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A grass is a flowering plant in the family Poaceae, which includes maize, rice, wheat and bamboos. Typical grass leaves have a sheath clasping a jointed plant stem and a blade extending away from it; a ligule often occurs at their junction. The flowers are grouped into spikelets, and the characteristic fruit is a caryopsis.^[ref]

Recognizing the family requires more than seeing narrow green leaves. Many grass stems have hollow intervals between solid joints, but maize has substantial internal tissue and bamboos can be woody. Shared floral organization provides a more reliable basis for comparison than one vegetative feature. Grass biology connects the structure of a lawn to the grain crops that feed people.

Triticum is the taxonomic genus containing wheat, within the grass family Poaceae. A taxonomic genus groups related species; it is consequently broader than Triticum aestivum, the species used as common bread wheat. Keeping these ranks separate prevents a result measured in one cultivated species from automatically becoming a statement about every Triticum.^[ref]

The genus is especially useful for studying polyploidy. In bread wheat, three related ancestral genomes are represented twice, conventionally written AABBDD. Seven chromosomes per ancestral set give $2\times (7+7+7)=42$ chromosomes. The letters label related inherited sets; they do not mean that there are only three chromosomes.^[ref]

During meiosis, a chromosome must distinguish its homologous chromosome from similar chromosomes belonging to the other ancestral sets. Comparing chromosome pairing in ordinary wheat with pairing after alteration of the Ph1 locus tests how this distinction is controlled. Thus Triticum connects crop classification with the cell-level problem of distributing multiple related genomes reliably between generations.^[ref]