[Alleviation Effects of Exogenous Melatonin on Ni Toxicity in Rice Seedings].

The alleviation effect of exogenous melatonin (MT) on Ni toxicity in rice seedings was investigated. The results showed that low concentration of Ni stress (10, 50 µmol·L-1) had little effect on the growth of root of rice seedings, while higher concentration of Ni stress (100-1000 µmol·L-1) significantly inhibited the growth of rice root. Compared with the control treatment, the addition of 100 and 1000 µmol·L-1 Ni would decrease the total length and surface area of root by 63.3%-98.0% and 56.9%-96.3%, respectively. The results showed that addition of exogenous melatonin had a positive effect on the growth of rice seedings under Ni stress. This kind of positive effect was even more obvious in the root of rice seedings. The total length of rice root decreased by 58.4%-83.8% at Ni concentration of 100 µmol·L-1, whereas it decreased by only 8.7%-29.1% when 100 µmol·L-1 Ni and 10 µmol·L-1 MT were added, compared with the control treatment. The addition of exogenous melatonin had significant alleviation effects on oxidative stress in rice seedings caused by Ni. Compared with the 100 µmol·L-1Ni treatment, addition of 10 µmol·L-1 exogenous MT could significantly decrease the production rate of O2-· by 43.2%-50.2% and the relative electrolytic leakage by 25.7%-31.6%, whereas increase the activities of CAT by 21.9%-33.7% and the soluble protein content by 82.6%-84.6%. The results suggested that application of exogenous melatonin could effectively alleviate the toxic effects of Ni on rice seedings.

[Effects of exogenous melatonin on accumulation and chemical form of Cd in rice]. / è¤ªé»‘ç´ å¯¹æ°´ç¨»é•‰ç§¯ç´¯åŠå ¶åŒ–å­¦ç»“åˆå½¢æ€çš„å½±å“.

Effects of exogenous melatonin on accumulation and chemical form of Cd in rice seedlings were investigated. The results showed that Cd stress significantly decreased the biomass of shoots and roots, and the chlorophyll content in rice leaves. The addition of exogenous melatonin could remarkably increase the biomass of rice and significantly decreased Cd content in the shoots and roots. At Cd concentration of 5 Μmol·L-1, addition of 20 Μmol·L-1 exogenous melatonin could decrease Cd content in rice shoots and roots by 48.4% and 16.9% respectively, compared with the control. When the concentration of exogenous melatonin rose to 100 Μmol·L-1, Cd content in rice shoots and roots decreased by 67.5% and 47.9% respectively. Furthermore, the addition of exogenous melatonin obviously decreased the Cd-translocation efficiency of rice seedlings. When the Cd concentration was 20 Μmol·L-1, addition of 20 and 100 Μmol·L-1 exogenous melatonin could decrease the Cd-translocation efficiency by 24.4% and 46.8% respectively. The chemical form of Cd in rice seedlings was analyzed by using sequential extraction. The results showed that exogenous melatonin addition increased the proportion of NaCl-extractable Cd, while decreased the proportion of ethanol-extractable Cd and water-extractable Cd in rice seedlings. It was suggested that the addition of exogenous melatonin could promote the transfer of Cd from strong to weak mobility form, thereby reducing the uptake and transport of Cd in rice seedlings.

[Phenols pollutants in soil and shallow groundwater of a retired refinery site].

To study the distribution of phenol compounds in a retired refinery site, 21 soil sampling sites and 8 shallow groundwater wells were investigated. The results showed, shallow unconfined groundwater of the site was in a serious pollution situation and the phenols concentration was much higher than quality standard for ground water. Confined water sample was slightly contaminated by phenols and the total quality was good. Approximately half of the area was heavily polluted by phenol compounds. According to the retired refinery layout, the phenols pollution distribution in shallow groundwater and soil exhibited the regional similarity. The highly contaminated area was production workshop, oil tank and plant storage. Horizontal diffusion of pollutants was not serious. Vertical diffusion of pollutants was different, and a site with pollutant diffusion was deeper than ten meters. The 2-chlorophenol, 2-nitrophenol, 2,4-xylenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol, 2,4-dinitrophenol and 2-methyl-4,6-dinitrophenol in typical soils were analyzed by GC/MS. It showed that concentrations of seven phenol compounds were 0.01-232.96 mg x kg(-1), and the concentrations of 2,4-dinitrophenol and 2-methyl-4,6-dinitrophenol were high.