Apical development in oats predicted by leaf stage

Phenological development of the shoot apex in three oat cultivars was monitored and related to the appearance and growth of leaves. Because oat leaves appear and expand differently from wheat leaves, a new continuous decimal leaf scale was developed for this purpose. There were usually two visible laminae expanding at the same time, until the appearance of the Bag leaf Thus, leaf tip number n + 2 became visible after leaf number n had reached its maximum length. The leaf stages corresponding to the formation of the flag leaf primordium (FP), double ridge (DR) and the formation of the terminal spikelet (TS) were strongly and linearly related to the final number of leaves, even though the leaf stage at any of these events varied substantially with sowing date. However, the number of leaves still to emerge after the specified apical events was nearly constant, regardless of sowing dates. The study showed that apical events can be predicted from observations of the leaf stage, provided that the final leaf number can be predicted. (C) 2000 Elsevier Science B.V. All rights reserved.