Environmental factors affecting the germination and emergence of white horehound (Marrubium vulgare L.) : A weed of arid-zone areas
- Authors: Javaid, Muhammad , Florentine, Singarayer , Ali, Hafiz , Chauhan, Bhagirath
- Date: 2018
- Type: Text , Journal article
- Relation: Rangeland Journal Vol. 40, no. 1 (2018), p. 47-54
- Full Text: false
- Reviewed:
- Description: White horehound (Marrubium vulgare L.), is a troublesome weed of arid zones, particularly in cropping and grazing areas. Understanding the seed ecology of white horehound is relevant to its management. The present study investigated the effects of temperature, light, osmotic potential, salinity, pH, and seeding depth on seed germination and seedling emergence of white horehound. Seeds germinated over a wide range of temperatures, with highest germination (100%) occurring at 25/20°C in either 12-h alternating light/dark or complete darkness. Germination decreased from 92% to 10% as the osmotic potential decreased from 0 to minus 0.6MPa and germination was completely inhibited at minus 0.8MPa. Increasing concentration of sodium chloride (salinity) from 50 to 150mM reduced germination from 68% to 11% but was completely inhibited at 200mM. Germination was not limited by variation of pH in solutions of pH 5 to pH 10. Maximum germination (99%) occurred at pH 7, but slightly decreased (90%) in acidic or alkaline media. Surface located seeds were highly germinable (87%) where seedling emergence significantly declined as seeding depth increased from 0.5 to 3cm. Nil seedling emergence was occurred at 4cm burial depth. Light significantly affected germination, time to 50% germination, mean germination time and germination index. Increasing osmotic and salinity stress both significantly increased the time to start germination, time to 50% germination, mean germination time, but decreased germination index. Burial depth adversely affected seedling emergence with surface located seedlings emerging earlier (4.2 days) compared with 20 days for seeds buried at 3cm. Results suggest that effective management of white horehound should consider targeting surface located seeds in combination with tools that induce minimal soil disturbance, particularly in relatively non-saline environments.
Influence of selected environmental factors on seed germination and seedling survival of the arid zone invasive species tobacco bush (Nicotiana glauca R. Graham)
- Authors: Florentine, Singarayer , Weller, Sandra , Graz, Patrick , Westbrooke, Martin , Florentine, Arunthathy , Javaid, Muhammad , Fernando, Nimesha , Chauhan, Bhagirath , Dowling, Kim
- Date: 2016
- Type: Text , Journal article
- Relation: Rangeland Journal Vol. 38, no. 4 (2016), p. 417-425
- Full Text: false
- Reviewed:
- Description: Tobacco bush (Nicotiana glauca R. Graham) is an aggressive invading species, which is active after disturbances such as high rainfall events and flooding. Past studies have focussed on population dynamics and allelopathic effects associated with the species, but little is known about its seed ecology. To address this dearth of information, this study aimed to investigate: (i) the effect of various stress factors (temperature, light, osmotic potential, salt stress, heat-shock, a combination of heat-shock and smoke, pH buffer, and burial depth of seed) on seed germination and seedling emergence, and (ii) factors affecting the fate of seedlings. The results show that N. glauca was able to germinate over a broad range of temperatures with highest seed germination occurring at 30/20°C with 12h of light and 12h of dark conditions. Seed germination was greatest (89%) when seeds were placed on the soil surface and emergence decreased considerably as planting depth increased from 0.5 to 1.5cm. Water stress greatly reduced seed germination (58% germination at osmotic potentials below -0.2 MPa) and germination was completely inhibited at water potentials of -0.4 to -0.6 MPa. Although increasing salinity reduced the seed germination of this invasive species, N. glauca seed was able to germinate in both alkaline (81% at pH 10) and acidic (80% at pH 4) conditions. The trial on the effect of seed age and field seed burial on seed germination showed a slight decline in seed germination after 120 days of burial compared with non-buried seeds. Further, the combined effect of heat-shock and smoke effectively inhibited the germination of N. glauca seeds; however, our study shows that seedlings of N. glauca can withstand heat-shock of up to 130°C. Studies such as this will assist in the development of control strategies to prevent the spread of this invasive species into arid landscapes. © 2016 Australian Rangeland Society.