Interaction of temperature and daylength on leaf appearance rate in wheat and barley

A common way of describing wheat phenology during the leaf development stag e is by reporting the number of leaves on the main stem. The ability to pre dict the timing of successive leaf appearance is important because it impac ts on the timing of certain developmental stages of the plant and on the ra te of leaf area expansion. Therefore, most crop models use leaf appearance rate to model development during early phases of plant growth. However, man y researchers have expressed frustration with our inability to predict the rate of leaf appearance. Temperature and daylength are the two major factor s that influence the leaf appearance rate. In this paper, we demonstrated h ow plant response to daylength in winter wheat (Triticum aestivum L.) and s pring barley (Hordeum vulgare L.) can be incorporated into the non-linear B eta function to describe the interactive effect of temperature and daylengt h on leaf appearance rate. The model predictions of leaf appearance rate ag reed very well with the observed values measured in controlled environments . The model requires four genetic coefficients for each cultivar to predict the combined effect of temperature and daylength on leaf appearance rate. The coefficients can be determined from experiments in controlled environme nts with varying temperatures at constant daylength, and varying daylength at the optimum temperature for leaf appearance. The cultivar-specific model s are necessary to assess cultivar adaptation to specific locations. Other genetic and environmental factors also affect leaf appearance rate. Thus, t hose factors may be needed to further refine the model to predict leaf appe arance in the field. (C) 1998 Elsevier Science B.V. All rights reserved.