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Scientia Silvae Sinicae ›› 2013, Vol. 49 ›› Issue (11): 51-59.doi: 10.11707/j.1001-7488.20131107

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Comparative Analysis of Salix babylonica and Salix matsudana for Their Cadmium Accumulation, Growth and Photosynthesis in Response to Cadmium Contamination

Jia Zhongmin1,2, Wang Li1, Wei Hong1, Feng Hanru3, Li Changxiao1   

  1. 1. Key Laboratory of Eco-Environments of the Three Gorges Reservoir Region of Ministry of Education College of Life Science, Southwest University Chongqing 400715;
    2. Southeast Sichuan Geological Group, Chongqing Bureau of Geology and Minerals Exploration Chongqing 400038;
    3. Chongqing Fengmingshan Middle School Chongqing 400037
  • Received:2012-09-18 Revised:2013-03-05 Online:2013-11-25 Published:2013-11-26

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Abstract:

In this paper, a hydroponic experiment of Salix babylonica and S. matsudana was conducted to evaluate the phytoremediation capability to cadmium contamination. The rooted cuttings were exposed to 0, 5, 10, 20, 50 mg Cd·L-1 for four weeks in a growth chamber. Growth, biomass, photosynthesis and cadmium content distribution in various parts of the plants were measured. It was found that: 1) The tolerance indexes (Ti) (%) based on the dry biomass and growth parameters decreased with increasing cadmium concentration in culture solution. The Ti of S. babylonica and S. matsudana reached 79.30, 73.11 and 98.48, 90.69 in 5 and 10 mg·L-1, respectively. The two species were able to be defined as highly tolerant by a standard of (Ti>60), and S. matsudana had higher tolerance than S. babylonica. 2) The root length and surface area of S. babylonica decreased significantly with increasing cadmium, while the root length, surface area and volume of S. matsudana as well as the root volume of S. babylonica increased firstly, and then decreased. Root average diameter of the two species increased significantly with increased cadmium content. 3) Cadmium inhibited the chlorophyll biosynthesis of developing leaves of S. babylonica and S. matsudana, however had no significant effect on the pigments in mature leaves. The net photosynthetic rate (Pn) of S. babylonica seedlings in 5 mg·L-1 and S. matsudana seedlings in 10 mg·L-1 increased significantly (P<0.05), and then decreased significantly (P<0.05), compared with the control. But the Pn of S. babylonica seedlings in 10 mg·L-1 still had 86.47% of the controlled plants. The stomatal conductance (Gs), transpiration rate (Tr), intercellular CO2 concentration (Ci) of the two species had similar variation patterns to the Pn, but the variations were not significant except in 50 mg·L-1. Cadmium content at which the gas exchange of S. babylonica decreased significantly was lower than that of S. matsudana, indicating that tolerance of S. matsudana was higher than that of S. babylonica. 4) Cadmium accumulation in roots of the two species was higher than in the shoots in 5-50 mg·L-1 of cadmium. The cadmium translocation factor (Tf) of S. matsudana was 0.08-0.51, being 1.71-5.18 times than that of S. babylonica (0.02-0.15). The Cd concentrations in the aerial parts of S. babylonica and S. matsudana cultured in 10 mg·L-1 Cd reached to 130.42 mg·kg-1 DW and 273.72 mg·kg-1 DW, respectively. The results indicated that S. babylonica and S. matsudana had a higher adaptability of growth and photosynthesis to cadmium when Cd content in hydroponics was less than 10 mg·L-1, especially 5 mg·L-1, and thus had a high tolerance to cadmium. The capability of translocation and accumulation in aerial parts of S. matsudana was greater than that of S. babylonica. Therefore the two species hold promise for phytoextraction in cadmium-contaminated areas, especially S. matsudana. However a longer field-scale study on cadmium-contaminated soils is needed before their role in phytoremediation can be confirmed.

Key words: Salix babylonica, Salix matsudana, cadmium, tolerance, accumulation, growth, photosynthetic response

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