镉胁迫对满江红-鱼腥藻共生体供氮能力的影响

在实验室条件下,以土壤铵态氮、硝态氮、可溶性有机氮及可溶性总氮含量变化为指标,研究了镉胁迫下满江红-鱼腥藻共生体对稻田供氮能力的影响.当土壤中镉浓度为0.3 mg·kg-1时,满江红-鱼腥藻共生体对镉的蓄积量较少,土壤中铵态氮、硝态氮、可溶性有机氮及可溶性总氮含量与对照组无显著差异.当土壤中镉浓度≥1.0 mg·kg-1时,随土壤中镉浓度的增加和处理时间的推移,满江红-鱼腥藻共生体体内的镉含量逐渐增加,土壤中硝态氮、可溶性有机氮及可溶性总氮含量逐渐下降,而铵态氮含量先上升后下降.研究结果表明高浓度的镉胁迫导致满江红-鱼腥藻共生体对土壤的供氮能力显著下降.

Effects of Cd stress on nitrogen supply ability of Azolla imbricata-Anabaena azolla symbiosis

The nitrogen supply ability of Azolla imbricata -Anabaena azolla symbiosis under Cd stress was investigated in laboratory, using changes of NH₄⁺-N, NO₃^--N, soluble organic nitrogen (SON) and total soluble nitrogen (TSN) contents in the paddy soil as indicators. When the concentration of Cd in the soil reached 0.3 mg·kg^-1, Cd bioaccumulation in the symbiosis was not significant and the above mentioned parameters in soil did not change significantly during the experimental period. When Cd concentration in soil was above 1 mg·kg^-1, Cd bioaccumulation in the symbiosis increased gradually with both increases of Cd concentration in the soil and duration of Cd treatment. At the same time, NO₃^--N, SON and TSN contents decreased gradually, while the ammonium content increased in the early period of experiment and then decreased rapidly. These results indicated that the nitrogen supply ability of A. imbricata-A. azollae symbiosis to soil decreased significantly under higher concentrations of Cd stress.