| Radioactive iodine in the environment can enter into our bodies through air, water, food and so on, but since we mainly live on plant products and food from animals is also indirectly from plants. However, people's knowledge of iodine is still not enough for the reason that mechanisms of migration, transformation, accumulation, and toxicity of iodine in ryegrass. Effects of iodine stress on physiological and biochemical properties and nutrient uptake of ryegrass were investigated. The main results are:1. While compared with the growth indicators, all morphological indicators of ryegrass in red paddy soil or stragnogleyed paddy soil at first increase and then decrease with iodine concentration in increase. Morphological indicators are smaller than the control when the level of iodine is the highest. Meanwhile, ryegrass grows differently in different soils under iodine stress, that is, ryegrass grows better in stragnogleyed paddy soil than those in red paddy soil, just as those indicators show. This is chiefly because with more organic matter, higher pH and CEC in comparison with red paddy soil, stragnogleyed paddy soil has a capacity of mitigating toxicity of iodine. Besides, the suppression level of iodine in red paddy soil is 160 mg/kg sooil and it's 320 mg./kg in Stragnogleyed paddy soil. The level of chlorophyl of leaves of ryegrass growing in both kinds of soils at first increase and then decline, which is similar to results of growth indicators.2. The variation range of the relative activity of SOD, CAT, POD and MDA were different between two kinds of soils. The SOD, CAT, POD contents in ryegrass at first increase and then decrease with increasing iodine concentration whereas this is opposite to the case with MDA. And those contents of SOD, CAT, POD in the group containing the most iodine are always lowerer than the control. With iodine addition, there is negative correlations between activity of SOD, POD, CAT and contents of MDA in both types of soils, and when compared with activity of CAT, the correlation between activity of SOD, POD and contents are stronger. They possibly contribute more to reduction of contents of MDA than CAT.. |
