Tiller axis observations for perennial ryegrass (Lolium perenne) and tall fescue (Festuca arundinacea ): Number of active phytomers, probability of tiller appearance, and frequency of root appearance per phytomer for three cutting heights

Abstract Counts of phytomers in various developmental stages from formation at the apical meristem to senescence following root formation and death are presented for perennial ryegrass and tall fescue. Total number of active phytomers on tiller axes averaged 18.7 for perennial ryegrass and 16.3 for tall fescue ( P < 0.05) and decreased with increasing cutting height ( P < 0.05). Ryegrass maintained more primordia than tall fescue between the apical meristem and the emerging leaf, but had fewer fully emerged live leaves per tiller. Numbers of tillers and roots formed per phytomer are reported as nodal probabilities and nodal frequencies, respectively. The nodal probability of daughter tiller formation T n varied over time from 0 to 0.7, and was highest when swards had a low leaf area index shortly after establishment. Nodal frequency of root formation R n was relatively constant at around 1.5 per phytomer for both ryegrass and tall fescue. The first root was most commonly found at the phytomer immediately below the last live leaf. The number of phytomers on the tiller axis bearing live roots is approximately double the number bearing live leaves, indicating slower turnover rate of roots than leaves.