Table 1.
Seed mass, germination cardinal temperatures and base temperature values for the 36 cover crop species.
Fig 1.
Influence of temperature on final germination percentage for six cover crop species, showing two contrasting responses (a and b).
Fig 2.
Variation in germination dynamics for Brassicaceae cover crops at a) 26.7°C and b) 11.5°C and for Poaceae cover crops at c) 26.7°C and d) 11.5°C.
Crosses represent observed data and lines represent fitted Gompertz functions.
Fig 3.
Curves fit to observed germination rates for four fractions percentages of the seed population, 20% (◊), 30% (Δ), 40% (x) and 50% (■), according to temperature, for Brassica napus (Brassicaceae), Lolium multiflorum (Poaceae), Trifolium alexandrinum (Fabaceae) and Polygonum fagopyrum (Polygonaceae).
Fig 4.
Linear relationships fit between observed germination rate and temperature for four fractions percentages of the seed population, 20% (◊), 30% (Δ), 40% (x) and 50% (■), for Brassica napus (Brassicaceae), Lolium multiflorum (Poaceae), Vicia sativa (Fabaceae) and Polygonum fagopyrum (Polygonaceae).
Fig 5.
Examples of the influence of water potential (MPa) on final germination percentage of four species from various families.
Fig 6.
Base water potential for germination calculated for the 36 cover crops.
Patterns and shades of gray correspond to botanical families. Data are the means of both 20th and 30th percentiles.
Fig 7.
Hierarchical classification based on cardinal temperatures (T0, Tmax and Topt) and base water potential estimated on 36 cover crops using the Ward method (P<0.05).
Solid lines represent distances between species of each of five functional groups (FG), and dashed lines represent distances between FGs. See Table 1 for the definition of species abbreviations; ‘Bra.’ is ‘Brassicaceae’, ‘Fab.’ is ‘Fabaceae’, ‘Poa.’ is ‘Poaceae’ and ‘Oth.’ is ‘Other families’.
Table 2.
Mean (± 1 standard deviation) cardinal temperatures and base water potential of the species in each functional group defined from hierarchical classification.
Table 3.
Cardinal temperatures for germination and emergence in the field (Tb-emerg) from the literature for cover crop species in this study.