The Plant

A sure way to identify plants is by their chromosomes. The earliest wheat ancestors contained 14 chromosomes, which means they were "diploid." Early wheat plants looked like grass and had fragile stems with hulls that clung to the grain. This made them hard to thresh but perfect for reseeding themselves.

Primitive women first gathered einkorn, or Triticum monococcum (trit'-i-cum mahn-uh-kah'-cum), selecting it for its larger seeds and ease of threshing and harvesting. Their success led early humans away from hunting societies as the new agrarian communities thrived on cultivated crops.

A natural outcross between einkorn and the 14-chromosome Triticum spletoides (trit'-i-cum spel-toy'-dees) produced a wild wheat called Triticum turgidum (trit'-i-cum tur'-ji-duhm), which had 28 chromosomes, making it a tetraploid. This new wild species led to emmer, which was soon cultivated throughout the Middle East. The durum wheat now grown in the United States to make pasta and couscous was originally selected from the wild emmer wheat with large easy-to-thresh grains.

Modern bread wheat varieties have 42 chromosomes. These wheats evolved from a natural outcross between emmer wheat and another diploid wheat, Triticum tauschii (trit'-i-cum tow'-she-eye). This wheat was the source of the unique glutenin genes that give bread dough the ability to form gluten. Gluten provides bread dough the elasticity it needs to trap gas produced by fermenting yeast and therefore to "rise" or expand.

The wheat plant grows to a height of between 24 inches for dwarf varieties to 36 inches and even seven feet in some very old varieties. The principal parts of the plant area the roots (between three to eight feet in depth), the culms (stems), leaves, and spikes (head).

Graphic - Parts of the wheat grain head

Today, the grain head, not the straw or dried stem, is the goal for production, so the shorter varieties are much more popular with farmers. Shorter stems stand better and don't bend as easily, making them less vulnerable to wind or rain damage and easier to harvest.