Effects of cadmium stress on the antioxidant system and chlorophyll fluorescence characteristics of two Taxodium clones
The T.118 and T.406 seedlings showed strong adaptability under Cd concentrations ≤ 50 µM. The mechanisms of photoprotection in T.118 and T.406 differed in high-Cd concentrations.
To explore the physiological response characteristics of Taxodium hybrids to cadmium (Cd) stress and provide basis for screening of Cd-tolerant species, the hydroponic cultivation of T.118 and T.406 seedlings was conducted to demonstrate the effects of Cd stress on seedling growth, antioxidant system, and chlorophyll fluorescence parameters. After 35 days of Cd stress at a concentration ≤ 50 µM, the dry weight biomass of the two clones did not significantly differ from that of the control. T.406 exhibited a significant increase in POD activity compared to T.118 and maintained high SOD activity after exposure to high concentrations of Cd, whereas MDA levels showed little changes. Under low-Cd stress, chlorophyll content and fluorescence parameters remained stable, especially for T.406. Under high-Cd concentration stress, the above parameters were lower than the control, with a more significant decrease in T.118 than in T.406. The non-photochemical quenching coefficient (NPQ) of both clones increased with increasing Cd concentration. T.118 showed a greater increase than T.406, particularly under high-Cd concentration stress. The T.118 and T.406 seedlings adapted to low-Cd concentration stress by enhancing their antioxidant enzyme activity to maintain the balance of reactive oxygen metabolism and reduce cellular damage. The photochemical activity of mesophyll cells remained high to maintain photosynthetic capacity and normal seedling growth. T.406 showed stronger resistance to Cd than T.118. T.406 prevented photodamage by promoting the photochemical utilization of the excitation energy and maintaining a strong antioxidant stress ability. Enhancement of heat dissipation capability may be the main photoprotection mechanism of T.118.
KeywordsTaxodium hybrid “Zhongshanshan” Cadmium stress Growth Antioxidant system Chlorophyll fluorescence characteristics
This work was supported by Postgraduate Research and Practice Innovation Program of Jiangsu Province, Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD), the Doctorate Fellowship Foundation of Nanjing Forestry University and Training Programs of Innovation and Entrepreneurship for Undergraduates of Nanjing Forestry University (2015sjcx015). We thank LetPub (http://www.letpub.com) for linguistic assistance during the preparation of this manuscript.
MYL and WHF conceived and designed the experiments. WP, LSQ and ZYF performed the experiments. MYL analyzed the data and wrote the paper. YCG and XYF revised and approved the final manuscript. All authors reviewed the manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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