Effect of environmental factors on seed germination and seedling emergence of invasive Ceratocarpus arenarius. Weed Res

Weed Research (Impact Factor: 1.69). 02/2012; 52(1):50-59. DOI: 10.1111/j.1365-3180.2011.00896.x


Ceratocarpus arenarius is a problematic and noxious
weed of dryland farming in North Khorasan, Iran.
Experiments were conducted to investigate the mecha-
nism of seed dormancy, as well as the effect of
environmental factors on germination and emergence
of this species. Results showed that the pericarp is the
major obstacle to seed germination; seeds without an
intact pericarp had germination rates exceeding 90%.
Ceratocarpus arenarius had identical germination rates
in either light ⁄ dark and continuous dark conditions,
indicating that this weed species is non-photoblastic.
Germination was >35% over a range of alternating
light ⁄ dark temperatures (10 ⁄ 5, 20 ⁄ 10, 25 ⁄ 15, 30 ⁄ 20 and
35 ⁄ 25�C), with maximum germination (96%) at
25 ⁄ 15�C. Ceratocarpus arenarius seeds germinated at
rates >20% in high levels of salinity (800 m M ) and
osmotic potential ()1 MPa), indicating that this species
is tolerant to saline conditions and drought stress during
germination and early seedling growth. Maximum
germination of C. arenarius seeds occurred at a pH
range of 7–9. Seedlings emerged from burial depths
ranging from 0 (without covering with filter paper) to
6 cm, and the maximum emergence (94%) was observed
in seeds placed on the soil surface covered with three
layers of filter paper. This suggests that minimum- and
no-till systems would increase seedling emergence of this
species through maintaining crop residues and seeds on
the soil surface. These attributes, coupled with tolerance
to salinity and drought stress during germination,
should be taken into account when managing C. arena-

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Available from: Seyed Vahid Eslami, Apr 22, 2014
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    • "In line with the studies conducted by Gulzar & Khan (2001), Wei et al. (2008), Ebrahimi & Eslami (2011) and Giménez et al. (2013), who observed that an increase in salinity causes a decrease in germination rate and germination speed, and even complete inhibition when the salt tolerance limit of the species is exceeded, we can confirm that the germination of Limonium insigne is affected by an increase in salinity. "
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    ABSTRACT: Limonium insigne (Plumbaginaceae) is a perennial halophyte endemic to the SE of the Iberian Peninsula. Experiments were conducted to determine the effects of different salinities (0, 100, 200 and 400 mM NaCl) on the seed germination of L. insigne under different temperature regimes (20/10, 25/15, 30/20 and 35/25 °C), both in a 14 h light and 10 h dark photoperiod. Seed germination of L. insigne was affected significantly by salinity levels, temperature and their interaction. Maximum germination was observed in the least saline media (100 mM NaCl) and distilled water (0 mM NaCl) at 20/10 °C temperature. No seeds germinated at concentrations higher than 200 mM NaCl at the highest temperature (35/25 °C). The increase in salinity delayed the beginning and ending of germination, reduced final germination percentage and increased mean time to germination. The rate of germination decreased with an increase in salinity and temperature.
    Pakistan Journal of Botany 01/2015; 47(3):807-812. · 0.82 Impact Factor
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    • "The authors made a mass collection of seeds (dispersal units), presumably a mixture of our units b – f (Fig. 1). They (Ebrahimi and Eslami, 2012) subsequently removed the pericarp ( probably bracteoles) from the fruits [ probably fruits (utricles) with enclosing bracteoles] and used the seeds ( probably utricles without bracteoles) in the majority of their germination tests. They erroneously concluded that their fruits have physical dormancy, which is not known to occur in Amaranthaceae (including Chenopodiaceae) (Baskin et al., 2000). "
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    ABSTRACT: Background and aims: Several studies have demonstrated trade-offs between depth of seed dormancy and dispersal ability for diaspore-dimorphic species. However, relatively little is known about trade-offs between these two life history traits for a species that produces more than two diaspore morphs. The aim of this study was to investigate the relationship between seed dormancy and dispersal in Ceratocarpus arenarius, an amphi-basicarpic cold desert annual that produces a continuum of dispersal unit morphs. Methods: A comparison was made of dispersal and dormancy breaking/germination responses of dispersal units from ground level (a), the middle of the plant canopy (c) and the top of the plant canopy (f). Various features of the morphology and mass of dispersal units and fruits (utricles) were measured. The role of bracteoles in diaspore dispersal by wind, settlement onto the soil surface and dormancy/germination was determined by comparing responses of intact dispersal units and fruits. Movement of dispersal units by wind and animals, seed after-ripening, germination phenology and the presence of water-soluble germination inhibitors in bracteoles were tested using standard procedures. Key results: Dispersal units a, c and f differed in morphology and mass; in the majority of cases, extremes were exhibited by a and f, with c being intermediate. Overall, relative dispersal ability was f > c > a, whereas relative intensity of dormancy was a > c > f. Bracteoles increased dispersal distance by wind, enhanced settlement of diaspores onto the soil surface and mechanically inhibited germination. Conclusions: The results provide evidence for a model in which there is a continuous inverse-linear relationship between diaspore dispersal ability and depth of dormancy. Thus, dispersal unit heteromorphism of C. arenarius results in a continuum, from no dispersal ability/high dormancy (dispersal unit a) to high dispersal ability/low dormancy (unit f), which may be a bet-hedging strategy in the cold desert environment.
    Annals of Botany 11/2013; 112(9). DOI:10.1093/aob/mct240 · 3.65 Impact Factor
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    ABSTRACT: Emex spinosa and Emex australis are invasive dicotyledonous weeds. The effects of various environmental factors on the germination of these weeds were investigated under laboratory and glasshouse conditions. Germination response of both species was lower at warmer temperature, and maximum germination was recorded at 20/12°C (day/night). Light stimulated germination in both species, but considerable germination also occurred under darkness. More than 80% of E. spinosa seeds germinated at pH between 6 and 9, whereas E. australis seeds germination was considerably decreased at pH 9. Emex spinosa was fairly tolerant to salinity as compared with E. australis and germination (21%) of E. spinosa occurred even at 200 mm NaCl. Both species were sensitive to osmotic stress, but E. spinosa tolerated more osmotic stress than E. australis. Temperature above 20/12°C (day/night) and low osmotic potential increased time to start germination and mean germination time (MGT), as well as decreased germination index (GI) of both species. Darkness resulted in increased MGT and decreased GI in both species when compared with 10 h photoperiod. Salt stress strongly increased time to obtain 50% germination and reduced GI of both species. In both species, an increasing burial depth decreased emergence percentage and emergence index and increased time to start emergence, although some seed emerged even at 10 cm burial depth. It was concluded that both species can germinate over a wide range of environmental conditions. However, E. australis was more sensitive under adverse environmental conditions compared with E. spinosa. This information on germination ecology may aid in developing tools and strategies for management.
    Weed Research 09/2014; 54(6). DOI:10.1111/wre.12111 · 1.69 Impact Factor
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