Flowering and fertilisation

While the ear remains within the protection of the leaf sheath, the stage known as 'booting', the flower parts are steadily maturing. Each spikelet produces 8 -12 florets (this is many more than it can support), but most of these abort before flowering starts. There are photographs of the changes in the growing point as it matures in the section 'Development of the Wheat Apex'.

Flowering or Anthesis takes place a few days after the ear emerges from the leaf sheath. The flower stalk (peduncle) will have lifted the ear up into the top of the crop canopy a few centimetres above the last leaf (flag leaf) of each tiller. In open flowering wheat types a number of co-ordinated events take place within the space of a few minutes. The stamen filaments grow rapidly to six or eight times their original length. At the tip of each anther two pores appear through which the pollen will be shed. At the base of each floret the lodicules swell rapidly forcing apart the lemma and palea. This allows the stamens to emerge and dangle freely from the floret. The pollen from the anthers falls onto the receptive feathery stigmas of the carpel which have unfolded to receive it (There are more photographs of pollen shed in the section, Photographs of Pollen Release). Inside the carpel a double fertilisation event takes place within the embryo sac. One pollen nucleus fuses with the egg cell which will subsequently divide to form the diploid embryo. A second pollen nucleus fuses with the two polar nuclei in the embryo sac (called the second polar event). These nuclei will subsequently divide and cellularise to form the triploid endosperm. The embryo sac already contains antipodal cells which will fuel the next stages of grain development.