伊乐藻和苦草对硝氮胁迫的响应

利用水族箱研究了伊乐藻和苦草对0~200 mg.L-1硝氮胁迫的急性生理生化反应.结果表明:两者的现存量在0<硝氮25 mg.L-1时,均明显正增长,苦草的生长好于伊乐藻;在硝氮为100~200 mg.L-1时,对其生长有不很严重的抑制.在硝氮≤25 mg.L-1时,伊乐藻的净生产力变化较小,苦草的净生产力则随着硝氮浓度的增加而缓慢增加,之后两者均缓慢下降;呼吸作用均无明显变化.随硝氮浓度的增加,两者的叶绿素含量在波动中缓慢下降,敏感性较低;两者的可溶性蛋白浓度均为单峰曲线,伊乐藻和苦草的高峰值分别在硝氮为100和25 mg.L-1时.SOD和POD活性的变化总趋势相近,随着胁迫浓度增加而增加,但在高浓度和较长时间胁迫下,其活性下降,POD活性比SOD更容易下降.

Responses of Elodea nuttallii and Vallisneria natans to the Stress of Nitrate

Acute physiological and biochemical responses of Elodea nuttallii and Vallisneria natans to external NO-3-N(0~200 mg·L-1) were studied in an aquarium experiment.When NO-3-N] was among 0~25 mg·L-1,standing crops of the plants increased markedly compared to the control.V.natans grew better than E.nuttallii.When NO-3-N] was among 100~200 mg·L-1,the plants were not inhibited very seriously.When NO-3-N]≤25 mg·L-1,net productivity of E.nuttallii changed a little,while net productivity of V.natans increased slowly with increasing concentration of NO-3-N,and then both of them decreased slowly.Respirations of the plants didn't change obviously.Chlorophyll contents of the plants decreased wavily and slowly with increasing concentration of NO-3-N,and were weak sensibility to nitrate.The curves of their soluble protein concentrations were single peak curves.The peak values of E.nuttallii and V.natans were at 100 and 25 mg·L-1 NO-3-N,respectively.The change trends of POD(peroxidase) and SOD(superoxide dismutase) activities were similar.Activities of the two kinds enzyme increased with increasing concentration of NO-3-N,but decreased when concentration of NO-3-N was high and experiment lasted long.The activity of POD decreased more easily than that of SOD.