Influence of Moisture Deficits on the Reproductive Ability of Downy Brome (Bromus tectorum)

Abstract

Downy brome seed production was measured in the field following the establishment of different moisture levels using a line source sprinkler irrigation system. Results indicated that seed production was strongly affected by different moisture levels, with a curvilinear decrease in seed number from higher to lower moisture. In a hydroponic study with water deficits induced by PEG-8000, no seeds were produced when plants were severely stressed (-1.1 MPa) for a 7-day period during culm elongation or anthesis. Number of seeds/panicle was reduced under severe water stress during seed fill, under moderate stress (-0.5 MPa) during anthesis or seed fill, and under mild stress (-0.1 MPa) during anthesis. Water stress also reduced apparent photosynthesis and increased diffusive resistance of flag leaves, particularly under severe stress. In general, water deficits did not affect seed weights or germination percentages in either study.

Overlapping resource use in three Great Basin species: implications for community invasibility and vegetation dynamics

“…However, early season water depletion by Elymus may impact associated Bromus where the two grasses occur in mixed stands. Bromus leaf growth primarily occurs in the spring, and the annual has usually completely senesced by late May (Harris 1967), thus early spring moisture availability is critical for both growth and seed production (Richardson et al . 1989).…”

Defoliation Effects On Bromus Tectorum Seed Production: Implications For Grazing

“…Variation in annual soil moisture and other environmental conditions are other possible factors that need to be considered. A year with greater moisture availability may improve the ability of plants to recover following defoliation-particularly if it should occur in the spring (Harris 1967;Richardson et al 1989)-and may retard phenological development and thus lengthen the growing season. This may require a longer or an additional period of grazing depending partly on when additional precipitation occurs.…”

Consequences of Rainfall Manipulations for Invasive Annual Grasses Vary Across Grazed Northern Mixed-Grass Prairie Sites

“…2) We hypothesized that during precipitation reduction years, the biomass and percent cover of invasive annual bromes would decrease across precipitation reduction treatments due to the added stress of water loss ( Richardson et al 1989 ). Likewise, we predicted that precipitation reduction would cause annual bromes to senesce earlier in the season, with average percent green the lowest under the severest water reduction levels ( Rice et al 1992 ).…”