The mesocotyl is an embryonic organ present in Poaceae that plays an important role in seedling emergence. The elongation of this first internode contributes decisively to the coleoptile reaching the soil surface. This study examines the process of mesocotyl elongation under controlled conditions in three caryopsis collection sites of Digitaria sanguinalis (L.) Scop. originating from Spain (Barcelona and Girona) and Argentina that may have two patterns of germination: radicular or coleoptilar. The frequencies of the two germination patterns varied significantly depending on the origin. Light inhibited the elongation of the mesocotyl drastically, resulting in maximum lengths of 3.5mm, while in darkness the maximum length was 57mm. The time-course evolution displayed under dark conditions was quite similar for all sites of origin and both germination patterns; the growth rate ranged from 0.23 to 0.30mmh21. Within localities, caryopses with a coleoptilar pattern of germination showed a lower growth rate than those with a radicular one.