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

Weed Research (Impact Factor: 2.02). 02/2012; 52(1):50-59. DOI: 10.1111/j.1365-3180.2011.00896.x

ABSTRACT 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-

  • [Show abstract] [Hide abstract]
    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; · 2.02 Impact Factor


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May 29, 2014