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Mathematical Description of the Influence of Temperature and Seed Quality on Imbibition by Seeds of Corn (Zea mays L.)¹

Imbibition by seeds of corn (Zea mays L.) was described by the equation W=f(t) — (-W₀')/exp(kt) where W is the water content of the seed on a dry weight basis, f(t) = bt and is the asymptote of the exponential curve where a is the asymptote at time t= 0 and b the slope, and W₀' is an adjusted initial water content. The rate constant k was shown to be related to the permeability of the seed to water, to the initial water capacity of the seed, and b to the rate of change in the water capacity of the seed during imbibition which was related to elongation of the radicle and shoot. The initial water content, W₀, was linearly related to the relative humidity of the atmosphere in which the seed had equilibrated. The parameters k, b, and were not significantly affected when W₀ varied from 2.0 to 13.9%. Both k and b increased exponentially with temperature with a Q₁₀ of 2.37 and 1.85, respectively, over the range 12 to 31C and 12 to 32.5, respectively; there was a sharp departure from the exponential relationship outside these ranges of temperature. The energy of activations of the exponential and linear phases of imbibition were 15.3 and 9.1 kcal/mole, respectively. The parameter varied less dramatically with temperature and was fitted by a fourth order polynomial in temperature with a minimum at 26C. The parameters of the imbibition curve also were a function of age and variety of the seed. A survey of the literature showed that the equation for imbition could be used to describe imbibition of a wide range of seeds. The equation will be used in a mathematical model to predict germination and emergence of corn in a changing environment.

Key Words: Sweet corn • Relative humidity • Water content • Germination • Permeability • Energy of activation

² Formerly Assistant Professor, Department of Land Resource Science, University of Guelph, Ontario, Canada. Present address: Department of Agronomy, University of Western Australia, Nedlands, W.A. 6009, Australia.

Received for publication January 5, 1972.