青菜(Brassica chinesis L.)对碘动态吸收的同位素示踪

碘是合成甲状腺激素不可缺少的元素，食物中严重缺碘可以导致人体中甲状腺功能的失调。利用同位素示踪技术研究了青菜在水培条件下对碘（¹²⁵I）的吸收和富集特征，并在此基础上讨论了植物对碘吸收的生物学机制。研究结果表明，青菜根部能迅速吸收¹²⁵I并向地上部分输送，青菜各部位¹²⁵I的比活度大小顺序是根>茎>叶；青菜茎对碘的吸收量白天大于夜晚，青菜叶对碘的吸收夜晚大于白天；青菜植株不同部位叶片碘含量存在差异，上部嫩叶中¹²⁵I　高于下部叶片，说明青菜中¹²⁵I　的富集特征是植物对碘主动吸收和被动吸收共同作用的结果。青菜培养时间经过120h后，¹²⁵I　的消耗途径主要是作物的吸收和自然挥发，¹²⁵I　的放射性衰变丢失的量相对较少。研究为培育含碘作物提供了科学依据。

Dynamic absorption of iodine-125 in Chinese cabbage (Brassica chinesis L.)

Iodine has been long known as an indispensable element in the synthesis of thyroid hormones. Severe iodine deficiency in diet leads to iodine deficiency disorders in humans. Here we propose a new method of iodine supply by cultivating iodized crops. We studied the dynamic absorption pattern of ¹²⁵I by Chinese cabbage (Brassica chinesis L.) from liquid media, using the isotope tracer method. The results showed that ¹²⁵I is absorbed quickly by roots and generally transported to shoots. The iodine accumulation capacity in different tissue types ranks as root>stem>leaf. More ¹²⁵I was absorbed during the day than during the night in stems, but opposite in the leaves. Analysis on leaves from different nodes reveals a differential absorption pattern that ¹²⁵I accumulates more in the upper leaves than in the lower leaves. These results suggest that active and passive ¹²⁵I absorption mechanisms may coexist in liquid cultivated Chinese cabbage. After 120 hours, most of ¹²⁵I in the liquid media was absorbed by Chinese cabbage and some was lost through volatilization. This study provides initial scientific basis for cultivating organic iodized crops as an alternative to iodized salt to reduce iodine deficiency.