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Phyllochron Response to Vernalization and Photeperiod in Spring Wheat

Cereal Program, ICARDA, P.O. Box 5466, Aleppo, Syria

Ralph A. Fischer

CIMMYT, APDO, Postal 6-641, 06600, Mexico, D.F.

^* Corresponding author.

An understanding of how environment controls the initiation and development of the leaf is required to construct dynamic crop simulation models. The aim of this study was to determine the effect of vernalization and photoperiod on total number of leaves at anthesis, leaf emergence rate, and phyllochron in 20 spring wheat genotypes (Triticum aestivum L.). An experiment was conducted under greenhouse conditions during spring 1992 at ICARDA, Tel Hadya, Syria, with all combinations of three photoperiods (8-, 12-, and 16-h daylength) and two vernalization treatments (vernalized and nonvernalized). Total number of leaves on the main stem at anthesis decreased with increasing photoperiod. Vernalization reduced the total number of leaves on main stem at anthesis in the eight vernalization-sensitive genotypes. Leaf number on the main stem was linearly (r = 0.99) related to accumulated growing degree days (°C d). Genotypes differed in leaf emergence rates. Leaf-emergence rate increased with increasing photoperiod. Phyllochron decreased with increased daylength from 124 °C d leaf^–1 at 8 h to 97 °C d leaf^–1 at 16-h photoperiod. These results suggests that, to model leaf appearance and canopy development in wheat, genotypic coefficients of phyllochron need to be determined in relation to photoperiod. Additionally, the effect of vernalization at inductive photoperiods on the phyllochron in genotypes adapted to heat-prone tropical environments needs further study.

Received for publication April 8, 1994.