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Bulletin of Botanical Research ›› 2018, Vol. 38 ›› Issue (5): 653-660.doi: 10.7525/j.issn.1673-5102.2018.05.003

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Effects of Ammonium Nitrogen on Physiological and Ecological Characteristics of Kandelia obovata under Cadmium Stress

LI Rong-Yu, QIU Guo-Yu, SHEN Xiao-Xue, CHAI Min-Wei   

  1. School of Environment and Energy, Shenzhen Graduate School, Peking University, Shenzhen 518055
  • Received:2018-04-30 Online:2018-09-15 Published:2018-08-31
  • Supported by:
    The National Natural Science Foundation of China(31400446);Program of Science and Technology of Shenzhen(JCYJ20150331100946599,JCYJ20160330095549229)

Abstract: The heavy metal pollution and excess input of nutrient elements become two important environmental problems in mangrove forest. The ecological risk of cadmium(Cd) is relatively high, and ammonium nitrogen(NH4+-N) is the main speciation of nitrogen in sediment of mangrove. In order to clarify the growth and physiological characteristics of Kandelia obovata under combined stresses of Cd and NH4+-N, pot experiments were conducted. Plant growth, leaf photosynthetic parameters(photosynthetic rate(Pn), stomatal conductance(Gs), intercellular CO2 concentration(Ci) and transpiration rate(E)), leaf malondialdehyde(MDA), leaf soluble sugar, and root activity were determined. The results showed that:(1)Plant growth and leaf transpiration rate(E) of K.obovata decreased under single Cd stress, with root activity to be reduced under higher single Cd stress; (2)Under Cd stress, low concentration of NH4+-N significantly improved growth of root, but did not significantly improved growth of aboveground part, and leaf photosynthesis(Pn, Gs and E); while high concentration of NH4+-N significantly reduced plant growth, and leaf photosynthesis(Pn, Gs and E); (3)Under Cd1 treatment, root activity first increased and then decreased with increasing NH4+-N concentration; while reduced root activity were shown under Cd2 and Cd3 treatments with NH4+-N supply; (4)Under Cd stress, low concentration of NH4+-N did not significantly reduce content of malondialdehyde(indicative of oxidative damage) and soluble sugar(indicating osmotic adjustment), while high concentration of NH4+-N significantly reduced the content of MDA and soluble sugar. Therefore, the lower concentration of NH4+-N can alleviate the Cd toxicity to root, with limited emission on aboveground part; while high concentration of NH4+-N and Cd combined stress would have a synergistic effect to aggravate Cd toxicity to K.obovata.

Key words: heavy metal, nutrient element, mangrove plant, photosynthesis

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