COORDINATION OF STEM ELONGATION AND ZADOKS GROWTH-STAGES WITH LEAF EMERGENCE IN WHEAT AND BARLEY

Leaf emergence, apex development stage, internode length and Zadoks pr incipal growth stage 3 were measured over 3 years at several sites. In ternode elongation and Zadoks score were strongly related to the numbe r of emerged culm leaves. The final length of the most basal internode was very variable and contributed to variation in the relationship be tween Zadoks stage 30 and the number of emerged culm leaves. Variation in the length of the basal internode was related to the final number of culm leaves. Most plants had six culm leaves but the number of leav es was affected by sowing date. In an experiment where sowings were ma de from September to March, stem elongation and Zadoks stage 30 starte d at a later stage of apex development in later sowings. Recognition a nd prediction of culm elongation and number of emerged culm leaves is important for the application of growth regulator and fungicides. Comb ined with functions to predict the rate of leaf emergence and final nu mber of leaves, the relationships described in this paper may enable Z adoks principal growth stage 3 and number of emerged culm leaves to be predicted.