Herbicide-resistant (R) and –susceptible (S) <i>E. oryzicola</i> germination in response to stratification duration and water potential.

<p>Seeds were immersed in PEG solutions of 0, −0.4, −0.8 and −1.6 MPa at a constant 5°C for 3, 4, 7, 10, 14, 17, 23, 30, 57 and 92 days prior to germination at 21°C and 0 MPa. Final germination for all treatments was ≥95%. Germination rates were calculated by replicate as the inverse of median time to germination (<i>1/t₅₀</i>), which was determined from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0071457#pone.0071457.e005" target="_blank">Equation 5</a>. Seeds were germinated at 17/24°C night/day temperatures, 0 MPa and 21% oxygen. Symbols are averages of two replicates of 50 seeds per treatment. Peak GR was attained at 30, 23, 30, 23, 23 and 17 days of stratification in 0 MPa for AL, CR, HR, KS, RD and SW, respectively. The LSD_0.05 for the interaction between population, stratification duration and stratification <i>Ψ</i> was 0.06; d.f.  = 478.</p

Final germination of stratified (solid lines and symbols) and nonstratified (dashed, open symbols) seeds of herbicide-resistant (R) and –susceptible (S) <i>E. oryzicola</i> populations across a range of oxygen levels.

<p>Seeds were germinated at 25°C and 0 MPa, following three months of chilling at 3°C in water (stratified) or under dry conditions (nonstratified). Symbols represent averages of observations ±SE based on six replicate sets of 35 seeds; lines are linear regressions. The LSD_0.05 for the interaction between population and stratification treatment was  = 7% with 192 d.f.</p

Average observed (symbols) and predicted (lines) germination among herbicide-resistant (R) and –susceptible (S) <i>E. oryzicola</i> populations across a gradient of for stratified (solid) and nonstratified (open/dashed) seeds.

<p>Seeds were germinated following three months of chilling at 3°C in water (stratified) or under dry conditions (nonstratified). Hydrotime germination models were fit by replicate with the equation<i> probit(g)</i>  =  [<i>Ψ</i> – <i>θ_H</i>/<i>t_g</i>–<i>Ψ_b</i>(50)]/σ<i>_Ψb</i>, where <i>Ψ</i> is experimental water potential, <i>θ_H</i> is the hydrotime constant to germination, <i>t_g</i> is time to germination of fraction <i>g</i> of the seed population, <i>Ψ_b</i>(50) is median base water potential and σ<i>_Ψb</i> is the standard deviation in <i>Ψ_b</i> among seeds in a population. Average stratified and nonstratified root mean squared errors (RMSE) ±SE were: 0.079±0.009 and 0.082±0.009 for CR, 0.065±0.006 and 0.107±0.003 for HR, 0.082±0.005 and 0.116±0.014 for KS, and 0.077±0.006 and 0.126±0.007 for SW, respectively. Symbols represent averages of observations and bars represent SE based on six replicate sets of 35 seeds.</p

Germination rates (GR, calculated by replicate as the inverse of median time to germination (<i>1/t₅₀</i>) using Equation 5) following 24 days of stratification at three temperatures <<i>T_b</i> for germination.

<p>Herbicide-resistant (R) and –susceptible (S) <i>E. oryzicola</i> seeds were germinated at 14/26°C night/day, 0 MPa and 21% oxygen. Values are averages ±SE of 3 replicate sets of 50 seeds.</p

Maximum germination rates (GR, calculated by replicate as the inverse of median time to germination (<i>1/t₅₀</i>) using Equation 5) after stratification at 5°C under various water potentials.

<p>GR was assessed for each herbicide-resistant (R) and –susceptible (S) <i>E. oryzicola</i> population after 0, 3, 4, 7, 10, 14, 17, 28, 35, 57 and 92 days of stratification and values are averages ±SE of the maximum GR for each replicate.</p>a.<p>To meet ANOVA assumptions, a Box-Cox transformation (λ  =  −1.8) was applied.</p

Final germination of stratified (solid lines and symbols) and nonstratified (dashed lines, open symbols) seeds of herbicide-resistant (R) populations (KS and SW) and –susceptible (S) <i>E. oryzicola</i> populations (CR and HR) across a range of water potentials.

<p>Seeds were germinated for 14 days at 25°C and 21% oxygen following three months of chilling at 3°C. Symbols represent averages of 6 observations ±SE; the LSD_0.05 for the interaction between population and stratification treatment was 7% with 192 d.f.; lines are polynomial regressions.</p

Effects of alternating temperatures on final germination (G) and germination rates (GR, calculated by replicate as the inverse of median time to germination (<i>1/t₅₀</i>) using Equation 5) of herbicide-resistant (R) and –susceptible (S) <i>E. oryzicola</i>.

<p>Nonstratified seeds were germinated at 0 MPa and 21% oxygen, with temperatures either held constant at 20°C or set to 14/26°C day/night regime. Values are averages ±SE of four replicate sets of 50 seeds.</p

Parameters of the hydrotime model (Equation 2) characterizing the responses of herbicide-resistant (R) and –susceptible (S) <i>E. oryzicola</i> populations germinated at 25°C, 21% oxygen and <i>Ψ</i> of 0, −0.2, −0.4 or −0.7 MPa, after being stratified [16] or not for three months at 3°C; <i>θ_H</i> is the hydrotime constant; <i>Ψ_b</i>(50) is median base water potential, and<i>σ_Ψb</i> is the standard deviation in <i>Ψ_b</i> among seeds around <i>Ψ_b</i>(50).

<p>Models were fit for each of six replicates; values are parameter averages ±SE.</p