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- Andersson, Lars, et al.
(författare)
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Sprouting capacity from intact root systems of Cirsium arvense and Sonchus arvensis decrease in autumn
- 2013
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Ingår i: Weed research (Print). - : Wiley. - 0043-1737 .- 1365-3180. ; 53:3, s. 183-191
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Tidskriftsartikel (refereegranskat)abstract
- Perennial weeds are often controlled by mechanical means, which aim at stimulating axillary and adventitious buds to sprout. This happens when the apical dominance of the main shoot is removed by defoliation or when the underground system is fragmented. By repeating the measures, the result is a depletion of storage compounds, which weakens the plants and reduces their capacity to grow and reproduce. However, timing is critical. Earlier research has indicated that emergence from fragments of Sonchus arvensis cease during a period in autumn, while the seasonal pattern of sprouting in Cirsium arvense appears to be inconsistent. We studied the emergence pattern of defoliated plants with undisturbed root systems, from late summer to early spring. Potted plants grown outdoors were exhumed at regular intervals, put under forcing conditions for 4weeks, after which shoots above and below soil level were counted and weighed together with the remaining root systems. In both species, the number and weight of emerged shoots decreased during a period in the autumn. In C.arvense, underground shoots were constantly produced during the same period, while fewer underground shoots were present in S.arvensis. For the latter species, apical dominance does not fully explain the effect; thus, endodormancy might be involved. Root weight increased until withering and did not explain the lack of emergence. Our results suggest an impaired sprouting capacity of undisturbed root systems of C.arvense and S.arvensis during SeptemberOctober, which has implications for the timing and method of control of these species.
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- Boström, Ullalena, et al.
(författare)
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Seasonal variation in sprouting capacity from intact rhizome systems of three perennial weeds.
- 2013
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Ingår i: Weed research (Print). - : Wiley. - 0043-1737 .- 1365-3180. ; 53:5, s. 387-398
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Tidskriftsartikel (refereegranskat)abstract
- The three rhizomatous perennials Elytrigia repens, Equisetum arvense and Tussilago farfara are all problematic in Scandinavian agriculture, due to their low susceptibility to soil cultivation. While repeated soil tillage is a fundamental part of the integrated control of these species, it is highly energy consuming and inefficient during periods when little sprout regrowth occurs. Substituting cultivation with mowing will reduce the environmental impact and labour costs, but its efficiency will still depend on the capacity of plants to sprout. Therefore, we studied the seasonal pattern in emergence and rhizome biomass allocation from July to April in six populations for each of the species. Plants were grown outdoors in pots buried in soil and exhumed at regular intervals in a two-year experiment. In all three species, biomass allocation to rhizomes continued until late in the autumn. Emergence was severely impaired in E.arvense and T.farfara in September-October, while in E.repens, there was no such reduction in the number of emerged shoots. However, in the latter species, the shoot/rhizome ratio decreased and remained low until the plants had been exposed to a period of low temperatures. The increase in shoot/rhizome ratio for E.repens coincided with the resumed capacity to emerge for E.arvense and T.farfara. These results imply that there is no need to repeat a defoliation of E.arvense and T.farfara, if carried out in September-October. However, removal of the aerial plant parts early in the autumn is important to interrupt the upload of storage compounds to the rhizome systems of all species.
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- Liew, Josefine, et al.
(författare)
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A guide to generalized additive models in crop science using SAS and R
- 2015
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Ingår i: Communications In Biometry And Crop Science. - 1896-0782. ; 10, s. 41-57
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Tidskriftsartikel (refereegranskat)abstract
- Linear models and generalized linear models are well known and are used extensively in crop science. Generalized additive models (GAMs) are less well known. GAMs extend generalized linear models through inclusion of smoothing functions of explanatory variables, e.g., spline functions, allowing the curves to bend to better describe the observed data. This article provides an introduction to GAMs in the context of crop science experiments. This is exemplified using a dataset consisting of four populations of perennial sow-thistle ( Sonchus arvensis L.), originating from two regions, for which emergence of shoots over time was compared.
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| 9. |
- Liew, Josefine
(författare)
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Dormancy in reproductive vegetative buds in creeping perennials dominating the agricultural weed flora in Scandinavia
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Dormancy, which is the inability to initiate normal growth under otherwise favourable conditions, is an adaptation to escape sprouting prior to seasonal cold temperatures and/or drought in areas where winters are harsh or summers dry. Dormancy in woody perennials of northern temperate areas is, in general, induced by photoperiodic and/or temperature changes, and released after prolonged exposure to chilling. Besides being species specific, northern ecotypes are usually more sensitive to inductive signals than are southern ecotypes (in cold temperate areas). Dormancy in perennial weeds has been little studied, but might influence the effect of weed control measures. These often involve repeated fragmentation of the roots or rhizomes to stimulate re-sprouting, thus reducing the storage of nutrient reserves. Such measures would be a waste of energy and time if conducted during a period of dormancy. Furthermore, herbicide applications might be less efficient, since there is no or little transport to reproductive organs. In this thesis, the autumnal growth pattern of five perennial weeds, which all propagate vegetatively from underground adventitious or axillary buds, has been studied. In an outdoor pot experiment, emergence from defoliated plants with undisturbed underground systems was followed at two weeks intervals from late July to late January/April, for 2 years. During the second year, sprouting capacity from root and rhizome fragments was also tested. Emergence was impaired in Cirsium arvense, Equisetum arvense, Sonchus arvensis and Tussilago farfara during a period in September-October. This seasonality was, however, not preserved in C. arvense root buds after fragmentation of the root system. Fragmented rhizomes of Elytrigia repens, originating from southern Sweden, sprouted less readily in September-October. The shoot-to-rhizome ratio of this species was lowest during the same period. A climate chamber experiment suggested a photoperiodic control of sprouting from fragments of S. arvensis, with least sprouting in short photoperiods (12 h of light) combined with high temperature. None of the 12 combinations of photoperiods and temperatures used induced dormancy in C. arvense. In neither of the experiments could timing of dormancy onset be attributed to the latitudinal origin of the plants.
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| 10. |
- Liew, Josefine, et al.
(författare)
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Influence of temperature and photoperiod on sprouting capacity of Cirsium arvense and Sonchus arvensis root buds
- 2012
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Ingår i: Weed research (Print). - : Wiley. - 0043-1737 .- 1365-3180. ; 52:5, s. 449-457
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Tidskriftsartikel (refereegranskat)abstract
- Influence of temperature and photoperiod on sprouting capacity of Cirsium arvense and Sonchus arvensis root buds. Weed Research.52, 449-457. Summary Timing of treatment is a key to successful and sustainable weed management. For perennial weeds, highly energy-demanding, repeated stubble cultivation or tillage is a common strategy in organic agriculture. The fragmentation of underground material stimulates root buds to grow and, if repeated, significantly reduces the energy and nutrient resources of the roots. However, the effect might differ depending on variation in sprouting over the season and among species. Here, we studied the impact of different photoperiods and temperatures on sprouting capacity of root buds of Cirsium arvense and Sonchus arvensis in a climate chamber experiment. Two populations of each species, collected in northern and southern Sweden, were used. Plants were exposed to long (18 h), short (12 h) or decreasing (from 18 to 8 h) photoperiods in combinations with high (18/12 degrees C for 16/8 h), low (12/6 degrees C), decreasing (from 21 to 5 degrees C in 4 weeks) or constant high (16 degrees C) temperatures. Sprouting capacity was evaluated based on the proportion of sprouting buds from short root fragments. Neither temperature nor photoperiod affected root bud sprouting in C. arvense, while in S. arvensis, photoperiod seemed to regulate sprouting capacity. The proportion of sprouted buds decreased in short photoperiods, especially if combined with high temperature. In northern conditions, this suggests that weeding strategies based on fragmentation of the root system of S. arvensis will have low efficiency if the autumns are warm.
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