PRIMARY SEED DORMANCY IN DIFFUSE AND SPOTTED KNAPWEED

1988 ◽  
Vol 68 (3) ◽  
pp. 775-783 ◽  
Author(s):  
DARYL G. NOLAN ◽  
MAHESH K. UPADHYAYA
Keyword(s):  
Gibberellic Acid ◽  
Seed Dormancy ◽  
Red Light ◽  
Centaurea Maculosa ◽  
Spotted Knapweed ◽  
Centaurea Diffusa ◽  
Primary Dormancy ◽  
Pigment System ◽  
Large Numbers ◽  
Subsequent Exposure

Large numbers of viable, diffuse (Centaurea diffusa Lam.) and spotted knapweed (C. maculosa Lam.) seeds (achenes), collected in the interior of British Columbia, failed to germinate in darkness at 25 °C. This primary dormancy was released to varying degrees by gibberellic acid, exposure to red light, or excision of the distal end of the seed. The effect of red light was negated by subsequent exposure to far-red light. The demonstration of red/far-red reversibility implicates the phytochrome pigment system in the light-sensitive germination of knapweed seeds. Seeds collected from different sites, and from individual plants within sites, had different germination levels in darkness and following exposure to 2 min of red light. Three types of germination behavior were evident: nondormant seeds germinated in darkness; light-sensitive dormant seeds germinated in response to red light; and light-insensitive dormant seeds failed to germinate after 5 d of continuous red light. Seeds of all three germination types were found on individual plants.Key words: Centaurea diffusa, Centaurea maculosa, knapweed, seed dormancy, light-sensitive germination, germination polymorphism

Induction of bolting by gibberellic acid in rosettes of diffuse (Centaurea diffusa) and spotted (C. maculosa) knapweed

1986 ◽  
Vol 64 (11) ◽  
pp. 2428-2432
Author(s):  
Mahesh K. Upadhyaya
Keyword(s):  
Gibberellic Acid ◽  
Stem Growth ◽  
Field Conditions ◽  
Spotted Knapweed ◽  
Centaurea Diffusa ◽  
Diffuse Knapweed

An attempt was made to induce synchronous bolting of knapweed (Centaurea spp.) rosettes with gibberellic acid (GA3) under greenhouse conditions. Single or double (2 weeks apart) sprays of GA3 (0, 0.3 × 10−4, and 1.5 × 10−4 M) were applied to 10- to 115-day-old diffuse knapweed (C. diffusa Lam.) rosettes. With the exception of 10- and 25-day-old rosettes, highly synchronous bolting was induced by double applications of 1.5 × 10−4 M GA3. Bolted plants flowered within 8 to 10 weeks of treatment but did not form seeds because of the absence of pollinators in the greenhouse. The size of bolted plants and the percentage of plants bearing flowers depended on rosette age at the time of GA3 application. With a single GA3 application or with two applications at lower concentration, uneven and (or) irregular bolting occurred. Occasionally, the initial rapid stem growth induced by GA3 was arrested, resulting in the formation of aerial rosettes. GA3 also induced bolting in spotted knapweed (C. maculosa Lam.). Induction of synchronous bolting may be useful in mechanical, biological, and (or) environmental (e.g., winter-killing) control of biennial weeds. Its feasibility under field conditions, however, remains to be demonstrated.

Distribution of Urophora affinis and U. quadrifasciata, Two Flies Introduced for Biological Control of Spotted Knapweed (Centaurea maculosa) in Montana

Weed Science ◽  
1987 ◽  
Vol 35 (2) ◽  
pp. 145-148 ◽  
Author(s):  
Jim M. Story ◽  
Robert M. Nowierski ◽  
Keith W. Boggs
Keyword(s):  
United States ◽  
Biological Control ◽  
North America ◽  
Positive Relationship ◽  
The United States ◽  
Centaurea Maculosa ◽  
Spotted Knapweed ◽  
Seed Head ◽  
Strong Positive Relationship ◽  
Southeasterly Direction

A survey was conducted at 88 sites in Montana in 1984 and 1985 to determine the distribution of Urophora affinis Frauenfeld and U. quadrifasciata (Meigen), two seed head flies released on spotted knapweed (Centaurea maculosa Lam. # CENMA) in North America. U. affinis, released in Montana during 1973 to 1977, was found at 40 of the 88 sites. The fly was concentrated within a short radius (about 5 to 8 km) of release sites, even at sites having well-established populations. U. quadrifasciata, released in British Columbia in 1972, but not in the United States, was found at 84 sites. The data suggest that the fly entered the state in the northwest corner and dispersed in a southeasterly direction. There was a strong positive relationship between mean number of galls per seed head and percent infestation for both fly species.

Contrasting seed germination responses to red and far-red light in Leptospermum scoparium and Melicytus ramiflorus

2000 ◽  
Vol 27 (11) ◽  
pp. 1069
Author(s):  
Helen Herron ◽  
John Clemens ◽  
Dennis H. Greer
Keyword(s):  
Seed Germination ◽  
Red Light ◽  
Green Light ◽  
Photon Flux ◽  
Short Term ◽  
Short Term Exposure ◽  
Subsequent Exposure ◽  
R:Fr Ratio ◽  
Leptospermum Scoparium

Effects of red light (R) and far-red light (FR), and selected photon flux densities (PFD) of photosynthetically active radiation (PAR) on seed germination in the photoblastic, primary colonising species Leptospermum scoparium J. R. et G. Forst. and the late secondary successional Melicytus ramiflorus J. R. et G. Forst. were studied. A continuous R dose response curve forL. scoparium germination was developed, unifying data from experiments using long-term exposure to PAR with those following short-term exposure to R. The threshold R dose needed to effect germination was ~0.1 mmol m –2 , and the response was saturated at 1000 mmol m –2 . Stimulation of germination by R was reversed by a subsequent exposure to FR. These features are consistent with a low-fluence response mediated by phytochrome B. FR reversal of germination was achieved at a dose two orders of magnitude lower than that of R required to induce initial germination. However, when both R and FR were provided simultaneously, the FR dose needed to even partially inhibit germination (34% compared to > 95% in controls) was two orders of magnitude higher than the R dose (R:FR ratio = 0.007). Germination in L. scoparium was also stimulated in up to 12% of seed upon diurnal exposure to FR, or by green light (~2 mol m –2 ), indicating a very-low-fluence response mediated by phytochrome A also operating in this species. In contrast, seed germination in M. ramiflorus was relatively unresponsive to R, and secondary dormancy was induced by high PFD (515 mol m –2 s –1 ).

scholarly journals Rice GERMIN-LIKE PROTEIN 2-1 Functions in Seed Dormancy under the Control of Abscisic Acid and Gibberellic Acid Signaling Pathways

2020 ◽  
Vol 183 (3) ◽  
pp. 1157-1170 ◽  
Author(s):  
Haiting Wang ◽  
Yuman Zhang ◽  
Na Xiao ◽  
Ge Zhang ◽  
Fang Wang ◽  
...  
Keyword(s):  
Abscisic Acid ◽  
Gibberellic Acid ◽  
Signaling Pathways ◽  
Seed Dormancy ◽  
Gibberellic Acid Signaling

Cnicin concentrations in Centaurea maculosa, spotted knapweed

1987 ◽  
Vol 15 (3) ◽  
pp. 313-320 ◽  
Author(s):  
Laura J. Locken ◽  
Rick G. Kelsey
Keyword(s):  
Centaurea Maculosa ◽  
Spotted Knapweed

Genetic adaptation for seed dormancy in Avena fatua

1976 ◽  
Vol 54 (3-4) ◽  
pp. 306-312 ◽  
Author(s):  
J. M. Naylor ◽  
S. Jana
Keyword(s):  
Genetic Variability ◽  
Seed Dormancy ◽  
Natural Populations ◽  
Avena Fatua ◽  
Genetic Adaptation ◽  
Agronomic Practices ◽  
Primary Dormancy ◽  
Local Populations ◽  
Wild Oats

Genetic variability affecting duration of primary dormancy is demonstrated in natural populations of wild oats. Marked differences were found among local populations in germination behavior. The evidence suggests that these differences result in part from genetic adaptation to agronomic practices.

METZNERIA PAUCIPUNCTELLA ZELLER (LEPIDOPTERA: GELECHIIDAE), A MOTH INTRODUCED AGAINST SPOTTED KNAPWEED: ITS FEEDING STRATEGY AND IMPACT ON TWO INTRODUCED UROPHORA SPP. (DIPTERA: TEPHRITIDAE)

1991 ◽  
Vol 123 (5) ◽  
pp. 1001-1007 ◽  
Author(s):  
J.M. Story ◽  
K.W. Boggs ◽  
W.R. Good ◽  
P. Harris ◽  
R.M. Nowierski
Keyword(s):  
Biological Control ◽  
Seed Dispersal ◽  
Pacific Northwest ◽  
Biocontrol Agent ◽  
Feeding Strategy ◽  
Centaurea Maculosa ◽  
Spotted Knapweed ◽  
Seed Head ◽  
The Pacific ◽  
Normal Seed

AbstractMetzneria paucipunctella Zeller is a seed head moth introduced for biological control of spotted knapweed, Centaurea maculosa Lamarck, in the Pacific Northwest. A cage study was conducted in Montana in 1987 and 1988 to assess the feeding strategy of the M. paucipunctella larva and its impact on two seed head flies, Urophora spp., also introduced on spotted knapweed. Each moth larva destroyed an average of 8.13 knapweed seeds. Most of the seeds were destroyed prior to seed dispersal in early September but the remaining seeds were attacked in the spring of the following year. Each larva tied an average of 7.0 seeds with silk webbing which allowed for feeding long after normal seed dispersal. Seed survival in cages containing both the moth and the two fly species (4.71 seeds per head) was significantly less than in fly-only cages (9.75 seeds per head). The moth larvae caused extensive mortality to the two Urophora species, especially during the spring months. Moth-caused mortality to U. affinis larvae increased from 19% during June through October to 67% in May of the following year. Mortality to U. quadrifasciata also occurred but did not increase significantly in the spring. Data from 10 field sites showed very little association between M. paucipunctella and the two Urophora species which suggests that the unnatural conditions associated with the cages did not increase the incidence of joint moth and fly attack to individual seed heads. The moth is a valuable biocontrol agent as it is contributing significantly to the overall consumer pressure on spotted knapweed seed heads.

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