Seed germination studies with Heteropogon contortus

Abstract

Germination characteristics of Heteropogon contortus were investigated in germination cabinets and in the glasshouse using soil trays. Under the former a dual inhibitory system appeared to operate. On the one hand naked caryopses from seeds which were less than 4 months of age were inhibited from germination by a process apparently analogous to epicotyl dormancy. This could readily be broken by applying 1% gibberellic acid and partly broken by repeated wetting and drying. On the other hand between 4 and 12 months, naked caryopses germinated more readily than intact seeds (caryopsis plus glumes, lemmas, etc.). However, the dormancy factor apparently associated with these structures could not be detected when seed was germinated in soil in the glasshouse and it appeared that they are a necessary protection for the caryopsis under field conditions.The optimal temperature for germination was between 30 and 35°C constant. Alternating diurnal temperatures of less than this appeared to cause reduced germination, and no high-temperature stimulation was observed. Germination was not directly promoted by the passage of a normal grass fire.

Effects of Depth and Duration of Burial on Tanglehead (Heteropogon contortus) Seed Viability and Germination in Southern Texas

“…We detected only a weak interaction between year of collection and duration of burial. Tothill (1977) reported high germination of tanglehead seeds stored at room temperature for up to 39 months; our results support this. Two-year old seeds that were buried generally had similar germination responses throughout our 25-mo burial trial as freshly harvested seeds that were buried.…”

“…A complete understanding of the many factors that affect dormancy (e.g., Wester 1995) is beyond the scope of this study. Tothill (1977) identified two tanglehead dormancy mechanisms: (1) endogenous dormancy that can be relieved by gibberellic acid, and (2) exogenous inhibition associated with seed • 9 appendages. Tothill (1977) showed that appendage (glumes, lemma) removal relieved seed dormancy under laboratory conditions; these appendages, however, were essential to maintenance of seed viability in the field.…”

“…Tothill (1977) could not determine that light was required for tanglehead germination, and we have excavated numerous seedlings in the field with seeds, located at ca. 3 cm below the soil surface, still attached to the base of the subcoleoptilar internode; thus, it is unlikely that light is required for tanglehead germination.…”

“…In Trial 2, seeds were harvested from plants at an additional study site (Duval Co., Loamy Sand Ecological Site: R083EY705TX) in November 2012; seeds from 2010 and 2012 Duval Co. collections were buried in February 2013 at 5 locations (separated by at least 500 m) at a study site (Sandy Loam Ecological Site: R083CY463TX) in Brooks Co., TX. Collected seeds were stored in paper envelopes at room temperature (23°C) until burial (Tothill 1977). Seeds were placed in aluminum mesh bags (0.011 mm mesh; 50 seeds per bag) and buried at 3.8 cm or 8.9 cm.…”

Quantifying the spatial and temporal distribution of tanglehead (Heteropogon contortus) on South Texas rangelands

“…This subregion has experienced increasing prevalence of tanglehead since the 1990s (Texas Parks and Wildlife Department 2016a; Wester et al 2017). The prevalence of sandy soils and high temperatures in this area provides excellent conditions conducive for the growth of tanglehead (Tothill 1977).…”