当前世界环境

镉是污染最严重的草本、有毒重金属之一。虽然它不是植物生长所必需的，但它只是被根吸收并转移到气生器官。植物中镉的聚集是人类和动物食物中毒的主要来源。镉是一种自然存在于地壳中的元素。纯镉是一种软如银的金属。通常镉在环境中不是作为游离金属存在的，而是与其他元素结合，如氧化镉、氯化镉或硫化镉和硫酸镉等。硫化镉用作塑料中的颜料。造成环境中镉污染的主要因素有:
煤炭和家庭垃圾的燃烧以及从矿山中提取金属导致环境中镉的增加。
house- waste and industrial waste waters introduce cadmium in potable waters, and under ground waters.
chemical fertilizers specially phosphor have sufficient amount of cadmium. Fertilizers made from phosphate minerals is also one of the source of cadmium pollution. Agricultural lands in many parts of the world are polluted by cadmium as a result of the use of phosphate fertilizers for long time. In this study the effects of cadmium chloride on a number of agricultural Brassica napus kinds is under taken, with following points. 1. Cadmium effect on sprouting in petri dishes. 2. The study of cadmium effect on the growth of Brassica napus embryo in Hogland food solution and the selection of B. napus types which are sensitive and resistant to cadmium chloride. 3. The effect of cadmium chloride is considered in respect of these aspects: Variation in amount of chlorophyll from leaves. 4. The study of role of cadmium in roots and aerial parts of the plant. 5. The study of amount of cadmium in the seeds due to green house cultivation of two sensitive and resistant varities Brassica napus kinds.