Light has minimal impact on germination over the 12-month period after dispersal.
•
Seeds can germinate over an extended period (spring through autumn) in the field.
•
The research would aid in understanding I. purpurea seed bank dynamics.
Abstract Field and laboratory experiments were conducted in SC, USA, in 2004/2005 and 2006/2007 to determine the effect of temperature, light, and spring burial onIpomoea purpurea(L.) Roth. seed germination over a 12-month period after seed maturation in the field. The seed collections used for the temperature and light studies had physical dormancy (water-impermeable), with 10–23% and 17–46% germination, respectively, of the freshly matured viable seeds. Freshly matured seeds used for the temperature study germinated to higher percentages at 15–25 °C constant. During winter (3 months after seed maturation), seed germination was higher at 30 °C constant or 22.5/37.5 °C fluctuating. During spring (6 months after seed maturation), there was a widening of thermal range (10–40 °C constant or 2.5/17.5 to 27.5/42.5 °C fluctuating) for germination. Germination of surface-lying or buried seeds was higher at 35–40 °C constant or 22.5/37.5–27.5/42.5 °C fluctuating in late summer (9 months after maturation) and autumn (12 months after maturation). Light had minimal influence on germination of surface or buried seeds of the tested population over the 12-month after-ripening period. A temperature-mediated annual dormancy continuum ofI. purpureaseed has been proposed in this research, which will contribute to the development of weed emergence models aimed at improving strategies forI. purpureacontrol in the field. Keywords
Published Date
South African Journal of Botany March 2015, Vol.97:1–8,doi:10.1016/j.sajb.2014.11.003
Author
G.J. Brits a,,
N.A.C. Brown b,
F.J. Calitz c,
J. Van Staden d,
aHorticultural Division, Institute for Fruit Research, Agricultural Research Council, P.O. Box 5026, Stellenbosch 7599, South Africa
bConservation Biology Research Unit, National Botanical Institute, Kirstenbosch, P/Bag X7, Claremont 7735, South Africa
cBiometry Services, Agricultural Research Council, P.O. Box 8783, Pretoria 0001, South Africa
dResearch Centre for Plant Growth and Development, School of Biological and Conservation Sciences, University of Kwazulu-Natal Pietermaritzburg, Private Bag X01, Scottsville 3209, South Africa
Received 20 July 2014. Revised 10 November 2014. Accepted 12 November 2014. Available online 29 December 2014. Edited by MI Daws
Highlights
•
Leucospermum seed storage was investigated, including 4 years of soil-storage in fynbos.
•
Dry, open shelf-stored seeds declined quickly (2–4 years) whereas soil-stored seeds remained viable.
•
Seeds sown under simulated fynbos conditions spread (strategically extended) germination over 5 years.
•
Combined results indicate extended germination in fynbos for the freshly dispersed seed cohort.
•
Testa-scarified old-cohort seeds are implicated to germinate early, evenly, en masse.
•
Long term wet–dry cycling due to rainfall may regulate cellular repair and longevity.
Abstract Seed longevity, the control of dormancy and the eventual fate of seeds were studied in two experiments simulating conditions in natural fynbos. In one experiment a batch of mature, freshly harvested, intact achenes (“seeds”) of the myrmecochorous speciesLeucospermum cordifoliumwas divided into lots, of which one was buried in mesic mountain fynbos (experiencing a mediterranean-type climate with hot summers). Other seed lots were stored open at room temperature and in closed nitrogen filled containers at 3 °C, respectively. Stored seeds were sampled and germinated under optimal laboratory (viability estimate) and seed bed (vigour estimate in fynbos) conditions, during autumn, after 0 (control), 1, 2 and 4 years. Low temperature stored seeds maintained a high viability and vigour for c. two years but ambient temperature storage led to a marked decline after 1 year ending in almost complete mortality after 4 years of shelf storage. Four year soil-stored seeds, by contrast, maintained a high viability and vigour, of 80% and 60% respectively of the original seed source values. The soft pericarp/elaiosome in soil-stored seeds disappeared completely whilst the testa became progressively scarified over time. The strongly increased germination rate (velocity) in soil-stored seeds was attributed to natural oxygenation mediated by testa scarification. In another experiment freshly matured intact achenes were oxygenated with 1% H2O2and the pericarps removed. Disinfection and benzyladenine growth regulator soaking (200 mg L− 1for 24 h) were applied as separate treatments. The seeds were then sown at 1 cm depth in a standard seed bed in autumn and germination was recorded in the first winter season and, in the undisturbed seed bed, in each subsequent winter for 5 germination seasons. H2O2oxygenated seeds gave a much higher germination percentage and rate than non-oxygenated seeds, although sporadic germination continued over five germination seasons in all treatments. Seeds germinated only during autumn and early winter each year. The results of the combined experiments suggest that, in nature,Leucospermumseeds can persist underground for long periods. We propose a model of soil-stored seeds in which the intact testa of freshly dispersed seeds is gradually scarified, leading to uneven, extended germination of the young (mainly current season) seed cohort over the first (and possibly several) post-fire germination seasons; and the synchronous germination of the older (scarified), larger, portion of the seed bank, leading to massive species recruitment during the early stages of the first post-fire winter germination season. The numerous wet–dry cycles due to natural rainfall, over prolonged periods in fynbos, may contribute to seed longevity via cellular repair processes. Keywords
Published Date
Crop Protection June 2015, Vol.72:57–65, doi:10.1016/j.cropro.2015.03.004 Review Author
Khawar Jabran a,,
Gulshan Mahajan b
Virender Sardana b
Bhagirath S. Chauhan c,,
aDepartment of Plant Protection, Adnan Menderes University, Aydin, Turkey
bPunjab Agricultural University, Ludhiana, Punjab, India
cQueensland Alliance for Agriculture and Food Innovation (QAAFI), The University of Queensland, Toowoomba, Queensland, Australia
Received 1 November 2014. Revised 2 March 2015. Accepted 3 March 2015. Available online 13 March 2015.
Highlights
•
Crop yield losses by weeds surpass 30%.
•
Diversity in weed control practices reduces the herbicide resistance evolution in weeds and avoids environmental pollution.
•
Microorganisms facilitate the process of allelopathy in the soil environment.
•
Use of allelopathy can play an important role in achieving sustainable and integrated weed control.
•
Sowing of allelopathic cultivars can help to reduce weed pressure without an extra cost.
Abstract Weeds are a hidden foe for crop plants, interfering with their functions and suppressing their growth and development. Yield losses of ∼34% are caused by weeds among the major crops, which are grown worldwide. These yield losses are higher than the losses caused by other pests in the crops. Sustainable weed management is needed in the wake of a huge decline in crop outputs due to weed pressure. A diversity in weed management tools ensures sustainable weed control and reduces chances of herbicide resistance development in weeds. Allelopathy as a tool, can be importantly used to combat the challenges of environmental pollution and herbicide resistance development. This review article provides a recent update regarding the practical application of allelopathy for weed control in agricultural systems. Several studies elaborate on the significance of allelopathy for weed management. Rye, sorghum, rice, sunflower, rape seed, and wheat have been documented as important allelopathic crops. These crops express their allelopathic potential by releasing allelochemicals which not only suppress weeds, but also promote underground microbial activities. Crop cultivars with allelopathic potentials can be grown to suppress weeds under field conditions. Further, several types of allelopathic plants can be intercropped with other crops to smother weeds. The use of allelopathic cover crops and mulches can reduce weed pressure in field crops. Rotating a routine crop with an allelopathic crop for one season is another method of allelopathic weed control. Importantly, plant breeding can be explored to improve the allelopathic potential of crop cultivars. In conclusion, allelopathy can be utilized for suppressing weeds in field crops. Allelopathy has a pertinent significance for ecological, sustainable, and integrated weed management systems. Keywords
