| 1. |
- Fogelfors, Håkan
(författare)
-
Seasonal restrictions of bud growth on roots of Cirsium arvense and Sonchus arvensis and rhizomes of Elymus repens
- 2010
-
Ingår i: Weed Research. - : Wiley. - 0043-1737 .- 1365-3180. ; 50, s. 102-109
-
Tidskriftsartikel (refereegranskat)abstract
- P>The success of weed management aimed at depleting the regenerative structures of perennial weeds depends largely on the sprouting activity of rhizome and root buds. Seasonal variation in sprouting of these buds on Cirsium arvense, Sonchus arvensis and Elymus repens was studied for plants collected from Denmark, Finland, Norway and Sweden. At 2-week intervals from July to October, 5-cm fragments of roots or rhizomes were cut from plants grown in buckets and planted into soil in pots, half of which were placed immediately into growth chambers at 18 degrees C for 4 weeks. The other half of the pots were initially placed in a dark room at 2 degrees C for 4 weeks before being transferred to the same growth chamber, also for 4 weeks. During the growth chamber period, the numbers of emerged shoots in each pot were counted weekly. The sprouting activity of C. arvense and E. repens was relatively uniform during this period and bud dormancy was not apparent. In all ecotypes of S. arvensis, innate bud dormancy developed during the latter part of the growing season. For all three species, differences in sprouting readiness were found among ecotypes. The results imply that C. arvense and E. repens are more likely to be controlled by mechanical measures in autumn than S. arvensis.
|
|
| 2. |
- Karlsson, Laila, et al.
(författare)
-
Seed dormancy and germination in the summer annual Galeopsis speciosa
- 2006
-
Ingår i: Weed research (Print). - : Institutionen för fysik, kemi och biologi. - 0043-1737 .- 1365-3180. ; 46:5, s. 353-361
-
Tidskriftsartikel (refereegranskat)abstract
- This study examined germination and dormancy in Galeopsis speciosa (Lamiaceae), a common summer annual weed in cold-temperate areas. Seeds collected in southern Sweden were subjected to several experiments. The seeds were dormant at maturity. Seeds sown outdoors after collection produced a small number of seedlings, that emerged early in the spring. After long cold stratification or stratification outdoors over two winters, the maximum germination was 40 to 50%; germination occurring over a wide range of temperatures. Warm stratification preceding cold stratification had no effect on germination, but repeated warm and cold periods seemed to promote germination. Gibberellic acid (GA) stimulated germination but full germination was only achieved after more than two months of incubation at the most suitable temperature regime tested. Excised embryos grew and developed into normal seedlings. With these results, the species does not fit into the currently used system for seed dormancy classifications. The response to GA and the growth of excised embryos indicate non-deep or intermediate physiological dormancy, but dormancy alleviation by stratification was not in line with the guiding principles for these classifications. Galeopsis speciosa has a strong dormancy that is sufficiently alleviated during the winter to allow germination of only part of a seed batch each year, hence a stepwise germination pattern occurs over a period of several years.
|
|
| 3. |
- Karlsson, Laila, et al.
(författare)
-
Comparing after-ripening response and germination requirements of Conyza canadensis and C. bonariensis (Asteraceae) through logistic functions
- 2007
-
Ingår i: Weed research (Print). - : Blackwell. - 0043-1737 .- 1365-3180. ; 47:5, s. 433-441
-
Tidskriftsartikel (refereegranskat)abstract
- Germination requirements and after-ripening effects during one year of dry storage at 15/5 and 25/15°C (day/night) were compared for Conyza bonariensis and C. canadensis (Asteraceae). A logistic function was fitted to the results from tests over time in various incubation conditions, using three populations of each species as replicates. Time required for response to dry storage was measured by using a new method; the third derivative of the logistic function. Therefore, a point when major germination was achieved could be detected, without having to rely on maximum germination (which is uncertain), individual data points or any subjectively chosen limit. Fresh seeds of both species were dependent on light for germination and after-ripening was mainly manifested by increasing germination in darkness. Low dormancy status and light requirement might indicate that soil cultivations should rapidly reduce the seed banks of these species, although fecundity and wind dispersal will affect population levels. The species differed in their germination response, with C. bonariensis germinating at lower temperatures than C. canadensis. This seemingly counter-intuitive result may explain the prevention of fatal germination of C. canadensis in cold conditions and its behaviour as a summer annual in northern climates, while C. bonariensis is restricted to warmer parts of the world.
|
|
| 4. |
|
|
| 5. |
- Anbari, Saghi, et al.
(författare)
-
Sprouting and shoot development of Sonchus arvensis in relation to initial root size
- 2011
-
Ingår i: Weed Research. - : Wiley. - 0043-1737 .- 1365-3180. ; 51, s. 142-150
-
Tidskriftsartikel (refereegranskat)abstract
- To assess the effects of initial root size of Sonchus arvensis on sprouting and shoot development, an outdoor box experiment was performed in Sweden in 2008. Shoot emergence time, shoot numbers, rosette size and flower production were quantified as functions of root length and weight. Emergence of the first shoot per root and of later cohorts was delayed with decreasing root length and weight. Number of shoots per root increased with root length and weight, but per unit root length and weight, short roots produced more shoots. The first emerging rosettes were, for rosettes of a given age, larger for longer roots. Total rosette area per root 5 weeks after planting increased with increasing root length and weight. The number of flowers and production of mature seeds were positively related to root length and weight, because of delayed sprouting of short and light roots. The proportion of flowers leading to mature seeds declined with shoot emergence time. By clarifying relationships between root size and growth parameters, this study showed that fragmenting of S. arvensis roots delays phenological development and hampers reproduction by seeds. The information may be used to refine mechanical weed control strategies for S. arvensis.
|
|
| 6. |
|
|
| 7. |
- Andersson, Lars, et al.
(författare)
-
Seasonal changes in seed dormancy of Solanum nigrum and Solanum physalifolium
- 2009
-
Ingår i: Weed Research. - : Wiley. - 0043-1737 .- 1365-3180. ; 49, s. 90-97
-
Tidskriftsartikel (refereegranskat)abstract
- The seed dormancy cycle in Solanum nigrum and S. physalifolium was studied in relation to seasonal temperature. Seed lots of both species were buried in pots outdoors in a randomized complete block design with four replicates from November 2004 to November 2006. At regular intervals, samples of the seeds were randomly exhumed and tested for germination in incubators at three temperatures and light/darkness regimes. For both species low winter temperature weakened dormancy and high temperature strengthened it. Dormancy induction mainly occurred from August to October in both species after experiencing warm temperatures. An exception from the general pattern of seed dormancy was however observed when seed germination percentages were temporarily reduced in early spring followed by a peak in germination before the main period of strong dormancy in S. nigrum. The same phenomenon was observed in S. physalifolium during June in the first year. This short-lived dormancy induction might explain the late emergence of the species. Seed dormancy enables the species to maximize its chance of survival by regulating germination timing to favourable conditions. Therefore, information on the dormancy cycle can be used to predict seedling emergence and optimize weed control operations
|
|
| 8. |
- Andersson, Lars, et al.
(författare)
-
Variation in seed dormancy and light sensitivity in Alopecurus myosuroides and Apera spica-venti
- 2009
-
Ingår i: Weed Research. - : Wiley. - 0043-1737 .- 1365-3180. ; 49, s. 261-270
-
Tidskriftsartikel (refereegranskat)abstract
- Variation in seed dormancy and light sensitivity was studied in Alopecurus myosuroides and Apera spica-venti. Seeds were collected from different populations, at different dates and from plants emerging in autumn or spring, and used in four experiments. In the first experiment, initial dormancy was investigated in light and darkness. In Expt 2, buried seeds were exhumed on 16 occasions, from September 1997 to March 2000, and germinated in light, in darkness and after a 5-s light exposure. In Expt 3, emergence was recorded for seeds sown in pots outdoors. In Expt 4, stratified seeds of A. myosuroides only were exposed to photon irradiance ranging from 0.1 to 25 600 mu mol m(-2). Variation was high among seed collections, but both species showed winter annual dormancy patterns. Apera spica-venti germinated to high percentages in autumn but negligibly in spring. Alopecurus myosuroides germinated less in spring when tested in darkness and after a short light exposure and emerged poorly in spring, which reflected photo-desensitisation during cold stratification. We conclude that the peak of emergence in A. myosuroides, and to some extent in A. spica-venti, is largely regulated by exposure to light interacting with low-level dormancy. This offers valuable information regarding optimal timing of weed control measures.
|
|
| 9. |
|
|
| 10. |
|
|
