Temperature and Daylength Interaction on Phyllochron in Wheat and Barley
An understanding of how environment controls the initiation and development of leaves is required to construct dynamic crop simulation models. The leaf development process is poorly understood in cereals. This study was designed to investigate the interaction of temperature and daylength on the leaf phyllochron in winter wheat (Triticum aestivum L.) and spring barley (Hordeum vulgare L.). Growth chamber experiments were conducted at all combinations of three temperatures (10,15,20 °C) and four daylengths (6,10,14,18 on four wheat and four barley genotypes. Wheat and barley had a constant phylloehron (the number of degree-days elapsed between successive leaves on a culm) at a given temperature and daylength combination. However, the phyllochron varied among genotypes and among temperature and daylength combinations. Phyllochron increased as temperature increased or as daylength decreased. The combined action of temperature and daylength on phyllochron could be quantified in a single term, the thermo/photo ratio (the ratio of daily degree-days to daylength). The phyllochron for all genotypes in this study was linearly related to the thermo/photo ratio in all the temperature-daylength combinations, with R2 values not less than 0.94. An evaluation of published field data for barley planted on different dates in two growing seasons suggests that the thermo/ photo ratio may be adequate to explain the different phyllochron values typically observed in such experiments. Our results suggest that cultivar specific coefficients will be necessary to predict the cultivar response of phyllochron to the thermo/photo ratio in wheat and barley.
Copyright © 1989 by the Crop Science Society of America, Inc.