Technical Reports Document Library

The purpose of this study was to identify factors that influence sexual and asexual reproduction of Texas Wild-rice (Zizania texana). Data collected during the study were used to examine the characteristics of pollen viability and dispersal, stigma viability, ability to self-pollinate, seed production and quality, minimum distances for successful pollination within and among stands, and asexual output. New information regarding pollination success and seed production for Texas Wild-rice was documented. The study was completed in June 2004 by the U.S. Fish and Wildlife – San Marcos National Fish Hatchery and Technology Center and the Lady Bird Johnson Wildflower Center.

[Excerpted from the Executive Summary]
… The three-year study was designed to identify factors that influence sexual and asexual reproduction in Texas wild-rice (Zizania texana). Four manipulative studies, a field survey, and a compilation of existing seed harvest data (1999 – 2003) were used to examine the characteristics of pollen viability and dispersal, stigma viability and receptivity, ability to self-pollinate, seed production and quality, minimum distances for successful pollination within and among stands, and asexual output….

The combined information in the chapters of this report creates a description of the reproductive biology of Z. texana. Pollen is released during the relatively cool morning hours (between 0200 and 0400) and is short lived (
It can be inferred that successful pollination would occur in large stands with less than 1 m gaps between stands. Gaps greater than 1 m would limit gene flow between stands. Based on the field survey, few individual Z. texana plants grow in isolation and most plants have other Z. texana as neighbors. This is to be expected in a clonal, wind pollinated species. Results from Chapters 2 and 5, together with TPWD’s monitoring of the wild population, suggest that a critical impediment to sexual reproduction occurs at the pollination stage. Fragmentation of stands, gaps between stands, and damaged culms all contribute to failure at the pollination stage. The notable exception to reproductive failure occurs in Sewell Park, where seeds were produced from 1998 to 2004, where the stands are larger and the gaps between stands are smaller relative to the rest of the population.