加而增加。两种碘源中,IO₃^-更容易被土壤所吸附;3种土壤中,黄筋泥对碘的吸附能力最强而吸附态碘的解吸率最小,其次为青紫泥,而黄松土对碘的吸附能力最弱而吸附态碘的解吸率最高。碘在固液（土壤-平衡液）两相之间的分配系数（K_d）随着外源碘添加量的增加而迅速下降。4.加入到盆栽土壤的两种不同形态外源碘（I^-,IO₃^-）中,I^-更易被小白菜所吸收,对小白菜的毒性也更强,但在土壤中相对容易损失;3种菜园土中,黄松土中碘的生物有效性最强但碘的损失率也较高。而碘在黄筋泥中的生物有效性相对较低但碘的持效性最长。¹²⁵I在施入盆栽土壤后绝大部分就近被土壤所吸附,仅有很少一部分能迁移到土壤底层和外层;无论纵向还是横向迁移速度都是青紫泥较黄松土快。一段时间（8d）以后土壤和植物中都有部分碘被转化为挥发性碘而损失。5.土培条件下蔬菜中碘的含量均随土壤外源碘浓度的提高而增加;不同蔬菜对碘的吸收与积累能力呈现出叶菜类的大白菜最强,其次为茎菜类的莴苣,而根菜类的胡萝卜和果菜类的番茄相对较弱;供试蔬菜对碘毒害的耐性表现为胡萝卜＞大白菜＞莴苣＞番茄。在第1茬时,KI更容易被蔬菜所吸收但毒性也更大;在第2茬时,海藻碘添加的蔬菜中碘含量则更高。连续种植两茬后,施用KI的土壤中碘残留量的下降幅度明显大于施用海藻碘肥的土壤,蔬菜种植明显加速了土壤中碘的亏损。6.海藻碘肥田间施用效果表明,供试蔬菜可食部位对碘的吸收均随着海藻碘肥添加浓度的提高而增加,其中叶菜类对海藻碘的吸收与积累能力最强,其次为茎菜类和根菜类,而果菜类可食部位对海藻碘的积累能力最弱。随着取样时间的延后,蔬菜可食部位对海藻碘的吸收除了大豆外均总体呈现出下降的趋势。两种不同的海藻碘肥施用方式中,土施更有利于蔬菜对碘的吸收和积累。在土施条件下,碘在根菜不同部位的分配表现为地上部分高于块根,而碘在其它蔬菜不同部位的分配表现为根＞叶＞茎＞果实;在海藻液体碘肥喷施条件下蔬菜各部分中则是叶子的碘含量最高,其次为茎,而果实和根中碘积累量较低;两种栽培方式下,设施栽培较露天栽培更有利于蔬菜各部位对碘的吸收和积累。7.¹²⁵I添加下蔬菜体内碘的存在形态的分析表明,小白菜中水溶性碘主要以I^-形式存在,占总水溶性碘的66.7%,而有机结合碘则主要以蛋白质结合碘为主,占总碘的22.4%。小白菜所吸收的碘主要分配于细胞可溶部分,占了细胞总碘的54.8%-63.9%,其次为细胞器和细胞壁部分。随着外源碘浓度的提高,碘在细胞壁的分配比率有增加的趋势。碘在小白菜根细胞内主要定位于细胞壁附近的纤维组织中,而在小白菜茎、叶细胞内则主要存在于叶绿体中。更多还原

【Abstract】 It has been well known that iodine deficiency can result in goiter,and this has become a global sanitation problem.In order to reduce the incidence of iodine deficiency disorders（IDD）,the agricultural biofortification was used to increase iodine content in vegetable of human food chain to improve human nutrition.In our studies,the vegetable was cultivated as target crops and different forms of iodine （inorganic and organic） including seaweed were chosen in hydroponic,pot and field experiment,which were carried out to investigate the biogeochemical characteristics of iodine and mechanism of iodine enriched by vegetable.The objectives of the studies are to provide theoretic basic for the breeding of iodine-enriched vegetable and popularizing of iodine biofortification in practice,and ultimately to seek an effective,safe and scientific approach to the prevention and cure of iodine deficiency disorders（IDD）.The main conclusions obtained from our studies are as follows:1.In the hydroponic experiment,the low levels of iodine（＜0.5 mg/L） can promote the biomass of vegetable efficiently;however,high iodine levels can inhibit the growth of vegetables.The toxicity effects of different iodine forms are in the following order:Ⅰ^-＞CH₂ICOO^-＞IO₃^- except for water spinach（the toxicity of iodine is:CH₂ICOO^-＞I^-＞IO₃^-）.Iodine uptake by vegetables was enhanced with the iodine addition,and the respective effects of iodine uptake by vegetables are: I^-＞CH₂ICOO^-＞IO₃^-.The capacity of iodine-enrichment and endurance of iodine toxicity varies in different genotypes of pakchoi,of which Suzhouqing and JiaxingAijiaoqing etc.possessed greater capacity and stronger endurance and could be recommended as iodine-enrichment vegetables.2.The hydroponics experiments showed that the uptake rate of iodine increased sharply in a short time（＜60 min）,then decreased slowly with the time.Under low iodine concentration（0-0.5 mg/L）,the relation of uptake rate of iodate and iodate concentration was exactly suited to the characteristics of Michaelis Equation,which indicated that the iodate may be active absorbed by vegetable under low concentration.The uptake rate of iodine was linearly related with the iodine concentration when the concentration is higher than 0.5 mg/L,which indicated that iodine is passive absorbed by vegetable.The content of iodine in edible parts of vegetable increased in the first week then decreased with the incubation time when the exogenous iodine was added once only,and the content of iodine in vegetable increased steadily when the iodine concentration was preserved constantly.The cholrine added in solution decreased the uptake rate of iodine at low concentration of iodine（＜0.5 mg/L）,but the effect of chorine became weak with iodine concentration increasing.3.The isothermal curves of iodine adsorption on three garden soils could be described by either Langrnuir or Freundlich equation(r＞0.97^**) for each equation.As compared with the iodide,the iodate could be easily adsorbed by soils;and the REQ （red soil developed on Quaternary red earths（clayey,kaolintic thermic plinthite Aquult）） adsorbed more I^- and IO₃^- than the IS（Interceptisol soil） and the AS （alluvial soil）.The distribution coefficient（k_d） of iodine in the soils decreased exponentially with increasing iodine loading.4.In the pot soils,the iodide was easily adsorbed by pakchoi,and caused more toxic to vegetable,the rate of iodine loss in soil was higher as compared with the iodate. The iodine bioavaibility in AS was the strongest but the soil iodine persistent was the shortest among three tested soils,and the REQ showed the polar trend to the AS.¹²⁵I introduced into the soil inclined with the soil depth,but most of the applied ¹²⁵I remained in the surface layer and lower of ¹²⁵I moved downwards and outwards.The ¹²⁵I,adsorption in the soil and absorption in the plant,could be translate into gaseous state and released into the air.5.In the pot experiment,the toxicity of iodine and iodine concentration in tissues were much greater for plants grown with KI than with iodine fertilizer composed of seaweed in the first cutting,and the contrary trend was showed in the second cutting. The content of iodine in edible part of vegetable was as following order:Chinese cabbage＞lettuce＞carrot＞tomato,and the endurance to iodine toxicity was showed as:carrot＞Chinese cabbage＞lettuce＞tomato.The distribution of iodine in different parts of vegetables（Chinese cabbage,leetuce,tomato） was root＞leaf＞stem＞fruit, but the iodine content of carrot shoot was much higher than the earthnut.The residual iodine in soil decreased with the increasing in growth time.The content of iodine applied with KI decreased by 41.5%-58.0%,whereas,iodine fertilizer composed of seaweed decreased to 56.0%-69.0%.As compared with the pot without vegetable,the pot with vegetables has much greater loss rate of soil iodine.6.In the field experiments,the iodine in the edible parts of vegetable increased with the increasing iodine addition in soil.Among these tested vegetable,the leaf vegetable was the type of strongest capability in iodine enrichment,then was stem vegetable,the fruit vegetable was the most weak to the iodine accumulation.Except the soybean,the iodine in edible parts of vegetable decreased with the grow time. Under two different application technique（root application and ex-root application）, soil iodine root application was more favourable to iodine accumulation in vegetable, of which the distribution of iodine in leaf,stem and fruit vegetable was showed as: root＞leaf＞stem＞fruit,but the iodine distribution in root vegetable was showed as: earthnut＜shoot.Whreas with iodine ex-root application（spraying to the leaf）,the iodine content of leaf was the highest,then was stem,and the iodine accumulation in fruit and root was the minimum in all these tested vegetables.7.Water soluble iodine of vegetable mainly consists of I^-,which was 66.7%of total water soluble iodine.Iodine associated with protein was the main form of organic iodine,with the amounts to 22.43%of total iodine of vegetable.The distribution of iodine in the subcell ofpakchoi showed that iodine was mainly present in soluble part of cell accounting for 54.8%-63.9%,with the iodine addition increasing,the proportion of cell wall had a upward tendency.In root cell,iodine combins with fibrous tissue,in stem and leaf cell,iodine consists in chloroplast.更多还原