Abstract: Field investigation was conducted to study the adaptability of Iris pseudacorus and Canna incida to water depth gradient (10, 30, 50, and 70 cm). It was observed that with the increasing water depth, the tiller numbers of I. pesudacorus and C. incida decreased significantly (P<0.05), but the plant height, leaf length, and leaf width were less affected. Both the chlorophyll content and the root vigor of I. pseudacorus and C. incida decreased with increasing water depth, while the leaf MDA concentration was in adverse. The chlorophyll content, root vigor, and leaf MDA concentration of C. incida differed significantly among different water depths (P<0.05), but only the root vigor of I. pseudacorus had significant difference (P<0.05). Among the chlorophyll fluorescence parameters, the maximal light converting efficiency (F_v/F_m), apparent electron transfer rate (ETR), and photochemical quenching (qP) all decreased significantly with increasing water depth (P<0.05), while the non-photochemical quenching (qN) had a significant increase (P<0.05). The relative electron transfer rate (rETR), potential maximal rETR (rETR_m), light use efficiency (α), and tolerance to intense light (I_k) all decreased obviously with increasing water depth. At water depth 10 cm, the values of all test indices were higher for C. incida than for I.pseudacorus; but at deeper water depths, an opposite trend was observed. It was found that deeper water depth had inhibitive effect on I. pseudacorus and C. incida, and the effect was greater on C. incida. Therefore, it should be kept in shallow water depth when using these two plants for wetland plant remediation in favor of the two plants’ growth. The appropriate water depth for I. pseudacorus and C. incida would be 30-70 cm and 10 cm, respectively.

Key words: Citrus, Ecological distribution, Fuzzy, Decision system