Early growth and tillering

Diagrams and pictures


Leaf 1 emerges at soil level and gets to work. It has a slightly blunt tip compared to leaves 2 and 3 which follow. During germination the first true leaf, leaf 1, is protected by the coleoptile sheath.
The change from the vegetative to the floral state. The apical dome initiates primordia at a faster rate than they can turn into leaf primordia with the result that undifferentiated primordia stack up on the elongated apex. The development of the lower 'leaf' ridges, which are poorly defined at the top of the apex, will be arrested. The tissue between these ridges now grows and will become the 'spikelet' ridge. This stage is know as double ridge and is the key to the timing of some husbandry events, such as fertilizer application.
Go to the special section of Images of the Developing Apex to see how the spikelet ridge changes and adds glume, lemma and floret primordia.
At the tip of each growing shoot the apical meristem is producing new leaves. The apex on the left is vegetative; new leaf primordia are inserted on opposite sides of the apical dome. The apex on the right has extended very slightly. The lower primordia will still become leaves but soon spikelet primordia will develop between the 'leaf' ridges. Go to the special section for more images of the Developing Apex.
Leaf 2 has a pointed tip. The coleoptile, which was present in the seed and protected the emerging shoot, stops growing and remains at the soil surface.
The first three leaves have emerged, the fourth is tucked inside the third. The first primary tiller is just showing in the axil of leaf 1. Leaf 1 and leaf 2 have suffered wind damage over the week-end.
Mid-winter and day length is increasing. The mainstem is the strongest of the shoots and primary tillers have been produced in the axils of its lowest leaves. The tillers have grown well but the mainstem leaves subtending them have suffered from the weather and disease and are difficult to identify as they rot away. The mainstem has produced a total of 14 leaves, 10 of which are fully emerged. At its apex the meristematic dome changes from leaf production to spikelet production; no more leaves will be produced. The primary tillers produce fewer leaves than the mainstem with the result that all the ear bearing stems will flower together in the spring.
There are also secondary tillers associated with tiller 1, tiller 2, tiller 3 and tiller 4.
In midwinter, when the apex changed from leaf production to spikelet production, we recorded the following leaf and tiller numbers.
The mainstem from this autumn sowing produced 14 leaves. Tiller 1 produced 12 leaves and 3 secondary tillers; Tiller 2 produced 11 leaves and 2 secondary tillers. Tiller 3 produced 10 leaves and 2 secondary tillers and Tiller 4 produced 9 leaves and 1 secondary tiller.
Early winter and the plant has adopted a characteristic prostrate form. Four leaves are fully emerged and tillers are seen in the axils of leaf 1 and leaf 2. In this plant the coleoptile tiller has also grown. The coleoptile is a robust structure and its purpose is to protect the first true leaf until it reaches the soil surface. It, and its tiller bud, are present in the dormant seed. There is an internode associated with the coleoptile and, if the seed is sown deeply, this internode will grow to raise the crown of the plant, positioned at leaf 1, to just below soil level. The coleoptile tiller may grow to produce an ear but this usually yields less grain than the tiller from leaf 1.
The plant, above, has been separated into its component shoots; the mainstem and the primary tiller groups. The mainstem still has tiller 5 attached and tiller 6 and tiller 7 can be seen in the leaf axils.