| Cadmium is one of the most dangerous heavy metals to both plants, animals and the people, and its contamination in soil has turned into one of the most troublesome issues agriculture and environment worldwide. It is one of the most efficient approaches to developing varieties or genotypes whose Cd accumulation have obvious difference so as to alleviate health risks associated with Cd exposure and guarantee food safety and make full use of natural resources and bring under control the polluted soil. By pot cultivation experiment, this investigation was carried out to study the genotypic differences of Cd absorption and accumulation of the oilseed rape and pakchoi, whose affinities were close, in two growth periods, and analysize the effect of different Cd concentrations on the growth and the characters of physiology. Simultanously, it was simply discussed that the effect of Cd on the soil. The major results were summarized as follows: 1. Cadmium stress significantly inhibited the growth of the oilseed rape and pakchoi and the increase of biomass. The symptoms of Cd toxicity in shoot were plant shortening and weakening, the leaves turning yellow and the vein white, and the slow speed of coming into leaf. The restraint of Cd in low concentration on plant height and biomass was not significantly, while it was significantly in high Cd. 2. In the seven chosen materials, Cd content of the plants increased greatly with Cd treated levels; but although the shoot Cd concentration decreased slightly with an increase in growth period (28-56 days), Cd uptake was still increasing promptly. Cd can be absorbed well by Pakchoi C, Cd concentration of which was more 2 times of the others, whereas done badly by oilseed rape F. If the relatively biomass is used to express Cd tolerance, pakchoi C and oilseed rape F will show relatively good Cd tolerance. However Cd tolerance is not linked to Cd content. 3. Respectively choose two genotypes of pakchoi and oilseed rape which have obvious difference to the Cd react (Jinyou 4 and Zajiao F-3, Cuibao and Qingbang), and study the effect of Cd on their index of physiology and biochemistry. The results showed: With the increase of the Cd treated concentration, the photosynthesis rate of plant leaf showed the declining trend. High concentration of Cd significantly inhibited the photosynthesis rate. But there is not very obvious difference among the genotypes. The chlorophyll content of the leaves of oilseed rape and pakchoi considerably reduced with the increase of Cd levels. In this experiment, the soluble sugar content in the shoot of oilseed rape Zajiao F-3 and pakchoi increased differently. The increase of Zajiao F-3 was more evident. However, Jinyou 4 showed a decreased tendency as Cd level exceeded 10mg/kg. The effect of Cd on permeability of membrane of oilseed rape and pakchoi leaf was apparent. When the Cd concentration increase, the permeability of membrane increased too, which exceeded about 50% of CK when Cd concentration was 100mg/kg. Among them, Jinyou 4 increased most obviously, meanwhile Zajiao F-3 did most slightly. Pakchoi was that the increase of Cuibao was less than Qingbang. The activity of SOD and POD in the leaves of oilseed rape and pakchoi rose with the intension of stress increasing in some range. The increase of the activity of POD of Zajiao F-3 was more than that of Jinyou 4, and POD activity was always more than Jinyou 4 under all Cd levels. Pakchoi was that the activity of POD of Cuibao was more than Qingbang. SOD activity of oilseed rape and pakchoi increased slightly under 5mg/kg Cd concentration. However, SOD activity of all plants showed obvious declining trend with the increase of the Cd treated concentration (20~100mg/kg). Among them, Zajiao F-3 decreased most slightly. The activity of PPO submitted obviously rasing trend with external Cd levels, the increase of which of Zajiao F-3 was less than the other. Three enzymes showed different extent positive protect function, whose activity change was accordance to the tolerance to Cd. This indicated the keeping and raising of the activity of POD,PPO and SOD was one of the foundation of the tolerance to Cd stress. 4. The results of effective Cd in the soil showed that lime soil can obviously inhibit the... |
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