Factors Affecting Germination of Coolatai Grass (Hyparrhenia hirta)

Abstract

Coolatai grass is an invasive, perennial grass from Africa and the Middle East that has infested large areas of northern New South Wales, Australia, and also occurs in other Australian states. An understanding of the seed germination ecology of Coolatai grass can assist in predicting its potential distribution and developing effective management strategies. The effects of various environmental factors on Coolatai grass seed germination were investigated in a series of laboratory experiments. The effect of diurnal alternating temperatures (5–45 C) with a 12-h photoperiod were examined on a thermogradient plate. Seed germination occurred at almost all temperature combinations from 5 to 45 C. At moderate temperatures the speed of seed germination was very high; at 30/20 C more than 80% of seeds were germinated within 12 h. Germination was slightly enhanced by the presence of light, but length of photoperiod did not affect germination. Germination at neutral pH was over 90%, and declined to 65% at acidic (pH 4) and alkaline (pH 10) pH levels. Germination was completely inhibited at an osmotic stress of −0.55 MPa or greater and was reduced by 50% at −0.37 MPa. Greater germination in relatively dry soil conditions compared with native species may contribute to the establishment of this species in the field. Results indicate that Coolatai grass seeds can germinate over a wide range of diurnal temperatures, light regimes, pH levels, and under marginal water stress. These characteristics help explain the successful invasion of Coolatai grass and provide evidence that this species is capable of establishing in many parts of Australia.

Germination ecology of wild onion: a rainfed crop weed

“…Germination of coolatai grass was 92% at pH level of 7.00, however at moderate level of pH (5.00) or (9.00) germination was reduced by around 10%. Germination of coolatai grass was reduced at pH level of 4.00 or 10.00 (Chejara et al, 2008). Similar results to those of Chauhan et al (2006f) were found in Lolium rigidum (rigid ryegrass).…”

“…Soil pH is another important environmental factor affecting seed germination of various weeds. Seeds of some weeds can germinate over a broad pH range (Chachalis et al, 2008;Chejara et al, 2008), while other weeds can germinate well in acidic soil conditions (Fried et al, 2008).…”

Germination Ecology of Catchfly (Silene conoidea) Seeds of Different Colors

“…Germination is the process whereby seeds begin to sprout and grow. This process is affected by such factors as temperature (Widderick et al, 2004), drought (Chejara et al, 2008), salts (Chauhan et al, 2006) and burial depth (Koger et al, 2004). The present paper is concerned with the germination of catchfly (Silene conoidea) seeds.…”

Unassisted invasions: understanding and responding to Australia’s high-impact environmental grass weeds

“…Other ecological novelties have also been identified retrospectively among the high-impact species. These include an ability to perform well under high-light conditions (Robbins 2009), rapid post-rain germination (Keir and Vogler 2006;Vogler and Owen 2008), broad germination requirements that include the ability to germinate in drier soils than native species (Chejara et al 2008) and the ability to rapidly exploit phosphorus through fast-growing root systems (Christie 1975;Christie and Moorby 1975). However, the potential of such ecological novelties to enable species to successfully invade and become dominant without the assistance of anthropogenic disturbance still needs to be properly tested.…”