Texas wildrice (Zizania texana Hitchc.) propagule production and survival in outdoor ponds as influenced by water depth and velocity

Abstract

Propagule production (seeds or tillers) of Texas wildrice, Zizania texana Hitchc. (Poaceae), grown in ponds can be manipulated by adjusting water levels and flow rates. Water levels < 0.35 m (1.15 ft) and current velocities < 0.10 m/s (0.33 ft/s) resulted in emergent Texas wildrice (TWR) that flowered and produced seeds and tillers. Water depths > 0.50 m (1.64 ft) and current velocities > 0.15 m/s (0.49 ft/s) resulted in submerged plants that did not flower, but did produce tillers. Tiller production was equal among TWR plants regardless of water depth and current velocities. Survival of TWR was 81% regardless if plants were emergent or submerged. Increasing the number of tillers and tiller root length during the initial planting also increased survival rates. Tillers and seeds can be collected from TWR plants grown in ponds and propagated for restoration efforts in the San Marcos River, Texas. Excess TWR seeds and tillers can be used for experiments on the life history and physiology of this species. In addition, long-term use of outdoor ponds potentially increases the number of refugia TWR plants maintained at San Marcos Aquatic Resources Center (SMARC), providing extra security in the event that an extreme drought or flood results in excessive loss of TWR in the San Marcos River. The results of this project indicate that outdoor ponds can be used to propagate TWR. The use of ponds should also be examined for production of other native aquatic plants needed for long-term restoration efforts in the San Marcos River.