Abstract
Seedlings of Secale cereale cv. Rheidol and Triticum aestivum cv. Mardler were grown at shoot/root temperatures of 20/20 °C, 20/8 °C and 8/8 °C. During vegetative growth both cereals produced leaves, tillers and roots in a defined pattern, at a species-specific rate which was linearly related to the temperature of the shoot meristem. Thus, plant development could be standardized on a temperature × time (°C d) basis despite contrasting growth-temperature treatments. When compared at a similar developmental stage, the cooling of whole plants or of plant roots resulted in an increase in the d. wt: f. wt ratio of both shoot and root tissues, a decrease in the length of both the longest shoot and root, and the development of broader and thicker leaves. Although the effects of temperature on developmental characteristics could be accurately predicted by an empirical relationship, the effects on morphological characteristics could not.