几种蔬菜对外源碘的吸收与积累特性

在盆栽条件下研究了小白菜、芹菜、辣椒和萝卜4种蔬菜对2种外源碘(海藻固体碘肥和KI)的吸收与积累特性.结果表明:蔬菜体内的碘含量均随外源碘浓度的提高而逐渐增加;不同蔬菜种类对碘的吸收与积累能力存在较大差异,叶菜类的小白菜对碘的积累能力最强,其次为茎菜类的芹菜,而根菜类的萝卜和果菜类的辣椒吸收与积累碘的能力较弱;碘在蔬菜体内的分布一般为根>叶>茎>果实,但萝卜地下块根的碘含量低于地上部分.低浓度碘处理(0～25mg.kg-1)对蔬菜生长没有明显的影响,但高浓度的外源碘(≥50mg.kg-1)对蔬菜生长有抑制作用,导致蔬菜生物量减少.不同蔬菜对碘的敏感反应表现为辣椒>小白菜>芹菜>萝卜.与海藻固体碘肥相比,KI处理的第1茬蔬菜生物量下降明显(P<0.05),而2种外源碘对第2茬蔬菜的生长均无显著影响.蔬菜对2种外源碘的吸收和积累效果同样存在很大差异(P<0.05),第1茬蔬菜对KI的吸收能力强于海藻碘肥(P<0.05),第2茬蔬菜对KI的吸收量迅速下降,而对海藻固体碘肥的吸收下降不明显,说明海藻固体碘肥比KI具有更长的持效性.

Characteristics of iodine uptake and accumulation by vegetables

With seaweed iodine and KI as exogenous iodine sources, a pot experiment was conducted to study the characteristics of iodine uptake and accumulation by pakchoi cabbage, celery, capsicum, and radish. The results showed that the iodine content in the edible parts of test vegetables increased with increasing amount of exogenous iodine, but the iodine accumulation rate differed with the kinds of vegetables, in the order of pakchoi > celery > radish > capsicum. The majority of iodine was accumulated in roots, with lesser amount transferred to shoots. The distribution of iodine in vegetables was commonly in the order of root > leaf > stem > fruit, but the iodine in radish is lower in its rhizome than in its shoot. Low concentrations (0-25 mg x kg(-1)) of exogenous iodine had little effects on the growth of vegetables, while high concentrations (> or = 50 mg x kg(-1)) of it had inhibitory effects, resulting in a decreased vegetable biomass. The sensitivity of test vegetables to the adverse effect of exogenous iodine was in the order of capsicum > pachoi > celery > radish. Compared with seaweed iodine, KI decreased the biomass of first cutting significantly (P < 0.05), but for the second cutting, little difference was observed between these two iodine sources. The uptake and accumulation of these two iodine sources by vegetables also differed with cuttings, i.e., the first cutting vegetables absorbed more KI, while the second cutting vegetables absorbed more seaweed iodine (P < 0.05), suggesting that seaweed iodine had a longer efficacy than KI.