Responses of Elodea nuttallii,Vallisneria natans and Potamogeton crispu to Acute stress of PO_4~(3-)-P+NO_3~--N

The changes of the standing crops,productivities,chlorophyll content of Elodea nuttallii,Vallisneria natans and Potamogeton crispu under the acute stress of [NO-3——N+PO3-4-P] are studied by using microcosm systems within 3 days.The results show that when the concentration of [NO-3-N]+[PO3-4-P] is among 0-28.2 mg·L-1,standing crops of the E.nuttallii and V.natans increase markedly,and then decrease when the concentration of [NO-3-N]+[PO3-4-P] exceed 28.2 mg·L-1.While the standing crops of P.crispu always increase when the concentration of [NO-3-N]+[PO3-4-P] is among 0-225.6 mg·L-1.The ability is to fight back the stress of NO-3-N+PO3-4-P was P.crispu E.nuttallii  V.natans.There is no synergistic effect between NO-3-N and PO3-4-P on the three species plants.