Utilization of Soybean and Adzuki Bean as Bioindicator of Cadmium Pollution
Date Issued
2004
Date
2004
Author(s)
Shiow-Lian, Chang
DOI
zh-TW
Abstract
In recent years, waste water or other waste of the industry has caused serious pollution in farm soil in Taiwan. Monitoring of the water and soil pollution usually relied on expensive instrument and was not convenient. Therefore, we consider to use plants as a tool to monitor the pollution.
By treating the soybean and adzuki bean in water culture, twenty cultivars were screened for their specific symptoms against 1ppm cadmium. Results showed that all the plants expressed reddish brown symptom, even though there was a time difference. According to the criteria of speed of symptom expression, interference from natural pigment and the popularity of the cultivar, we select four cultivars including soybean ST4, SK6, adzuki bean AK3 and AK7 for further studies.
When eight heavy metals were treated to these four cultivars, only cadmium produced the reddish brown symptom on them. They will express such a symptom even at concentration of 0.1ppm in water culture. At higher concentration, the plants reveal such a symptom faster.
Because the Hoagland solution can not be adjusted for higher pH, Peter’s fertilizer was used instead to test the effect of pH on cadmium. All four cultivars were treated with 3 levels of pH. We found that soybean ST4 and SK6 expressed symptoms fastest in pH 6.2. The adzuki bean AK3 and AK7, however, died in pH4.7 and pH6.2. The results suggest that Peter’s fertilizer is only suitable for the soybean, not for adzuki bean.
When young seedings of these four cultivars were transplanted onto man-made cadmium-polluted soils, they can express the symptoms at concentrations as low as 1ppm. The higher the concentration the faster the plants reveal such a symptom.
When seeds of these four cultivars were directly sown in the man-made cadmium-polluted soils, only soybean SK6 and adzuki bean AK7 showed the tendency that at higher concentration, the symptoms appear faster. Hower, soybean ST4 and adzuki bean AK3 did not fit the rule. Some of them did not express the symptoms very well at higher concentration. Results of this experiment suggest that direct sowing is suitable only for adequate concentration, but not for high level of pollution.
The effect of soil pH on Cd symptom expression was studied by transplanting the seeding to man-made cadmium-polluted soils at 3 pH levels. Result showed that soybean ST4, adzuki bean AK3 and AK7 expressed symptom in three days at pH4.7, while soybean SK6 expressed symptoms in four days. At pH5.6 and pH6.2, all four cultivars did not show the symptoms after ten days. These results suggested that the acidity of the soil will affect the symptom expression. The higher the soil pH, the slower the symptom will appear.
Seven contaminated field soils were sampled from farms in Chang-Hwa county. The young seedings of four cultivars were transplanted onto them. Results showed that all the cultivars expressed the symptom, even thought the symptoms appears several days later as compared with the man-made cadmium-polluted soil. The main reason is that the pH of the soil from the field is higher than that of the man-made soil.
Subjects
紅豆
鎘
大豆
Cadmium
Soybean
Azuki bean
Type
other