Regeneration Potential of Distaff Thistle in Central Texas

Abstract

Seed production and seed reserves in the soil were determined for distaff thistle (Carthamus lanatus) at two grazed range sites in central Texas. Seed production ranged from 345 to 376 seeds/ft sq. Seed bank density ranged from 16 to 23 seeds/ft sq, with 84% or more of the seed occurring in the top 1 inch of soil. Greater than 58% of the seeds extracted from soil samples were viable as determined by a tetrazolium test. Persistent testa halves (seed coat segments), remaining in the soil after germination, ranged from 37 to 72/ft sq, with 91% or more occurring in the top 1 inch of soil. Seeds were harvested from one site and exposed to different light/dark and dark/light regimes over a 14-day period to determine light requirements forgermination. Seeds exposed to at least 12 h of light per day during initial imbibition had mean germlnarlon times of about 3.4 days and greater than 80% cumulative germination. Light enhanced the germination responses of seeds kept in darkness during the first 7 days of the 14-day period. A small portion (10%) of non-dormant seeds germinated in total darkness.