In the vegetative phase, shoots consist predominantly of leaf blades. Leaf blade collars remain nested in the base of the shoot and there is no evidence of sheath elongation or culm development. (Read more)
In response to critical temperature regimes, daylengths, and necessary leaf blade area for sensing these climatic variables, the apical meristem is gradually converted from a vegetative bud to a floral bud. This is called floral induction. This conversion phase is termed the transition phase.
During the transition phase, leaf sheaths begin to elongate, raising the meristematic collar zone to a grazable height.
Culm internodes also commence elongatation in an ""un-telescoping"" manner beginning with the lowermost internode thereby raising the meristematic zone (floral bud and leaf bases) to a vulnerable position. (Read more)
Reproductive (flowering) Phase
The flowering phase commences with the conversion of the shoot apex from a vegetative condition to a floral bud. Much of this is unseen until the emergence of the seedhead from the sheath of the flag leaf (boot stage). The almost sudden appearance of the seedhead is caused by rapid elongation of the peduncle (uppermost internode of the culm). Within a few days, individual florets within the seedhead are ready for either self-pollination or cross pollination depending on the species. For cross pollination to occur, the floral bracts (lemma and palea) must be spread apart to allow for the exchange of pollen. Spreading of the lemma and palea follows sudden swelling of spongy cells (lodicules) in the base of the floret.
Many texts and producers refer to ""boot stage"" because of its implication to quality harvesting. The boot stage is defined as the time when the seedhead is enclosed within the sheath of the flag leaf. It is one part of the reproductive phase.
Anthesis is defined as the shedding of pollen by anthers onto receptive stigmas. It is another part of the reproductive phase.