A Development Scale for Perennial Ryegrass

Vernalised plants of perennial ryeg ra ss (Lolium prenne L. cv. Orasslonds Nui) were grown under controlled conditions and apical development followed by regular excision of apices, which were examined by light and scanning electron microscopy. A 12-point scale describing apical development from the vegetative stage to ear emergence has been produced that is presented in 2 forms: a developmental sequence describing organogenesis events at specific stages, and a commentary on easily recognised features of each stage. The developmental scale provides a detailed analysis that is of value as a botanical description and as a practical aid to those involved in perennial ryegrass seed production. Evaluation of the development scale in field experiments showed an excellent relationship between the log10 (stem length + I) and apical stage. The linearity o f the adjusted development scale was of considerable value in data analysis and interpretation of vegetat ive and reproductive gr owth stages resu lting from the application of agronomic treatments.