Temperature Parameters Useful for Modeling the Germination and Emergence of Pearl Millet

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Abstract
The modeling of germination and seedling emergence is required for the construction of a simulation model of pearl millet [Pennisetum americanum (L.) Leeke]. This study provides the temperature parameters necessary to model these processes. Seed of BJ104 pearl millet were germinated in incubators at six controlled temperatures (15, 20, 25, 30, 35 and 40 °C). Germination percentage and coleoptile lengths were measured over time in each temperature regime. Germination percentage at 5 d after the commencement of imbibition was not affected by temperature. Cubic polynomials described the rates of development for germination and coleoptile elongation over the temperature range of 15 to 40 °C. The relationships between rate of development for germination and the lag stage prior to linear elongation of the coleoptile and temperature were linear only between a base of 16 °C and an optimum of 35 °C. The thermal time for the growth stages from planting to 50% germination, germination to the start of linear coleoptile extension, and the duration of linear coleoptile elongation from seed depth until 50% emergence were 5.3 ± 0.4, 7.5 ± 0.4, and 0.82 ± 0.06 degree‐days (°C‐d)mm−1, respectively. It is proposed to use these parameters in a crop simulation model to predict emergence of pearl millet seedlings.