Effects of current velocity and substrate composition on growth of Texas wildrice (Zizania texana)

Zizania texana Hitchc., an endangered macrophyte has declined in number during the past 50 years. To determine the effects of substrate composition and current velocity on plant growth, plants were grown in pots containing either fine or coarse sediment at three sites in Spring Lake, Hays Co., TX. Each site was similar in depth but differed in current velocity. Plants were allowed to grow for 6 weeks and then harvested. Growth was greater on fine sediments. There was significant interaction between flow and sediment with respect to aboveground biomass and stem density and, there was significant flow effect on leaf length and stem density. Stem density was greater in fast flowing water (0.40-0.49 m s(-1)) than either moderate (0.12-0.24 m s(-1)) or slow flowing (0.05-0.12 m s(-1))water. The decline in Zizania texana population can be attributed, in part, to physical changes to Zizania texana habitat.