Structure of wheat

Wheat - structure and genetics

For those who aren't familiar with the anatomy of an 'ear' of wheat...

The ear consists of a number of individual spikelets (flower heads) set one above another along a length of stem known as the r(h)achis. Each spikelet has a single set of glumes (sheaths) enclosing up to 8 grains (each developing from a flower); each grain is enclosed in its own glumes (the lemma and palea). The glumes may have long dorsal to terminal bristles known as awns but this is now rare in modern wheat. The number of flowers/spikelet is an important character in identifying spp of wheat. Whether or not the grains are easily released from the glumes is another: 'hulled' wheats have strong glumes which hold the grains in the spikelets; 'naked' wheats are easily released even from the lemma and palea. The ease of release has implications for timing of harvest, ease of threshing, and resistance to disease/predation.

And the genetics... wheats may be diploid (14 chromosomes), tetraploid (28 chromosomes), or hexaploid (42 chromosomes). The more chromosomes, the easier it is to breed varieties suitable to local soil and climate.

Einkorn aka Small Spelt:

diploid hulled wheat with both winter and spring varieties
small bearded ears resembling those of Two-rowed Barley
fragile rachis
spikelets 2-3 flowered, producing 1 or 2 long narrow grains

Emmer: aka Small Spelt:

tetraploid hulled wheat with both winter and spring varieties, but appears to prefer spring planting in temperate climates. Not frost resistant; does not do well in humid areas.
similar to Einkorn, but the ear is larger and stouter, less flattened

Spelt aka Large Spelt:

hexaploid hulled wheat with both winter and spring varieties. It's particularly hardy and can withstand both frosts and snow in the growing season.
awned or unawned medium to long ears of very widely spaced spikelets.
glumes square-tipped.
spikelets 3-4 flowered, producing 2 long, narrow, flinty grains.

Sarah Wroot

For a much more detailed description of the underlying botanical and biochemical processes in the growth of a grain of wheat see: http://www.wheatbp.net