The present invention includes a container unit and a plant extending unit. The container unit has a bottom plate, a surrounding wall and an accommodation space. The accommodation space is located between the bottom plate and the surrounding wall. The plant extending unit watertightly penetrates through the bottom plate and extends toward the accommodation space with a height. The plant extending unit has an extension channel which communicates with the accommodation space and the environment. The accommodation space is configured to accommodate a hydroponic fluid and a planting structure, in which the level of the hydroponic fluid is lower than the height of the plant extending unit. The planting structure has a root part, a stem part and a flower leaf part. At least one of the root part and the stem part is immersed in the hydroponic fluid. At least one of the stem part and the flower leaf part is extended to the environment through the extension channel. Thereby, a hydroponic system that allows plants to grow downward is formed. The hydroponic system that allows plants to grow downward of the present invention is novel and has the advantages of dual use of daylighting and plant lighting for energy saving.本發明係包括一容器單元及一植栽伸出單元。容器單元具有一底板、一圍牆及一容納空間，容納空間位於底板及圍牆之間。植栽伸出單元水密穿透底板，並朝容納空間內延伸一高度；植栽伸出單元具有一伸出通道，伸出通道連通容納空間及外界。容納空間容納一水耕液及一植栽結構，水耕液低於植栽伸出單元之高度；植栽結構具有一根部、一莖部及一花葉部；根部、莖部的其中至少一者係浸植於水耕液內，莖部、花葉部的其中至少一者係經伸出通道伸出至外界，構成可倒種植栽之水耕系統。故，本案兼具可倒種植栽之水耕系統別具新穎性，及採光及植栽光照兩用相當節能等優點。
