Abstract: Microcystis aeruginosa, Scenedesmus obliqnus and Chlorella vulgaris were cultured in the cultured water of six beauty hydrophyte species (Iris pseudacorus, I. sanguinea,  Pontederia cordata, Jussiaea repens,  Hydrocleys nymphoides, and Pistia stratiotes) to study the effects of the cultured water on the growth of the three algae species. The results showed that the cultured water of the six hydrophyte species had selective allelopathy on the three algae species, showing strong inhibiting effect on both M. aeruginosa and S. obliqnus. After culturing for six days, the inhibiting rate of the cultured water of the six hydrophyte species on the growth of M. aeruginosa was 31.22%-96.53%,and,except for J. repens,the cultured water of the other five hydrophyte species had an inhibiting rate exceeding 70%. The inhibiting rate of the cultured water of the six hydrophyte species on the growth of S. obliqnus was 23.15%-77.25%, and that on the growth of C. vulgaris ranged from  -26.07% to 75.70%. The cultured water of P. stratiotes, P. cordata, and I. sanguinea had stronger inhibiting effect on the growth of C. vulgaris, but the cultured water of I. pseudacorus and J. repens promoted the C. vulgaris growth at lower concentration while inhibited the C. vulgaris growth at higher concentration. The cultured water of H. nymphoides promoted the growth of C. vulgaris. The inhibiting effect of the cultured water on the growth of the three algae species increased with increasing culture time. The inhibiting effect of the cultured water of the six hydrophytes on the growth of M. aeruginosa was in the sequence of H. nymphoides＞I. pseudacorus＞P. cordata＞P. stratiotes＞I. sanguinea＞J. repens, that on the growth of S. obliqnus was P. cordata＞I. sanguinea＞I. pseudacorus＞H. nymphoides＞J. repens＞P. stratiotes, and the inhibiting effect on the growth of C. vulgaris was P. stratiotes＞P. cordata＞I. sanguinea＞I. pseudacorus, J. repens＞H. nymphoides. The results indicated that the test six hydrophyte species had definite extension significance in controlling the algal bloom in landscape water body in urban area.

Key words: respiratory quotient (RQ), calcification, Crassostrea gigas,  O/N.