Eisentoxizität bei Nassreis

水稻铁毒害是由微生物还原铁引起的一种病症，涉及水稻根部对铁的过度吸收及其顶端转运到叶片中。在那里，铁(11)可以通过增加氧自由基的产生而导致氧化应激。胁迫的严重程度及其对水稻的危害主要取决于Fe(II)的含量和发生的时间，以及水稻品种耐性机制的类型和广度。我们假设，环境特定的铁中毒发生条件的时空变化需要不同的适应机制的表达，以及它们与普遍的铁胁迫情况的匹配。对具有代表性的水培水稻品种的适应机制类型和效率的评估如下：(1)耐性品种鉴定：a)不同生育阶段症状表现和组织铁含量；b)59Fe-转运的动态。(2)适应策略的评估：a)策略I(排除)：确定根的氧化能力；b)策略II(转位和分配)：量化木质部和茎组织中的铁和胁迫信号；c)策略III(组织耐受性)：通过自由基清除酶的活性避免氧化胁迫。(3)对不同铁胁迫类型的控制/耐受能力的适应策略的分类。比较评估被认为允许评估和区分低地水稻所需的适应机制，以应对铁中毒发生的不同条件。

Iron toxicity in lowland rice is a condition caused by the microbial reduction of iron and involves an excessive uptake of Fe (II) by the rice roots and its acropetal translocation into the leaves. There, Fe(ll) can cause oxidative stress via an elevated production of oxygen radicals. The severity of the stress and its damaging effects on rive depend mainly on the amount of Fe (II) and the time of its occurrence and on type and extend of rice cultivar's tolerance mechanisms. We hypothesize that the environment-specific spatio-temporal variation in conditions of iron toxicity occurrence requires differential expression of adaptation mechanisms and their matching with prevailing iron stress situations. The type and the efficiency of adaptation mechanisms will be evaluated in representative hydroponically-grown lowland rice cultivars as follows: (1) Identification of tolerant cultivars: a) symptom expression and tissue Fe content at different growth stages; b) Dynamics of 59Fe-translocation. (2) Evaluation of adaptation strategies: a) Strategy I (Exclusion): Determination of the oxidation power of roots; b) Strategy II (translocation and partitioning): Quantification of Fe and stress signals in xylem and stem tissues; c) Strategy III (tissue tolerance): Avoidance of oxidative stress by the activity of radical-scavenging enzymes. (3) Classification of adaptation strategies regarding their effectiveness to control/tolerate different Fe stress types. The comparative evaluation is seen to allow the assessment and differentiation of adaptation mechanisms required for lowland rice to cope with the diverse conditions of iron toxicity occurrence.