Invasive Cheatgrass (Bromus tectorum)

Reproductive Strategies


 Cheatgrass is an annual, cool season grass which is known to be discreet because of its small size (Speziale et al. 2013). For a more in depth description, check out the interactions page.  It is an annual grass whose effects on the environment can be clearly viewed from year to year because of its dominant characteristics. The grass germinates in autumn, grows slowly, and by the end of December is generally two to four centimeters tall. During winter, the seedlings enter a semi-dormant state in order to survive. By spring time, Cheatgrass resumes its lifecycle growing to heights of around fifty to sixty centimeters. Cheatgrass is a flowering plant which does so in the summer ( Zouhar 2003).  Bromus tectorum demonstrates a germination pattern that is indicative of wintertime annuals (Bykova and Sage 2012) . During dispersion, the seeds are dormant, to some degree. These seeds will start to grow when the conditions are right. If the conditions are not favorable, the seed will become dormant again until spring (Forbis 2010). The seeds of Bromus tectorum have the potential to remain viable for up to five years (USDA 2005; CalIPC 2014).  This means that even older seeds can grow after a period of time has passed.


Seed Production and Dispersal       

Bromus tectorum reproduces by seed only (Forbis 2010). The species is mostly autogamous which means it reproduces through self- fertilization or pollination. These autogamous organisms for the most part go through cleistogamy. Cleistogamy is defined as the process of a flowering plant self- fertilizing without the flower opening (Zouhar 2003). In other words, the fertilization happens internally. Even though Cheatgrass is primarily a self-fertilizing organism, it also can take part in cross fertilization. The type of breeding system is environment dependent, allowing Bromus tectorum to adapt to the surroundings. (Zouhar 2003) The seeds of the plant are typically dispersed by the wind, but this is not always the case. The seed coat of cheatgrass plants are covered in bristle like structures. This allows for the seed coat to attach to the feathers or fur of animals maximizing dispersal of the seeds. Also, it has the capacity to produce up to three hundred seeds per plant (CalIPC 2014).  Having a large seedbank is a reproductive strategy that helps maintain population size. The seed are very durable and can withstand high soil temperatures. Because of this, along with Bromus tectorum’s ability to remain dormant for long periods of time, it is believed that there are twice as many seeds available as there are growing as established plants. (CalIPC 2014)  Even in drought conditions, Bromus tectorum can produce enough seeds to at least propagate itself for the next growing season. Once the seeds have been spread through wind or animals, shoot growth can occur. The young plant extents from its shoot apical meristem and the organs of a plant begin to form (roots, stem, and leaves). This typically happens in early spring and continues until most of the natural resources are exploited from the area. (CalIPC 2014)


Influence of Roots

Cheatgrass is a dominant and effective invasive species because the grass uses more water than the other plants early in the growing season. This allows for Bromus tectorum to have greater root and shoot growth rate because it initiates growth at lower temperatures in comparison to other species. (Parkinson et al. 2013)   Cheatgrass produces roots around twenty centimeters long and then propels lateral roots out far distances within the soil. These lateral roots are how the plant is able to thrive so well. (CalIPC 2014) Cheatgrass also becomes denser in areas from year to year.  An area of ten plants per meter squared can increase to around ten thousand plans per meter squared within three years. (Parkinson  et al. 2013) This act limits the establishment of other species in the environment. For more information about the root system in Cheatgrass, take a look at the adaptation page.


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