Leaf Appearance Rates of Two Winter Wheat Cultivars under High Carbon Dioxide Conditions

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Abstract
The mechanisms describing leaf appearance and tillering are vital to the modeling of wheat canopy development. How these two factors will be affected by increasing global atmospheric [CO2] in cool or warm climates is not fully understood. Two southeastern USA adapted wheat (Triticum aestivum, L.) cultivars, Coker 762 and Stacy, were grown under nearly nonlimiting conditions including elevated [CO2] (600 μL L−1) and under six air temperature regimes (ranging from 4/−1 to 18/7 °C d/night and progressively increasing to 16/4 to 29/18 °C d/night during the season) to observe leaf and tiller appearance rates and to compare tillering rates to those predicted by the Fibonacci series as approximated by Binet's equation. Both cultivars exhibited an abrupt one‐time change in their phyllochron interval for all six temperatures. This change occurred just prior to double ridge formation. The vegetative growth phase phyllochron interval of the two cultivars was significantly different only in the (21/10 °C) temperature treatment. In the two lowest temperature treatments (16/4 and 18/7 °C), the cultivars differed in phyllochron interval during the reproductive growth phase. The tillering rate of wheat followed closely the theoretical development predicted by Binet's equation during the vegetative phase of development.