Seed germination and seedling emergence of velvetleaf (Abutilon theophrasti) and Barnyardgrass (Echinochloa crus-galli)

Abstract

-Abutilon theophrasti and Barnyardgrass (Echinochloa crus-galli) are major weeds that affect cropping systems worldwide. Laboratory and greenhouse studies were conducted to determine the effects of temperature, pH, water and salinity stress, and planting depth on seed germination and seedling emergence of Velvetleaf and Barnyardgrass. For Velvetleaf, the base, optimum and ceiling germination temperatures were estimated as 5, 35 and 48 o C, respectively. Seed germination was sensitive to drought stress and completely inhibited by a potential of -0.6 MPa, but it was tolerant to salinity. Salinity stress up to 45 mM had no effect on the germination of Velvetleaf, but germination decreased with increasing salt concentration. Drought and salinity levels for 50% inhibition of maximum germination were -0.3 MPa and 110 mM, respectively. Seed germination of Velvetleaf was tolerant to a wide range of pH levels. For Barnyardgrass, the base, optimum and ceiling germination temperatures were estimated as 5, 38 and 45 o C, respectively. Seed germination was tolerant to drought stress and completely inhibited by a potential of -1.0 MPa. Salinity stress up to 250 mM had no effect on seed germination. Drought and salinity levels for 50% inhibition of maximum germination were -0.5 MPa and 307 mM, respectively. A high percentage of seed germination was observed at pH=5 and decreased to 61.5% at acidic medium (pH 4) and to 11% at alkaline medium (pH 9). Maximum seedling emergence of Velvetleaf and Barnyardgrass occurred when the seeds were placed on the surface of the soil or at a depth of 1 cm.Keywords: pH, planting depth, seed germination, temperature, weed.RESUMO -Abutilon theophrasti e Echinochloa crus-galli são as principais plantas daninhas que afetam os sistemas de cultivo em muitas partes do mundo. Estudos em laboratório e em casa de vegetação foram conduzidos para determinar os efeitos da temperatura, pH da água e estresse salino e da profundidade de semeadura na germinação e na emergência das plântulas de A. theophrasti e E. crus-galli. Para A. theophrasti, as temperaturas de base, ótima e de teto de germinação foram estimadas em 5, 35 e 48 o C, respectivamente. A germinação das sementes foi sensível ao estresse hídrico e inibida completamente por um potencial de -0,6 MPa, mas foi tolerante à salinidade. Estresse salino de até 45 mM não teve nenhum efeito sobre a germinação de A. theophrasti, porém esta diminuiu com o aumento da concentração salina. Os níveis de seca e de salinidade para 50% de inibição da germinação máxima foram de -0,3 MPa e 110 mM, respectivamente. A germinação das sementes de A. theophrasti foi tolerante a uma vasta gama de níveis de pH. Para E. crus-galli, as temperaturas de base, ótima e de teto de germinação foram estimadas em 5, 38 e 45 o C, respectivamente. A germinação das sementes foi tolerante ao estresse hídrico e inibida completamente a um potencial de -1,0 MPa. Estresse salino de até 250 mM não teve efeito sobre a germinação das sementes. Os níveis de seca e de salinidade para 50% ...

Base temperatures for germination of selected weed species in Iran

“…amaranthus hybridus had the lowest t b values among (Holt & Orcutt 1996;Masin et al 2010). Regarding e. crus-galli, values of t b in agreement with the findings of the present study were estimated by Steinmaus et al (2004) and Masin et al (2010) for Californian and Italian populations, while significantly lower t b of about 6 and 5°C were reported for a French and Iranian population, respectively (Guillemin et al 2013;Sadeghloo et al 2013). …”

“…The range of t b values estimated for a. theophrasti (3.5 ± 1.15°C to 4.9 ± 0.16°C) was in complete agreement with the results of previous studies on an Iranian population (Sadeghloo et al 2013), but also on European populations (Masin et al 2010;Loddo et al 2013), while Dorado et al (2009b) reported a value of around 7°C as t b for a Spanish population. Results obtained for a. albus (t b from 10.4 ± 0.42°C to 13.1 ± 0.46°C) confirmed previous findings by Steckel et al (2004), who observed almost no germination for this species at 10°C, while higher values of t b , ranging from 14°C to 17°C, were estimated by Steinmaus et al (2000).…”

“…This result was not presumable a priori since values of t b for local populations had previously been studied only for a. theophrasti and e. crus-galli (Sadeghloo et al 2013), while for the remaining species the available t b values were determined in other geographical areas such as the US or Europe. However, further experiments are necessary to estimate other parameters required for the Alertinf model, such as base water potential for germination (Y b ).…”

GERMINACIÓN Y EMERGENCIA DE Megathyrsus maximus VAR.maximus

“…gramíneas como Rottboellia cochinchinensis y Echinochloa crus-galli emergen hasta los 8 cm de profundidad (Bolfrey-Arku et al, 2011;Sadeghloo et al, 2013).…”

“…Por otro lado, el laboreo intensivo afecta la emergencia de plántulas, ya que las semillas quedan enterradas a diferentes profundidades (Hugo et al, 2014) y solo algunas especies pueden emerger desde una profundidad de 10 cm y superiores (Bolfrey-Arku et al, 2011;Sadeghloo et al, 2013). Por el contrario, la labranza cero tiende a aumentar el banco de semillas en los primeros centímetros de suelo, por lo que la densidad de emergencia de plántulas podría ser mayor (Singh et al, 2015).…”