Temperature - germination responses of sunflower (Helianthus annuus L.) genotypes
2000
Khalifa, F.M. (University of Gezira, Wad Medani (Sudan)) | Schneiter, A.A. | Eltayeb, E.I.
Seed germination of six sunflower (Helianthus annuus L.) hybrids was investigated across a range of eleven constant temperatures between 5 deg C and 45 deg C. Large temperature differences in germination rate l/t (dE-1), cardinal temperature (deg C) and thermal time 0 (deg cd) were observed among hybrids. Base temperatures (Tb) varied between 3.3 deg C and 6.7 deg C whereas maximum germination temperatures (Tm) varied between 41.7 deg C and 48.9 deg C. Final germination fraction was attained at 15 deg C - 25 deg C whereas the maximum rate of germination was attained at 30.4 deg C - 35.6 deg C. The maximum germination rate of hybrid USDA 894, the cultivar with the slowest germination rate, was only 50% of that of hybrid EX 47. The low Tb and high Tm of sunflower appear to be one of the factors which explain the successful adaptation of sunflower to a wide range of temperature. These findings are discussed in relation to the origin of the crop and its wide adaptations in diverse habitats and climatic zones.
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