蔬菜吸收不同形态外源碘的动力学特性

采用水培法,研究了两种蔬菜(小白菜和芹菜)对两种不同形态碘源(I-,IO-3)的吸收和积累特性.结果表明:供试蔬菜吸收碘的速率表现为在短时间(＜60 min)内迅速增加,随着时间的延长蔬菜对碘的吸收速率逐渐下降;在低浓度范围内(0.01～0.50 mg/L)蔬菜对IO-3的吸收速率与碘浓度变化曲线符合饱和吸收动力学特征(表现为遵循酶学方程),进一步研究表明,解偶联剂2,4-二硝基苯酚(DNP)对低浓度(＜0.50 mg/L)下蔬菜IO-3吸收速率具有明显的抑制作用,说明两种蔬菜对低浓度的IO-3可能存在主动吸收,而在高浓度范围内(0.50～10.0 mg/L),蔬菜对碘的吸收速率随着碘浓度的提高呈现直线上升的趋势.两种蔬菜相比,在同样条件下芹菜对碘的吸收速率明显大于小白菜.蔬菜可食部分中碘的含量随着碘浓度的提高而增加,在一次加碘条件下表现为先增加后降低的趋势,而在持续加碘条件下蔬菜中碘的含量在整个处理期间表现为不断增加; Cl-的添加对低浓度下蔬菜碘的吸收具有明显的抑制作用,而随着碘浓度的提高Cl-的抑制作用逐渐减弱.供试蔬菜对碘的富集系数随碘浓度的提高而降低,碘在蔬菜不同器官的分配次序表现为根＞叶＞茎.

Dynamic characterization of iodine uptake in vegetable plants

Hydroponics experiment was carried out to investigate iodine (iodide or iodate) uptake in celery and Chinese cabbage. Iodine uptake in both plants increased rapidly within a short time treatment (<60 min) and then decreased gradually. With low iodine concentration (0-0.50 mg/L) treatments, characteristics reminiscent of Michaelis-Menten kinetics was observed via relationship of concentration of iodate or iodate and the the iodine uptake rate. Iodate uptake was inhibited by oxidative phosphorylation inhibitor 2,4-dinitrophenol when the plants were treated with less than 0.50 mg/L iodate, whereas no significant inhibit was observed and the iodine uptake rate was linearly correlated to the iodine concentration when iodate concentration was above 0.50 mg/L, which suggested that plant can actively uptake iodate when under low concentration. As compared to Chinese cabbage, celery showed a greater iodine uptake. The iodine content in the vegetable edible parts increased in the first week then decreased as the iodine was added only once at the beginning, whereas the iodine content of edible parts of vegetable increased constantly when continuously supplied with iodine. When treated with low iodine concentration (<0.50 mg/L), iodine uptake in both plants were reduced by chlorine, but no significant effect of chlorine on iodine uptake in the plants treated with high iodine concentration. The iodine accumulation coefficient in both plant was decreased when the iodine concentration in the media increased. The iodine distribution in both plants was root>leaf>stem.